土井 洋平

BACKGROUND: Carbapenem-resistant Gram-negative bacilli (CR-GNB) are a major public health threat, traditionally linked to hospital settings. However, infections are increasingly reported in the community, and the clinical distinctions between community-associated (CA) and healthcare-associated (HA) infections remain unclear. METHODS: We conducted a prospective multicenter study of hospitalized patients with CR-GNB infections across 13 Japanese tertiary hospitals between April 2019 and March 2024. Infections were categorized as CA, HA, or hospital-onset (HO) using standardized criteria. We compared patient demographics, microbiological findings, infection sites, and clinical outcomes based on the setting of onset. RESULTS: Among 425 patients, 43 had CA, 59 HA, and 323 HO infections. Pseudomonas aeruginosa was the predominant pathogen in all groups. Aeromonas species were more frequently associated with CA than HO cases (23.3% of CA vs 2.2% of HO cases), whereas Stenotrophomonas maltophilia was detected almost exclusively among HO cases. Hospital-onset infections were associated with longer median hospital stays compared with CA infections (68 vs 17 days) and a trend toward higher 30-day mortality (23.9% vs 9.5%). In contrast, HA infections demonstrated no significant differences from CA infections in either hospital length of stay (23 vs 17 days) or 30-day mortality rate (10.3% vs 9.5%). CONCLUSIONS: Community-associated CR-GNB infections are an emerging concern in Japan, showing distinct pathogen profiles and infection sites compared to HO cases. Importantly, HA infections resembled CA infections in terms of clinical characteristics and outcomes, suggesting a need to reexamine the clinical relevance of current HA classification criteria for guiding therapy and risk stratification.

Antibiotic resistance is a threat to human health, yet recent work highlights how loss of resistance may drive pathogenesis in some bacteria. In two recent studies, we found that β-lactam antibiotics and nutrient stresses faced during infection selected for genetic inactivation of the Pseudomonas aeruginosa antibiotic efflux pump mexEFoprN. Unexpectedly, efflux pump mutations increased P. aeruginosa virulence during infection; however, neither the prevalence of mexEFoprN inactivating mutations in real human infections, nor the mechanisms driving increased virulence of efflux pump mutants are known. We hypothesized that human infection would select for virulence enhancing mutations. Using genome sequencing of clinical isolates, we show that mexEFoprN efflux pump inactivating mutations are enriched in P. aeruginosa isolates from cystic fibrosis infections relative to isolates from acute respiratory infections. Combining RNA-seq, metabolomics, genetic approaches, and infection models we show that efflux pump mutants have elevated quorum sensing driven expression of elastase and rhamnolipids which increase P. aeruginosa virulence during acute and chronic infections. Restoration of the efflux pump in a representative respiratory isolate and the notorious cystic fibrosis Liverpool epidemic strain reduced their virulence. These findings suggest that mutations inactivating antibiotic resistance mechanisms could lead to greater patient mortality and morbidity.

Carbapenem-resistant Acinetobacter baumannii (CRAb) is a challenging, environmentally hardy organism with a propensity to spread within hospitals and a predilection to infect critically ill, vulnerable patients. With its potential for rapid transmission, limited treatment options, and substantial mortality, CRAb is recognized as a critical, top-priority pathogen. Since its initial discovery in 1985, CRAb has disseminated globally, presenting a significant public health threat. CRAb is now endemic in many regions in Europe, South America, Asia, and Africa and globally contributes to over 50 000 deaths each year. Its ability to adhere to hospital surfaces, withstand desiccation, and form biofilms leads to widespread outbreaks. At-risk populations include those hospitalized and ventilated, and the most frequent presentations are respiratory and bloodstream infections. Carbapenem resistance in CRAb is primarily mediated by plasmid-borne carbapenemase genes, especially bla OXA-23. These genes, carried by several epidemic international clones, including IC1 and IC2, have facilitated the global dissemination of CRAb through horizontal gene transfer in healthcare settings. Mortality rates are >20% and vary substantially by region and by type of infection, with bloodstream infections carrying >40% mortality. Despite its significant impact, the development of treatments for CRAb remains inadequate. The novel agent sulbactam-durlobactam holds promise for improved patient outcomes, but ongoing therapeutic development, infection prevention, and antimicrobial stewardship are critical to combat this formidable pathogen. Here, we review the emergence and dissemination of CRAb, its molecular epidemiology and resistance mechanisms, summarize contemporary global clinical epidemiology and patient outcomes, and briefly describe existing and future therapeutics.

With limited treatments for carbapenem-resistant Klebsiella pneumoniae (CRKp), curtailing transmission is critical. We applied a network analysis using epidemiological admission data and bacterial genetics to characterize CRKp spread among patients in 16 acute care hospitals linked to 217 other healthcare facilities in the United States. Patients with diagnosed CRKp infection were selected from the Consortium on Resistance Against Carbapenems in Klebsiella and other Enterobacteriaceae (CRACKLE-1), a prospective, observational study conducted from 12/2011 to 6/2016. A network analysis was performed using epidemiological admission data and bacterial genetics to characterize putative CRKp transmission among patients across various healthcare facilities and the community. Overall, 347/526 patients (66%) had a putative transmission link to at least one other patient within the network. Most transmission chains were small (i.e., between 2 patients); however, the largest included 172 patients diagnosed over 1575 days. One-third of patients shared a genetically similar CRKp isolate with another patient but had no observed epidemiological linkages at any healthcare location. Patients with CRKp are part of extensive regional networks involving a large number of non-hospital healthcare settings such as skilled nursing facilities. Thus, controlling spread necessitates integrated surveillance and control initiatives at regional and national levels in addition to institution-specific approaches.

Genomic characteristics and optimal treatment of Corynebacterium jeikeium remain largely unknown. We collected clinical information and performed whole-genome sequencing analysis of the causative strains of six cases of C. jeikeium infection at a single hospital over a 9-year period. Additionally, whole-genome sequencing analysis was performed on 33 C. jeikeium strains from cases of bloodstream infection at eight hospitals. Antimicrobial susceptibility testing was performed, and the results were compared to the resistance genes identified. Publicly available genome data of strains of C. jeikeium complex, consisting of C. jeikeium sensu stricto, Corynebacterium macclintockiae, and Corynebacterium evansiae, worldwide, were combined with the data from this study to determine the distribution of genomic species. In the single-center study, cases of prosthetic osteoarticular infection, postoperative intra-abdominal infection, and catheter-related bloodstream infection were identified, and the causative strains were genomically identified as C. macclintockiae. All but one isolate (32/33, 97.0%) in the eight-center study identified as C. jeikeium by matrix-assisted laser desorption ionization-time of flight mass spectrometry were also genomically identified as C. macclintockiae. Nosocomial transmission was suggested in three strain pairs by core-genome single nucleotide polymorphism analysis. C. macclintockiae strains were generally multidrug-resistant, but all anti-methicillin-resistant Staphylococcus aureus agents, including teicoplanin, had favorable activity, and the strains without the tet(W) gene (22/38, 57.9%) were susceptible to tetracyclines. Genome analysis of 66 C. jeikeium complex strains collected worldwide, consisting mainly of clinical strains, re-identified 51 strains (77.3%) as C. macclintockiae. This study demonstrates that C. macclintockiae is the major genomic species of the C. jeikeium complex causing human infections.IMPORTANCERecent widespread use of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has facilitated the identification of Corynebacterium spp. in microbiology laboratories, thereby raising awareness of the clinical importance of these organisms. Nevertheless, the accumulation of information on genomic characteristics of Corynebacterium jeikeium has been significantly limited compared to other pathogenic organisms thus far. In this study, we analyzed causative strains of infections identified as C. jeikeium by MALDI-TOF MS, collected from multiple institutions throughout Japan, and found that most of these strains were genomically identified as Corynebacterium macclintockiae, a species that has been newly described recently. Collection of clinical information on selected cases showed that C. macclintockiae indeed caused invasive infections that required intravenous or long-term oral antimicrobial therapy. Additional analyses using genomic data of C. jeikeium complex strains registered in public databases suggest that C. macclintockiae is of global clinical importance.

INTRODUCTION: Personalized phage therapy is used in Europe and the United States to treat intractable infections caused by drug-resistant bacteria. This pilot study aimed to acquire feasibility data for clinical trials of individualized phage therapy in Japan. METHODS: An observational study was conducted from August 2023 to September 2024 in adults with drug-resistant bacterial infections and treatment failure or recurrence/relapse following antimicrobial therapy. Phages with activity against the detected bacteria were then identified from the environment and an existing phage library. RESULTS: Thirty patients with drug-resistant bacterial infections were enrolled. Of these, six (20 %) died within 30 days of detection. The most commonly detected bacteria were methicillin-resistant Staphylococcus aureus (MRSA) (n = 10, 33.3 %) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) (n = 5, 16.7 %). The most common nontuberculous mycobacterium (NTM) was Mycobacterium avium (n = 4, 13.3 %), followed by Mycobacterium abscessus (n = 2, 6.7 %). In terms of infection types, respiratory tract infections were the most common (n = 13, 43.3 %), followed by bone and joint infections (n = 6, 20 %) and skin and soft tissue infections (n = 6, 20 %). Phages with a titer of 108 PFU/ml or higher could be prepared for 26 out of 30 strains (86.7 %). Phages against CRPA were more readily identified from the environment than for MRSA and NTM. A phage against CRPA was purified to a lipopolysaccharide concentration of 0.023 EU/108 PFU. CONCLUSION: Personalized phages can be prepared for intractable infections caused by drug-resistant bacteria. These results support the conduct of clinical trials to implement personalized phage therapy in Japan.

The genus Aeromonas is increasingly implicated in human infections. However, accurate species-level identification remains challenging, particularly in clinical microbiology laboratories. This study aimed to develop a multiplex polymerase chain reaction (PCR) assay to identify four Aeromonas species-Aeromonas hydrophila, Aeromonas caviae, Aeromonas veronii, and Aeromonas dhakensis-most frequently associated with human infectious diseases. A total of 788 whole genome sequencing (WGS) data sets from 31 Aeromonas species were analyzed to identify open reading frames (ORFs) specifically present in A. hydrophila, A. caviae, A. veronii, and A. dhakensis. Primer sets were designed based on sequences of ORFs specific to each species to develop a multiplex PCR assay. To validate the efficacy of the assay, 256 clinical Aeromonas isolates were tested, and the results were compared with taxonomic affiliation inferred by WGS data, along with 19 type strains. The multiplex PCR successfully identified all strains of the four target species and produced no amplification in non-target species strains except the band for internal control. The multiplex PCR enables rapid and reliable identification of four Aeromonas spp. commonly involved in human infectious diseases.IMPORTANCEThe multiplex PCR assay facilitates accurate identification of clinically important Aeromonas spp. in clinical microbiology laboratories, providing crucial information to guide appropriate antimicrobial therapy and advance understanding of the epidemiology of Aeromonas spp.

Patients with hematologic diseases have experienced coronavirus disease 2019 (COVID-19) with a prolonged, progressive course. Here, we present clinical, pathological, and virological analyses of three cases of prolonged COVID-19 among patients undergoing treatment for B-cell lymphoma. These patients had all been treated with anti-CD20 antibody and bendamustine. Despite various antiviral treatments, high severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) levels persisted for >4 weeks, and two of them succumbed to COVID-19. The autopsy showed bronchopneumonia, interstitial pneumonia, alveolar hemorrhage, and fibrosis. Overlapping cytomegalovirus, fungal and/or bacterial infections were also confirmed. Sequencing of SARS-CoV-2 showed accumulation of mutations and changes in variant allele frequencies over time. NSP12 mutations V792I and M794I appeared independently in two cases as COVID-19 progressed. In vitro drug susceptibility analysis and an animal experiment using recombinant SARS-CoV-2 demonstrated that each mutation, V792 and M794I, was independently responsible for remdesivir resistance and attenuated pathogenicity. E340A, E340D, and F342INS mutations in the spike protein were found in one case, which may account for the sotrovimab resistance. Analysis of autopsy specimens indicated heterogeneous distribution of these mutations. In summary, we demonstrated temporal and spatial diversity in SARS-CoV-2 that evolved resistance to various antiviral agents in malignant lymphoma patients under immunodeficient conditions caused by certain types of immunochemotherapies. Strategies may be necessary to prevent the acquisition of drug resistance and improve outcomes, such as the selection of appropriate treatment strategies for lymphoma considering patients' immune status and the institution of early intensive antiviral therapy.

BACKGROUND AND OBJECTIVES: Carbapenem-resistant Gram-negative bacilli (CRGNB), especially Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii, are critical pathogens associated with excess morbidity and mortality. To elucidate their molecular epidemiology and clinical outcomes in Japan, patients with CRGNB were enrolled in the MDR organisms clinical research network (MDRnet) consisting of eight tertiary care facilities. METHODS: Between 2019 and 2022, 246 unique patients with carbapenem-resistant Enterobacterales (CRE), carbapenem-resistant P. aeruginosa (CRPA) and carbapenem-resistant A. baumannii (CRAB) isolates were prospectively enrolled. RESULTS: A total of 246 isolates were collected from 246 patients, including 78 (31.7%) CRE, 167 (67.9%) CRPA and 1 (0.4%) CRAB. For CRE, 74.4% of the isolates carried carbapenemase genes with predominance of bla IMP (64.1%). Only 2.4% of CRPA had carbapenemase genes, which was lower than CRE. Among the infected patients, 20.0% and 12.5% died of CRE and CRPA within 30 days, respectively. In patients with CRE, the mortality rate within 30 days for those without carbapenemase-producing Enterobacterales (CPE) was higher compared with those with CPE (22.2% compared with 18.8%). CONCLUSIONS: Our study highlights the unique molecular epidemiology and clinical outcomes of CRGNB in Japan.

Several Ephedra Herb-containing Kampo medicines are common initial treatments for various infections; however, the ephedrine alkaloids in Ephedra Herb can cause side effects by stimulating adrenergic receptors. Accordingly, an ephedrine alkaloids-free Ephedra Herb Extract (EFE) has been developed. This study aimed to evaluate whether EFE can be used effectively and safely in patients with mild coronavirus disease 2019 (COVID-19). We randomized patients with mild COVID-19 to receive EFE equivalent to 6 g of Ephedra Herb per day or a placebo for 14 days. The primary efficacy endpoint was the non-aggravation rate up to Day 15. We allocated 41 and 40 patients to the EFE and placebo groups, respectively. All participants were included in the mITT and safety analysis populations [male ratio, mean age: 31.7%, 42.0 years (EFE); 17.5%, 43.2 years (placebo)]. The non-aggravation rate up to Day 15 for the primary endpoint was 100.0% and 94.6% in the EFE and placebo group, respectively, with no between-group difference. The number of days to the improvement in nausea symptoms was significantly shorter in the EFE group. One patient in the placebo group discontinued the trial due to a side effect. Although EFE demonstrated safety in patients with mild COVID-19, it did not show superior efficacy compared to placebo for symptoms other than nausea.

BACKGROUND: With progressive accumulation of knowledge on SARS-CoV-2 infection clinical management, treatment guidelines recommended several options including remdesivir (RDV), a broad-spectrum antiviral. Given the evolving nature of COVID-19, capturing the totality of scientific evidence from clinical trials and observational studies is critical to inform clinical decision making. We conducted a systematic literature review (SLR) with meta-analysis (MA) to summarize RDV effectiveness among hospitalized adults. METHODS: We systematically searched MEDLINE, Embase and Cochrane Library databases for interventional and observational studies examining RDV efficacy. A rigorous double-reviewer approach was used for source identification, screening, data extraction and risk of bias assessment. A hierarchical random-effects model MA was used, with subgroup analyses for randomized controlled trials (RCT) and real-world (RW) studies. RESULTS: From January 2019 to December 2023 over 18,000 sources were screened and 122 unique studies were identified, reporting on 25,174 participants in RCTs and 1,279,859 in RW studies. Remdesivir significantly increased survival in the overall population [OR: 0.69 (0.55-0.86); p=0.001] across SARS-CoV-2 variants and disease severity levels: no supplemental oxygen [OR: 0.81 (0.75-0.88)], low-flow oxygen [OR: 0.71 (0.64-0.79)], high-flow oxygen [OR: 0.87 (0.83-0.91)] and invasive mechanical ventilation [OR: 0.78 (0.68-0.90)]. Rehospitalization risk was significantly reduced in patients receiving remdesivir [OR: 0.72 (0.64-0.81)]. CONCLUSION: Our comprehensive SLR, capturing the totality of evidence, showed a significant survival benefit among patients hospitalized for SARS-CoV-2 infection receiving RDV across all disease severity levels. To assure that healthcare providers are aware of and deploy evidence-based optimal care, recommendations should rely on both RCT and RW data.

We explored the role of commensal Neisseria in the emergence of third-generation cephalosporin-resistant N. meningitidis. Cefotaxime resistance-conferring penA795 was prevalent among commensal Neisseria isolates in Shanghai, China, and was acquired by a serogroup C quinolone-resistant sequence type 4821 N. meningitidis, Nm507, causing fulminant meningitis in an unvaccinated 2-year-old child.

BACKGROUND: Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) has been increasingly reported worldwide, posing a severe challenge to public health; however, the mechanisms driving its emergence and global dissemination remain unclear. METHODS: We analysed CR-hvKp strains derived from canonical hvKp backgrounds, and acquired a carbapenemase-encoding gene. These strains were identified from 485 CRKp isolates in the CRACKLE-2 China cohort, 259 CRKp isolates from a multi-centre study, and 67,631 K. pneumoniae genomes available in GenBank. Clinical isolates harbouring the IncFIIK34 KPC-2 plasmid were selected for genome sequencing, RNA-Seq, conjugation assays, in vivo, ex vivo, and in vitro phenotypic characterisation. FINDINGS: Analysis of clinical CR-hvKp isolates and the 414 genomes from 24 countries available in GenBank identified an IncFIIK34 KPC-2 plasmid as the prevalent KPC plasmid (detected in 25%, 45/178 of KPC-producing CR-hvKp). Compared with the epidemic IncFIIK2 KPC-2 plasmid, the IncFIIK34 KPC-2 plasmid exhibited a 100- to 1000-fold increase in conjugation frequency (10-4-10-5 vs. 10-7) and an in vitro growth advantage under meropenem challenge-likely due to the overexpression of conjugation-related genes and an increased blaKPC copy number and expression. CR-hvKp isolates and hvKp transconjugants carrying this plasmid often exhibited reduced mucoviscosity, while retaining hypervirulence in both murine models and human neutrophil assays. INTERPRETATION: The IncFIIK34 plasmid may be a key factor driving the global dissemination of CR-hvKp, underscoring the urgent need for enhanced molecular surveillance of this emerging pathogen. FUNDING: National Natural Science Foundation of China and National Institutes of Health.

BACKGROUND: The incidence of syphilis has been rising globally but effective screening strategies are lacking. Preoperative syphilis screening is commonly performed at Japanese hospitals for infection prevention purposes. However, its effectiveness in improving subsequent management is unclear. METHODS: A retrospective cohort study was conducted to assess the effectiveness of universal preoperative syphilis screening testing implemented at a Japanese tertiary care hospital from April 2017 to March 2023. The annual prevalence of positive preoperative treponemal tests was tracked, and subsequent clinical management for patients with a positive test result was investigated. Attributes of patients with a positive result who were more likely to receive further evaluation were also elucidated. RESULTS: In total, 82,439 patients underwent surgery during the study period. Preoperative treponemal testing was performed in 94.8% (78,170/82,439) of the patients. A positive test result was recorded in 544 (0.70%) with an annual positivity rate ranging from 0.61 to 0.83%, whereas the proportion of presumed active syphilis ranged from 0.02 to 0.08%. A total of 85 patients with a positive syphilis screening test, a nontreponemal test with a positive titer, and without history of syphilis were identified. Of those, only 45 patients (52.9%) received further evaluation. CONCLUSION: The positivity of preoperative treponemal testing was low despite the rising incidence of syphilis in Japan, and the prevalence of presumed active syphilis identified during the preoperative period was even smaller. Routine treponemal testing in the preoperative setting had limited utility in effectively identifying patients with active syphilis.

BACKGROUND: Serratia marcescens, an opportunistic nosocomial Gram-negative bacterium pathogen, has emerged as an important cause of healthcare-associated infections owing to its acquisition of antimicrobial resistance genes (ARGs) and virulence factor determinants. METHODS: Four carbapenem-resistant S. marcescens strains were recovered from patients admitted to different hospitals in 2017 and 2018. We assessed the antimicrobial resistance and virulence context, as well as the genetic similarities of four Brazilian S. marcescens strains, and compared the genomes of these S. marcescens isolates with whole genome data of 428 S. marcescens strains available in the NCBI Reference Sequence. Antimicrobial susceptibility testing was performed by disk diffusion and broth microdilution methods according to CLSI recommendations. Whole genome sequencing was performed using Illumina NextSeq 250-bp paired-end sequencing for two isolates, Sm424 and Sm613, which presented representative phenotypes. RESULTS: The pathogenicity of both sequenced strains was predicted using the Pathogen Finder tool. Both isolates carried efflux system genes (RND, SMR, MFS, ABC-family) and resistance genes (blaSTR-2, aac(6')-Ic, fos). Virulence factor genes involved in motility, regulation, capsule formation, acid resistance, and acriflavine resistance were also found. The Pathogen Finder tool predicted a >71% probability of being a human pathogen for Sm424 and Sm613. CONCLUSION: S. marcescens has shown increased adaptive, resistance, and pathogenic potential, being responsible for different nosocomial infections.

OBJECTIVES: Infections caused by carbapenemase-producing Gram-negative pathogens have become a significant global public health challenge due to limited treatment options. Pathogens producing metallo-β-lactamase are particularly problematic since they are not inhibited by conventional β-lactamase inhibitors. Herein, we assess the in vitro activity of aztreonam in combination with relebactam against a collection carbapenemase producing organisms, including strains producing both serine-β-lactamase and IMP-type metallo-β-lactamase that are commonly encountered in Japan. METHODS: A total of 119 carbapenemase-producing clinical isolates were used in this study. Minimum inhibitory concentrations (MICs) of aztreonam and imipenem alone and aztreonam/relebactam, aztreonam/avibactam and imipenem/relebactam combinations were determined by the broth microdilution method. RESULTS: Aztreonam MICs were reduced in combination with relebactam for strains producing ESBL or AmpC in addition to IMP-type, NDM-type, GES-type or OXA-48 carbapenemases and for Stenotrophomonas spp. Additionally, aztreonam/relebactam combination MICs were significantly lower than MICs of aztreonam alone among IMP producers, NDM producers and Stenotrophomonas spp. Significant differences between aztreonam/relebactam and aztreonam MICs were also observed for strains of E. coli, K. pneumoniae and Enterobacter spp., many of which produced both metallo-β-lactamase and serine-β-lactamase. The aztreonam/relebactam combination showed comparable to higher MICs compared with the aztreonam/avibactam combination. CONCLUSION: The addition of relebactam has a potential to restore the activity of aztreonam against strains that produce metallo-β-lactamase and serine-β-lactamase. The combination may have a role in the treatment of infections due to these strains in countries without access to ceftazidime-avibactam.

INTRODUCTION: Cases of hospital-onset bacteremia and fungemia (HOBF) are on the rise in Japanese hospitals, but little is known about their incidence in hospitals and how it relates to the availability of services provided by infectious diseases departments. METHODS: We herein investigated the monthly incidence density of HOBF per 1,000 patient days from 2013 through 2023 at a tertiary care hospital in Japan. The incidence of overall HOBF and pathogen-specific HOBF, including those caused by Enterobacterales, Staphylococcus aureus, coagulase-negative staphylococci (CNS), and Candida species, was tracked. Changes in the HOBF trend before and after the establishment of an infectious diseases department at the hospital were evaluated. RESULTS: In total, 4,315 HOBF-related events were identified. The overall incidence density of HOBF increased by 2.4-fold from 0.58 per 1,000 PD in 2013 to 1.42 per 1,000 PD in 2023. Both the level and trend changes in the incidence density of overall HOBF (+0.3142 for change in level [P < .001]; +0.0085 for change in trend [P < .001]), HOBF caused by S. aureus (+0.0983 for change in level [P < .001]; +0.0016 for change in trend [P = 0.016]), and Candida spp. (+0.0466 for change in level [P = 0.030]; +0.0019 for change in trend [P = 0.002]) significantly increased after the establishment of the infectious diseases department. CONCLUSION: The incidence density of overall HOBF and clinically important pathogen-specific HOBF increased over the last decade. The availability of services through the infectious diseases department was significantly associated with an increase in the HOBF incidence, likely suggesting improvement in the diagnosis of HOBF.

INTRODUCTION: Although skin and soft tissue infections (SSTIs) of the extremities are primarily caused by Gram-positive cocci (GPC), some cases are caused by Gram-negative rod (GNR). In addition, malignancy is a recognized risk factor for GNR infection. Nevertheless, information on the clinical and microbiologic characteristics of SSTIs of the extremities caused by GNR in patients with malignancy is limited. METHODS: Clinical and microbiological characteristics of patients with malignancy who developed bacteremic SSTIs of the extremities at a single cancer center over eight years were reviewed. In addition, whole-genome sequencing of the GNR isolates causing necrotizing fasciitis was conducted. RESULTS: Of 42 cases identified, 32 cases (76.2%) and 10 cases (23.8%) were caused by GPC and GNR, respectively. Four cases in the GNR group were due to Escherichia coli, and the remaining cases were caused by diverse species. The majority of cases in the GNR group were hospital-onset and the lesions were limited to a single extremity. Chronic liver disease, cellular immunodeficiency, or anatomic abnormalities of the gastrointestinal, biliary, or urinary tract underlay seven GNR cases (70%). Inappropriate empiric therapy was numerically more common in the GNR group compared to the GPC group (33.3% vs. 9.4%, p = 0.107). Whole-genome sequencing analysis revealed that two cases of GNR necrotizing fasciitis were caused by E. coli ST1193-fimH64 and Klebsiella pneumoniae K2-ST86. CONCLUSIONS: GNR organisms are a significant cause of SSTIs of the extremities in patients with malignancy and may be associated with inappropriate empiric therapy.

AmpC-mediated cephalosporin resistance occurs in 1.0% to 3.3% of Escherichia coli isolates due to production of either plasmid-mediated AmpC (p-AmpC) or chromosomal AmpC (c-AmpC). Data on the prevalence and molecular characteristics of AmpC-producing E. coli in pediatric patients are limited. We analyzed E. coli clinical strains with resistance phenotype consistent with AmpC production isolated from patients at a pediatric hospital in Japan between 2015 and 2022. Sequence types, resistance genes, and relevant mutations were identified through whole genome sequencing. Promoter and attenuator regions of the chromosomal ampC gene were examined and the presence of plasmid-mediated ampC genes was determined. Among 2,081 E. coli strains, 80 (3.8%) from 27 patients demonstrated the AmpC phenotype. The median patient age was 55 months, with 92.6% having underlying diseases, mainly renal and urinary tract abnormalities. Of the 27 strains, p-AmpC was found in 9 strains including 6 strains belonging to ST131, while c-AmpC was identified in 18 strains including 9 ST73 strains and 4 ST12 strains. ST131 and ST73 were the major AmpC-E. coli lineages isolated from children with underlying diseases. Most ST131 strains harbored p-ampC, while all ST73 strains acquired cephalosporin resistance by c-AmpC production through promoter and attenuator mutations, suggesting the presence of both AmpC mechanisms in a lineage-specific manner in E. coli identified among hospitalized children.

INTRODUCTION: The bacterium Corynebacterium urealyticum produces urease and can cause encrusted pyelitis, a condition characterized by calcifications of the renal pelvis and ureteral wall, which may obstruct the urinary tract. We describe a case of encrusted pyelitis caused by C. urealyticum in a kidney transplant patient presenting with altered consciousness due to hyperammonemia. CASE PRESENTATION: An 81-year-old woman with a history of cadaveric kidney transplantation, thirty years prior, presented with acute altered consciousness during hospitalization. Laboratory findings showed acute renal failure and hyperammonemia, and urinalysis revealed high pH (>9.0) and pyuria. Abdominal non-contrast computed tomography revealed calcification of the renal pelvis and hydronephrosis. C. urealyticum was isolated from both blood and urine cultures. A diagnosis of encrusted pyelitis and hyperammonemia caused by C. urealyticum was made, and intravenous vancomycin was administered. Following the initiation of vancomycin and the temporary hemodialysis, her hyperammonemia and altered consciousness rapidly improved. Treatment with vancomycin resulted in a reduction of the urinary tract encrustation. CONCLUSION: This case highlights C. urealyticum as a urinary pathogen that can lead to encrusted pyelitis, hyperammonemia, and altered consciousness in renal transplant patients.

Hypervirulent Klebsiella pneumoniae (hvKp) strains are considered to be relatively rare in the United States, but cases are increasingly reported. We prospectively and serially collected K. pneumoniae clinical isolates identified in respiratory specimens at a health system in Western Pennsylvania between 2020 and 2022. A total of 273 K. pneumoniae isolates from 216 unique patients were analyzed for markers of hypervirulence by both string test for a hypermucoid phenotype and multiplex PCR to detect isolates carrying cardinal virulence genes rmpA, rmpA2, iutA, and iro. Of the 273 isolates, 13 (4.8%) tested positive by string test including 11 nonduplicate K. pneumoniae isolates, and two of these (0.7%) were positive by PCR for virulence genes rmpA, rmpA2, iutA, and iro. The latter two putative hvKp strains, belonging to sequence types ST23-K1 and ST86-SLV-K2, possessed pLVPK-like plasmids, and were collected from community-associated infections in individuals without known travel histories. Both putative hvKp strains and two additional string test-positive strains were resistant to killing by human serum. The hvKp strains caused significant pneumonia in mice infected by oropharyngeal aspiration, with significantly higher weight loss and increased bacterial burden in the lungs of mice infected with the KL1 (ST23) strain compared to the KL2 (ST86-SLV) strain. We also observed decreased survival of mice infected with the KL1 strain compared to the KL2 strain. These findings add to the growing body of evidence suggesting that hvKp strains, once considered endemic to Asia, may now be circulating in North America.IMPORTANCECertain lineages of Klebsiella pneumoniae are increasingly recognized to cause severe community-associated infection, but information on their prevalence in the United States is limited. In a prospective, sequential cohort of 273 K. pneumoniae respiratory isolates, we identified two of them as genetically defined hypervirulent K. pneumoniae. The isolates were from local residents who developed community-onset pneumonia, suggesting that hypervirulent K. pneumoniae may already be present in the community.

The impact of treatment-emergent amino acid substitutions (TEAASs) in severe acute coronavirus 2 (SARS-CoV-2) 3C-like protease (3CLpro) on clinical and virologic outcomes was evaluated in patients with mild-to-moderate coronavirus disease 2019 (COVID-19) who received ensitrelvir 125 mg in the SCORPIO-SR trial. Individuals were randomised to ensitrelvir or matched placebo once daily for 5 days (first dose <72 h after disease onset). 3CLpro-TEAASs were identified by sequencing nsp5 encoding 3CLpro from pre- and post-treatment nasopharyngeal swabs. Time to resolution of a composite of five characteristic COVID-19 symptoms (TTR) was compared between patients with and without the most common 3CLpro-TEAASs in the ensitrelvir arm. The ensitrelvir and placebo intention-to-treat populations comprised 345 and 341 patients, respectively. 3CLpro-TEAASs were detected in 19/204 (9.3%) ensitrelvir-treated and 3/137 (2.2%) placebo-treated patients with paired sequence data. The most common 3CLpro-TEAASs in the ensitrelvir arm were M49L (n = 12), M49I (n = 3) and S144A (n = 2). In the placebo arm, all 3CLpro-TEAASs occurred in ≤1 patient. Median (95% confidence interval) TTR was comparable between patients with and without those TEAASs (158.8 h [112.1-281.9] vs 189.7 h [151.4-234.4]). Mean viral RNA levels declined more slowly in patients with M49L/I or S144A versus those without. Reductions in viral titre were unaffected by these TEAASs. The characteristics of recombinant SARS-CoV-2 with 3CLpro mutations were explored in vitro. Recombinant viruses with some 3CLpro mutations had reduced susceptibility to ensitrelvir in vitro, with limited effects on viral and competitive fitness. Continued surveillance is warranted to monitor the spread of viruses with 3CLpro mutations.

Bartonella henselae, a Gram-negative facultative intracellular bacterium, is the etiological agent of cat-scratch disease and also causes bacillary angiomatosis in immunocompromised individuals. Although the ability to promote vascular endothelial cell proliferation differs among Bartonella species, variations among strains within B. henselae remain unclear. Bartonella angiogenic factor A (BafA) and Bartonella adhesin A (BadA) have been identified as autotransporters of B. henselae that are involved in endothelial cell proliferation. Although strain-specific differences in the expression of BadA and the VirB/D4 type IV secretion system have been reported, BafA expression among B. henselae strains has yet to be examined. Therefore, the present study investigated the proliferation-promoting ability of 13 B. henselae strains from several sources in human umbilical vein endothelial cells (HUVECs). We identified BafA variants 1 and 2 based on the deduced amino acid sequences of its passenger domain. The recombinant proteins of both variants exhibited similar proliferation activity against HUVECs. However, BafA variant 2 strains showed cytotoxicity at a high bacterial inoculum in a direct coculture with HUVECs, which was attenuated in an indirect coculture. These strains, in contrast to BafA variant 1 strains, highly expressed BadA and exhibited bacterial aggregation. Based on a core genome SNP analysis of 50 B. henselae strains, the BafA variant types corresponded to clades 1-4. These results indicate that vasoproliferative traits differ among B. henselae clades based on the variant types. Therefore, this study provides a new conceptual framework in which the clades of B. henselae may predict their pathogenicity in humans.IMPORTANCEBartonella species including Bartonella henselae, Bartonella quintana, and Bartonella bacilliformis cause vasoproliferative lesions. Their proliferation-promoting ability in vascular endothelial cells differs among Bartonella species; however, it is unclear whether these differences exist among B. henselae strains. We herein showed that B. henselae strains exhibited variable proliferation-promoting ability and cytotoxicity in vascular endothelial cells, which corresponded to the bafA gene variants possessed by the strains. The expression levels of Bartonella angiogenic factor A (BafA) and Bartonella adhesin A, as well as the degree of proliferation-promoting ability and cytotoxicity in endothelial cells, varied among the strains. A core genome SNP analysis of strains using whole genome sequencing data divided B. henselae strains into four clades, with each clade corresponding to BafA variants 1-4. These results suggest the differential vasoproliferative potency of B. henselae, with potential implications in clinical management, including risk stratification and predictions of the clinical course.

Carbapenem-resistant Acinetobacter baumannii has been associated with over three hundred thousand annual deaths globally. It is resistant to most available antibiotics and associated with high morbidity and mortality. No global consensus currently exists for treatment strategies that balance safety and efficacy because of heterogeneity of treatment regimens in current clinical practice and scarcity of large-scale controlled studies arising from difficulties in establishing robust clinical outcomes. This review outlines the epidemiology and resistance mechanisms of carbapenem-resistant A. baumannii, then summarizes available clinical data on each approved agent with activity against this pathogen. Emerging treatment options such as cefiderocol and sulbactam-durlobactam show promise, but their success hinges on comprehensive clinical validation and access in regions most impacted by this pathogen. New therapeutic modalities that are in various stages of clinical development are also discussed.

A 70-year-old Japanese man with well-controlled diabetes mellitus and chronic kidney disease was hospitalized for an examination of acute renal failure and elevated inflammatory reactions. He had a history of Klebsiella pneumoniae bacteremia without extended-spectrum β-lactamase (ESBL) production five months earlier. The patient was found to have bacteremia due to hypermucoviscous ESBL-producing Klebsiella pneumoniae, and developed septic shock, multiple cerebral infarctions, and an abscess in the left masticatory muscle space. The causative organism was resistant to ampicillin-sulbactam and piperacillin-tazobactam, which were used for empiric therapy, and the patient died despite subsequent definitive treatment with meropenem. Whole genome sequencing analysis showed that the strain of K. pneumoniae was ST412 with capsular genotype K57 and carried virulence genes iroBCDN, iucABCD, iutA, mrkABCDFHIJ, rmpA2, ybtAEPQSTUX. The strain also carried the blaCTX-M-15 ESBL gene. Although the antimicrobial susceptibility of the causative organisms of hvKp infections in Japan has been favorable in most cases, severe infections caused by ESBL-producing hvKp may increase in the near future considering the recent increase in ESBL-producing K. pneumoniae.

BACKGROUND: Despite the global public health threat posed by carbapenem-resistant Enterobacter spp., clinical and molecular epidemiological studies on international isolates remain scarce. Historically, the taxonomy of Enterobacter has been challenging, limiting our understanding of the clinical characteristics and outcomes of carbapenemase-producing Enterobacter spp. infections. METHODS: Hospitalized patients enrolled in the CRACKLE-2 study (ClinicalTrials.gov, NCT03646227) from 2016-2018 with cultures positive for carbapenemase-producing Enterobacter spp. were included. Clinical and microbiologic data were collected from health records. Whole genome sequencing was performed, and the population structures of selected predominant clones were analyzed. RESULTS: We enrolled 136 hospitalized patients with carbapenemase-producing Enterobacter spp. from 30 hospitals in 7 countries. Among the 136 isolates, eleven Enterobacter species were identified, with most isolates belonging to E. xiangfangensis (n=81, 60%) and E. hoffmannii (n=17, 13%), and carrying blaKPC (n=106, 78%) and blaNDM (n=12, 9%). Clinical characteristics and outcomes were similar among patients with E. xiangfangensis, E. hoffmannii or the other Enterobacter spp. 30-day mortality was 20% and older age at enrollment (adjusted odds ratio 1.42, 95% confidence interval 1.08-1.87) was associated with increased mortality. Sequence type (ST)171 E. xiangfangensis, ST78 E. hoffmannii, and ST93 E. xiangfangensis were the predominant clones, and the acquisition of fluoroquinolone resistance-associated mutations and carbapenemase-encoding plasmids contributed to their formation and global dissemination. CONCLUSIONS: Our findings demonstrated that E. xiangfangensis and E. hoffmannii are common species among international carbapenemase-producing Enterobacter spp., potentially linked to the clonal spread of a few predominant clones that have acquired fluoroquinolone resistance and carbapenemase-encoding plasmids.

INTRODUCTION: Escherichia coli ST1193 is an emerging high-risk clone associated with the production of plasmid-mediated CTX-type extended-spectrum β-lactamases. However, this clone has seldom been found to contain plasmids carrying carbapenemase genes. We report two epidemiologically unlinked multidrug-resistant (MDR) clinical isolates of E. coli ST1193 with plasmids harbouring NDM-type carbapenemase genes from the Gulf region. METHODS: The isolates were identified by MALDI-TOF MS and antibiotic susceptibility testing was performed using the VITEK 2/Phoenix system. A conjugation experiment was performed to assess the transferability of the resistance plasmids. Genomic DNA of both isolates was subject to Illumina sequencing; one isolate was also sequenced using Oxford Nanopore technology. Bioinformatics analyses were performed to detect antimicrobial resistance genes, and to annotate the genetic context of the NDM genes. RESULTS AND CONCLUSIONS: Both isolates were resistant to carbapenems using phenotypic tests. Conjugation experiment confirmed that NDM-5-encoding plasmids of both strains could be transferred to the recipient cells. The completed NDM-5-encoding plasmid of E. coli isolate FQ71 was highly similar to several plasmids from ST410 isolates in the NCBI database. Genomic analysis revealed the presence of transposase genes and transposons in the flanking regions of the NDM genes in the plasmids. Since carbapenems constitute first-line agents for the treatment of serious infections caused by ESBL producers, E. coli ST1193 isolates co-producing ESBL and NDM-type carbapenemases represent a serious challenge for antimicrobial stewardship and infection control programmes.

Antibiotic resistance is one of the most pressing threats to human health, yet recent work highlights how loss of resistance may also drive pathogenesis in some bacteria. In two recent studies, we found that β-lactam antibiotic and nutrient stresses faced during infection selected for the genetic inactivation of the Pseudomonas aeruginosa (Pa) antibiotic efflux pump mexEFoprN. Unexpectedly, efflux pump mutations increased Pa virulence during infection; however, neither the prevalence of efflux pump inactivating mutations in real human infections, nor the mechanisms driving increased virulence of efflux pump mutants are known. We hypothesized that human infection would select for efflux pump mutations that drive increased virulence in Pa clinical isolates. Using genome sequencing of hundreds of Pa clinical isolates, we show that mexEFoprN efflux pump inactivating mutations are enriched in Pa cystic fibrosis isolates relative to Pa intensive care unit clinical isolates. Combining RNA-seq, metabolomics, genetic approaches, and infection models we show that efflux pump mutants have elevated expression of two key Pa virulence factors, elastase and rhamnolipids, which increased Pa virulence and lung damage during both acute and chronic infections. Increased virulence factor production was driven by higher Pseudomonas quinolone signal levels in the efflux pump mutants. Finally, genetic restoration of the efflux pump in a representative ICU clinical isolate and the notorious CF Pa Liverpool epidemic strain reduced their virulence. Together, our findings suggest that mutations inactivating antibiotic resistance mechanisms could lead to greater patient mortality and morbidity.

OBJECTIVES: Consultation with infectious disease specialists is associated with reduced patient mortality in the care of patients with Staphylococcus aureus bacteremia (SAB) through appropriate management of complications including infective endocarditis. This study aimed to determine the rates of confirmation of a negative blood culture, implementation of echocardiography, and administration of appropriate antibiotics in patients with SAB at a university hospital in Japan that provides general internal medicine and not an infectious disease consultation service. METHODS: We conducted a retrospective cohort study at Dokkyo Medical University Hospital in Japan. Patients eligible for inclusion in the study were ≥20 years of age with ≥1 positive blood culture for S. aureus identified in a clinical microbiology laboratory. The primary outcome was the proportion of patients with confirmation of a negative blood culture, implementation of echocardiography, and administration of appropriate antimicrobial agents. RESULTS: A total of 109 patients with SAB were included in the analysis. Follow-up blood cultures were collected in 91 patients and negative results were documented in 88 patients. Follow-up blood culture collection was performed within 4 days of the initial blood culture collection in 49 patients. Echocardiography was performed appropriately in 40 patients. Appropriate antibiotic therapy was administered in 36 patients. CONCLUSIONS: Quality-of-care indicators were more commonly implemented in patients with SAB who received general internal medicine consultation than in those who did not.

BACKGROUND: COVID-19 remains a major public health concern, with continued resurgences of cases and substantial risk of mortality for hospitalized patients. Remdesivir has become standard-of-care for hospitalized COVID-19 patients. Given the continued evolution of the disease, clinical management relies on evidence from the current endemic period. METHODS: Using the PINC AI Healthcare database, effectiveness of remdesivir was evaluated among adults hospitalized with a primary diagnosis of COVID-19 between December 2021 and February 2024. Three cohorts were analysed: adults, elderly (≥65 years), and those with documented COVID-19 pneumonia. Analyses were stratified by oxygen requirements. Patients receiving remdesivir were matched to those not receiving remdesivir using propensity score matching. Cox proportional hazards models were used to examine in-hospital mortality. RESULTS: 169,965 adults hospitalized for COVID-19 were included, of which 94,129 (55.4%) initiated remdesivir in the first two days of hospitalization. Remdesivir was associated with a significantly lower mortality rate as compared to no remdesivir among patients with no supplemental oxygen charges (NSOc) (aHR [95% CI]: 14-day, 0.75 [0.69-0.82]; 28-day, 0.77 [0.72-0.83]) and among those with supplemental oxygen charges (SOc): 14-day, 0.76 [0.72-0.81]; 28-day, 0.79 [0.74-0.83]) (p<0.0001, for all). Similar findings were observed for elderly patients and those hospitalized with COVID-19 pneumonia. CONCLUSIONS: This evidence builds on learnings from randomized controlled trials from the pandemic era to inform clinical practices. Remdesivir was associated with significant reduction in mortality for hospitalized patients including the elderly and those with COVID-19 pneumonia.

UNLABELLED: Diffuse panbronchiolitis (DPB) is a rare, idiopathic inflammatory disease primarily diagnosed in East Asian populations. DPB is characterized by diffuse pulmonary lesions, inflammation of the respiratory bronchioles, and bacterial infections of the airway. Historically, sputum cultures reveal Pseudomonas aeruginosa in 22% of DPB patients, increasing to 60% after 4 years from disease onset. Although DPB patients have a known susceptibility to respiratory P. aeruginosa infections, as is observed in other chronic lung diseases such as cystic fibrosis (CF), the characterization of DPB P. aeruginosa strains is limited. In this study, we characterized 24 strains obtained from a cohort of DPB patients for traits previously associated with virulence, including growth, motility, antibiotic susceptibility, lipopolysaccharide structure, and genomic diversity. Our cohort of DPB P. aeruginosa strains exhibits considerable genomic variability when compared with isolates from people with cystic fibrosis chronically colonized with P. aeruginosa and acute P. aeruginosa infection isolates. Similar to CF, DPB P. aeruginosa strains produce a diverse array of modified lipid A structures. Antibiotic susceptibility testing revealed increased resistance to erythromycin, a representative agent of the macrolide antibiotics used to manage DPB patients. Differences in the O-antigen type among P. aeruginosa strains collected from these different backgrounds were also observed. Ultimately, the characterization of DPB P. aeruginosa strains highlights several unique qualities of P. aeruginosa strains collected from chronically diseased airways, underscoring the challenges in treating DPB, CF, and other obstructive respiratory disease patients with P. aeruginosa infections. IMPORTANCE: Diffuse panbronchiolitis (DPB), a chronic lung disease characterized by persistent P. aeruginosa infection, serves as an informative comparator to more common chronic lung diseases, such as cystic fibrosis (CF). This study aimed to better address the interplay between P. aeruginosa and chronically compromised airway environments through the examination of DPB P. aeruginosa strains, as existing literature regarding DPB is limited to case reports, case series, and clinical treatment guidelines. The evaluation of these features in the context of DPB, in tandem with prevailing knowledge of P. aeruginosa strains collected from more common chronic lung diseases (e.g., CF), can aid in the development of more effective strategies to combat respiratory P. aeruginosa infections in patients with chronic lung diseases.

BACKGROUND: Cefiderocol exhibits potent in vitro activity against carbapenem-resistant Acinetobacter baumannii (CRAb), but this activity has not consistently translated to improved outcomes among patients. Cefiderocol heteroresistance, or the presence of a resistant subpopulation, has been proposed as one possible explanation. The objective of this study was to explore associations between heteroresistance and outcomes of patients with CRAb infections. METHODS: Baseline CRAb isolates were collected from 27 consecutive patients in the USA and Italy. Cefiderocol susceptibility was tested by broth microdilutions in triplicate. Heteroresistance was defined by population analysis profiling in duplicate. Resistance mechanisms and strain relatedness were evaluated through comparative genomic analysis. RESULTS: Overall, 59% of infecting CRAb isolates were identified as cefiderocol-heteroresistant; rates were higher among isolates from Italy (79%) than the USA (38%). The median Charlson Comorbidity and SOFA scores were 4 and 5, respectively; 44% of patients had pneumonia, which was the most common infection type. Rates of 28-day clinical success and survival were 30% and 73%, respectively. By broth microdilution, cefiderocol MICs ≥1 mg/L were associated with higher failure rates than MICs ≤0.5 mg/L (81% versus 55%). Rates of clinical failure were numerically higher among patients infected by cefiderocol-heteroresistant compared with susceptible CRAb (81% versus 55%). Whole-genome sequencing identified a premature stop codon in the TonB-dependent receptor gene piuA in six isolates, all of which were heteroresistant. CONCLUSIONS: This pilot study supports the hypothesis that cefiderocol treatment failure may be associated with higher MICs and/or the presence of heteroresistance. Further studies are needed to confirm these findings.

INTRODUCTION: Since the original COVID-19 vaccines were developed, abundant clinical trial and real-world evidence evaluating the efficacy, effectiveness, and safety of COVID-19 vaccines has been collected. Knowledge of the relative benefits and risks of COVID-19 vaccines is essential for building trust within target populations, ensuring they remain effectively and safely protected against an enduring infectious threat. AREAS COVERED: This descriptive review discusses the benefits and risks associated with marketed Moderna, Inc. mRNA-based COVID-19 vaccines, focusing on their real-world effectiveness and safety profiles in various age groups. Adverse events of interest and potential benefits of vaccination are reviewed, including reduced risk for severe COVID-19 and long-term health outcomes, reduced economic and societal costs, and reduced risk for SARS-CoV-2 transmission. EXPERT OPINION: Post-marketing safety and real-world data for Moderna, Inc. COVID-19 mRNA vaccines strongly support a positive benefit - risk profile favoring vaccination across all age groups. Although COVID-19 is no longer considered a global health pandemic, health risks associated with SARS-CoV-2 infection remain high. Concerted efforts are required to engage communities and maintain protection through vaccination. Continued surveillance of emerging variants and monitoring of vaccine safety and effectiveness are crucial for ensuring sustained protection against SARS-CoV-2.

BACKGROUND: The CDC reported a 35% increase in hospital-onset (HO) carbapenem-resistant Enterobacterales (CRE) infections during the COVID-19 pandemic. We evaluated patient outcomes following HO and community-onset (CO) CRE bloodstream infections (BSI). METHODS: Patients prospectively enrolled in CRACKLE-2 from 56 hospitals in 10 countries between 30 April 2016 and 30 November 2019 with a CRE BSI were eligible. Infections were defined as CO or HO by CDC guidelines, and clinical characteristics and outcomes were compared. The primary outcome was desirability of outcome ranking (DOOR) 30 days after index culture. Difference in 30-day mortality was calculated with 95% CI. RESULTS: Among 891 patients with CRE BSI, 65% were HO (582/891). Compared to those with CO CRE, patients with HO CRE were younger [median 60 (Q1 42, Q3 70) years versus 65 (52, 74); P < 0.001], had fewer comorbidities [median Charlson comorbidity index 2 (1, 4) versus 3 (1, 5); P = 0.002] and were more acutely ill (Pitt bacteraemia score ≥4: 47% versus 32%; P < 0.001). The probability of a better DOOR outcome in a randomly selected patient with CO BSI compared to a patient with HO BSI was 60.6% (95% CI: 56.8%-64.3%). Mortality at 30-days was 12% higher in HO BSI (192/582; 33%) than CO BSI [66/309 (21%); P < 0.001]. CONCLUSION: We found a disproportionately greater impact on patient outcomes with HO compared to CO CRE BSIs; thus, the recently reported increases in HO CRE infections by CDC requires rigorous surveillance and infection prevention methods to prevent added mortality.

Klebsiella pneumoniae is a Gram-negative bacterium that causes both community- and healthcare-associated infections. Although various virulence factors and highly pathogenic phenotypes have been reported, the pathogenicity of K. pneumoniae is still not fully understood. In this study, we utilized whole-genome sequencing data of 168 clinical K. pneumoniae strains to assess pathogenicity. This work was based on the concept that the genetic composition of individual genomes (referred to as holistic gene content) of the strains may contribute to their pathogenicity. Holistic gene content analysis revealed two distinct groups of K. pneumoniae strains ('major group' and 'minor group'). The minor group included strains with known highly pathogenic clones (ST23, ST375, ST65 and ST86). The minor group had higher rates of capsular genotype K1 and presence of nine specific virulence genes (rmpA, iucA, iutA, irp2, fyuA, ybtS, iroN, allS and clbA) compared to the major group. Pathogenicity was assessed using Galleria mellonella larvae. Infection experiments revealed lower survival rates of larvae infected with strains from the minor group, indicating higher virulence. In addition, the minor group had a higher string test positivity rate than the major group. Holistic gene content analysis predicted possession of virulence genes, string test positivity and pathogenicity as observed in the G. mellonella infection model. Moreover, the findings suggested the presence of as yet unrecognized genomic elements that are either involved in the acquisition of virulence genes or associated with pathogenicity.

Escherichia coli multi-locus sequence type ST131 is a globally distributed pandemic lineage that causes multidrug-resistant extra-intestinal infections. ST131 E. coli frequently produce extended-spectrum β-lactamases (ESBLs), which confer resistance to many β-lactam antibiotics and make infections difficult to treat. We sequenced the genomes of 154 ESBL-producing E. coli clinical isolates belonging to the ST131 lineage from patients at the University of Pittsburgh Medical Center (UPMC) between 2004 and 2018. Isolates belonged to the well described ST131 clades A (8%), B (3%), and C (89%). Time-dated phylogenetic analysis estimated that the most recent common ancestor (MRCA) for all clade C isolates emerged around 1989, consistent with previous studies. We identified multiple genes potentially under selection in clade C, including the cell wall assembly gene ftsI, the LPS biosynthesis gene arnC, and the yersiniabactin uptake receptor fyuA. Diverse ESBL-encoding genes belonging to the blaCTX-M, blaSHV, and blaTEM families were identified; these genes were found at varying numbers of loci and in variable numbers of copies across isolates. Analysis of ESBL flanking regions revealed diverse mobile elements that varied by ESBL type. Overall, our findings show that ST131 subclade C dominated among patients and uncover possible signals of ongoing adaptation within this ST131 lineage.

BACKGROUND: Use of anti-carbapenem-resistant Enterobacterales (anti-CRE) agents such as ceftazidime/avibactam has been associated with improved clinical outcome in cohorts that primarily include patients infected with CRE that are resistant to meropenem (MCRE). OBJECTIVES: To clarify whether patients with CRE resistant to ertapenem but susceptible to meropenem (ertapenem-only-resistant Enterobacterales; EORE) benefit from therapy with anti-CRE agents. METHODS: Patients treated for CRE infection in hospitals in the USA between 2016 and 2019 and enrolled in the CRACKLE-2 study were included. The primary outcome was the desirability of outcome ranking (DOOR) assessed at 30 days after index cultures. RESULTS: The EORE group included 213 patients and the MCRE group included 643. The demographics were similar between the groups except for the patients' race and origin before admission. The MCRE group received anti-CRE agents for definitive therapy significantly more frequently compared with the EORE group (30% versus 5% for ceftazidime/avibactam). We did not observe a significant difference between the groups in the adjusted DOOR probability of a more desirable outcome for a randomly selected patient in the EORE group compared with the MCRE group (52.5%; 95% CI, 48.3%-56.7%). The MCRE group had a similar proportion of patients who died at 30 days (26% versus 21%) and who were discharged to home (29% versus 40%), compared with the EORE group. CONCLUSIONS: Patients with clinical EORE infection rarely received anti-CRE agents, but attained similar outcomes compared with patients with MCRE infection. The findings support current IDSA treatment guidance for meropenem- or imipenem-based therapy for treatment of EORE infections.

Modification of the R1 and R2 side chain structures has been used as the main strategy to expand the spectrum of cephalosporins and impart resistance to hydrolysis by β-lactamases. These structural modifications also result in a wide range of plasma protein binding, especially with human serum albumin (HSA). Here, we determined the crystal structures of the HSA complexes with two clinically important cephalosporins, ceftriaxone and cefazolin, and evaluated the binding of cephalosporin to HSA by susceptibility testing and competitive binding assay. Ceftriaxone and cefazolin bind to subdomain IB of HSA, and their cephem core structures are recognized by Arg117 of HSA. Tyr161 of HSA changes its rotamer depending on the cephalosporin, resulting in alterations of the cavity shape occupied by the R2 side chain of cephalosporins. These findings provide structural insight into the mechanisms underlying the HSA binding of cephalosporins.

BACKGROUND: Klebsiella pneumoniae carbapenemase-producing K pneumoniae (KPC-Kp) bloodstream infections are associated with high mortality. We studied clinical bloodstream KPC-Kp isolates to investigate mechanisms of resistance to complement, a key host defense against bloodstream infection. METHODS: We tested growth of KPC-Kp isolates in human serum. In serial isolates from a single patient, we performed whole genome sequencing and tested for complement resistance and binding by mixing study, direct enzyme-linked immunosorbent assay, flow cytometry, and electron microscopy. We utilized an isogenic deletion mutant in phagocytosis assays and an acute lung infection model. RESULTS: We found serum resistance in 16 of 59 (27%) KPC-Kp clinical bloodstream isolates. In 5 genetically related bloodstream isolates from a single patient, we noted a loss-of-function mutation in the capsule biosynthesis gene, wcaJ. Disruption of wcaJ was associated with decreased polysaccharide capsule, resistance to complement-mediated killing, and surprisingly, increased binding of complement proteins. Furthermore, an isogenic wcaJ deletion mutant exhibited increased opsonophagocytosis in vitro and impaired in vivo control in the lung after airspace macrophage depletion in mice. CONCLUSIONS: Loss of function in wcaJ led to increased complement resistance, complement binding, and opsonophagocytosis, which may promote KPC-Kp persistence by enabling coexistence of increased bloodstream fitness and reduced tissue virulence.

This exploratory analysis of the double-blind, phase 3, SCORPIO-SR trial assessed the effect of ensitrelvir in preventing post coronavirus disease 2019 (COVID-19) condition (PCC). Patients with mild-to-moderate COVID-19 were randomized (1:1:1) within 120 h of symptom onset; received 5-day oral ensitrelvir 125 mg (375 mg on day 1), 250 mg (750 mg on day 1), or a matching placebo once daily; and were assessed for the severity of typical PCC symptoms using a self-administered questionnaire. In total, 341, 317, and 333 patients were assessed in the ensitrelvir 125-mg, ensitrelvir 250-mg, and placebo groups, respectively (mean age, 35.6-36.5 years; men, 53.3%-58.3%). On days 85, 169, and 337, ensitrelvir 125-mg treatment showed 32.7% (95% confidence interval [CI]: 30.6, 66.1), 21.5% (95% CI: 37.3, 55.6), and 24.6% (95% CI: 43.7, 60.9) reductions versus placebo, respectively, in the risk of any of the 14 acute-phase COVID-19 symptoms (at least one mild, moderate, or severe symptom with general health not returning to the usual level). Ensitrelvir 250-mg treatment showed 10.9% (95% CI: 67.0, 52.8), 9.5% (95% CI: 56.6, 48.0), and 30.6% (95% CI: 36.2, 65.5) risk reductions versus placebo on days 85, 169, and 337, respectively. Risk reductions were observed in any of the 4 neurological symptoms and were more pronounced among patients with high acute-phase symptom scores at baseline and among those with a baseline body mass index ≥25 kg/m2. Ensitrelvir treatment in the acute phase of COVID-19 may reduce the risk of various symptoms associated with PCC. TRIAL REGISTRATION NUMBER: jRCT2031210350.

BACKGROUND: Stenotrophomonas maltophilia is a carbapenem-resistant Gram-negative pathogen increasingly responsible for difficult-to-treat nosocomial infections. OBJECTIVES: To describe the contemporary clinical characteristics and genome epidemiology of patients colonized or infected by S. maltophilia in a multicentre, prospective cohort. METHODS: All patients with a clinical culture growing S. maltophilia were enrolled at six tertiary hospitals across Japan between April 2019 and March 2022. The clinical characteristics, outcomes, antimicrobial susceptibility and genomic epidemiology of cases with S. maltophilia were investigated. RESULTS: In total, 78 patients were included representing 34 infection and 44 colonization cases. The median age was 72.5 years (IQR, 61-78), and males accounted for 53 cases (68%). The most common comorbidity was localized solid malignancy (39%). Nearly half of the patients (44%) were immunosuppressed, with antineoplastic chemotherapy accounting for 31%. The respiratory tract was the most common site of colonization (86%), whereas bacteraemia accounted for most infection cases (56%). The 30 day all-cause mortality rate was 21%, which was significantly higher in infection cases than colonization cases (35% versus 9%; adjusted HR, 3.81; 95% CI, 1.22-11.96). Susceptibility rates to ceftazidime, levofloxacin, minocycline and sulfamethoxazole/trimethoprim were 14%, 65%, 87% and 100%, respectively. The percentage of infection ranged from 13% in the unclassified group to 86% in genomic group 6A. The percentage of non-susceptibility to ceftazidime ranged from 33% in genomic group C to 100% in genomic groups 6 and 7 and genomic group geniculate. CONCLUSIONS: In this contemporary multicentre cohort, S. maltophilia primarily colonized the respiratory tract, whereas patients with bacteraemia had the highest the mortality from this pathogen. Sulfamethoxazole/trimethoprim remained consistently active, but susceptibility to levofloxacin was relatively low. The proportions of cases representing infection and susceptibility to ceftazidime differed significantly based on genomic groups.

BACKGROUND: This phase 2b/3, randomized, placebo-controlled trial explored the efficacy and evaluated the safety of ensitrelvir. This trial involved individuals with asymptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and patients with mild symptoms of coronavirus disease 2019 (COVID-19). METHODS: The trial was conducted at 57 medical institutions in Japan, South Korea, and Vietnam (study period: January 6-August 14, 2022). Eligible participants were randomized (1:1:1) to the ensitrelvir 125-mg, ensitrelvir 250-mg, or placebo group, received the allocated intervention orally, and were followed up until Day 28. Participants self-rated the severity of 14 typical COVID-19 symptoms and recorded the data in an electronic diary. RESULTS: In total, 572 participants (194, 189, and 189 in the ensitrelvir 125-mg, ensitrelvir 250-mg, and placebo groups, respectively) were included in the intention-to-treat population. Ensitrelvir 125-mg group observed a 77% reduction in the risk of developing any of the 14 COVID-19 symptoms or fever and a 29% reduction in the risk of worsening of such symptoms or fever versus placebo (statistically nonsignificant). The viral RNA, viral titer, and time to infectious viral clearance observed a statistically significant decrease versus placebo. Most treatment-related adverse events (TEAEs) were mild to moderate in severity, and the most common TEAE observed across groups was a decrease in high-density lipoprotein. CONCLUSIONS: Our exploratory results suggest a potential reduction in the risk of development or worsening of COVID-19 symptoms with ensitrelvir. Ensitrelvir showed antiviral efficacy and was well tolerated. TRIAL REGISTRATION: Japan Registry of Clinical Trials identifier: jRCT2031210350.

Carbapenemase-producing Enterobacterales (CPEs) are one of the top priority antimicrobial-resistant pathogens. Among CPEs, those producing acquired metallo-β-lactamases (MBLs) are considered particularly problematic as few agents are active against them. Imipenemase (IMP) is the most frequently encountered acquired MBL in Japan, but comprehensive assessment of clinical and microbiological features of IMP-producing Enterobacterales infection remains scarce. Here, we retrospectively evaluated 62 patients who were hospitalized at a university hospital in Japan and had IMP-producing Enterobacterales from a clinical culture. The isolates were either Enterobacter cloacae complex or Klebsiella pneumoniae, and most of them were isolated from sputum. The majority of K. pneumoniae, but not E. cloacae complex isolates, were susceptible to aztreonam. Sequence type (ST) 78 and ST517 were prevalent for E. cloacae complex and K. pneumoniae, respectively, and all isolates carried blaIMP-1. Twenty-four of the patients were deemed infected with IMP-producing Enterobacterales. Among the infected patients, therapy varied and largely consisted of conventional β-lactam agents, fluoroquinolones, or combinations. Three (13%), five (21%), and nine (38%) of them died by days 14, 30, and 90, respectively. While incremental mortality over 90 days was observed in association with underlying comorbidities, active conventional treatment options were available for most patients with IMP-producing Enterobacterales infections, distinguishing them from more multidrug-resistant CPE infections associated with globally common MBLs, such as New Delhi metallo-β-lactamase (NDM) and Verona integron-encoded metallo-β-lactamase (VIM).