Yersinia enterocolitica infection-induced liver abscess is extremely rare in clinical practice. It is usually only seen in specific high-risk groups, such as those with iron overload (such as hemochromatosis patients), immunosuppression (such as those undergoing chemotherapy, organ transplantation, or HIV infection), and those with poorly controlled diabetes. This case report presents a rare case of liver abscess complicated with sepsis caused by Yersinia enterocolitica. The pathogen was precisely identified through targeted next-generation sequencing of liver abscess fluid, combined with blood culture and abscess fluid culture, all of which consistently confirmed Yersinia enterocolitica. The treatment involved a comprehensive approach of percutaneous liver puncture and drainage combined with sensitive antibiotics, supplemented by dynamic imaging follow-up to monitor lesion changes. Eventually, the patient's condition significantly improved and they recovered.

Pseudomonas otitidis harbors an intrinsic subclass B3 metallo-β-lactamase (MBL), named POM, which contributes to reduced susceptibility to carbapenems. However, the diversity and functional implications of POM variants remain poorly studied. In this study, we investigated POM MBL in 65 strains from clinical, animal, and environmental origins from several countries, of which 19 Brazilian environmental strains were subjected to antimicrobial susceptibility testing. Sequence analysis identified the previously described POM-1 and POM-2, as well as 24 novel variants (POM-4 to POM-27). All variants displayed high amino acid identity (≥ 98.25%) and conserved key residues involved in zinc binding, indicating strong structural conservation. Whole-genome single nucleotide polymorphism analysis of P. otitidis genomes indicated that the distribution of POM variants was partly structured by strain phylogeny. Phenotypic comparisons were restricted to the 19 Brazilian environmental isolates and were descriptive only. These strains showed consistently elevated carbapenem minimum inhibitory concentrations (MIC), with meropenem and imipenem values ranging from 8 to 64 mg/L and 4 to 64 mg/L, respectively. Carbapenem MIC distributions overlapped across POM variants, with no clear genotype-phenotype pattern observed within this collection. Susceptibility to other antimicrobial classes was variable, although non-β-lactam agents generally retained activity. These findings demonstrate that POM enzymes constitute a highly conserved family of intrinsic MBL enzymes, while the relationship between POM sequence variation and carbapenem susceptibility remains unresolved within the limited phenotypic dataset. While variant-level identification has limited clinical utility, characterization of POM diversity provides insights into the evolution of intrinsic resistance.

Overdiagnosis and overtreatment of urinary tract infections (UTIs) and asymptomatic bacteriuria (AB) increase antimicrobial resistance. The aim of this study was to evaluate resistance patterns and antibiotic therapy in patients with UTIs and AB in Peru. Cross-sectional study based on 164 urine cultures and antimicrobial susceptibility testing. A total of 62 cases of AB and 102 of UTI were identified. Women (116, 70.7%) and older adults (60, 36.6%) predominated. A total of 4582 antibiotic prescriptions were recorded, with a therapeutic pattern in both UTI and AB centered on the use of meropenem (540, 21.3%) and (333, 16.3%), vancomycin (221, 8.7%) and (454, 22.2%), ceftriaxone (369, 14.5%) and (176, 8.6%) and ceftazidime (227, 8.9%) and (274, 3.4%), respectively. In general, antibiotic therapy was bactericidal in (87, 53.0%) cases, from the surveillance group in (98, 59.8%) cases, monotherapy in (112, 68.3%) cases, and in cycles of ≤7 days. UTI was associated with a higher burden of comorbidities, including chronic renal failure, hypertension, and diabetes. Fifteen bacterial species were isolated in both clinical entities, with a predominance of Gram-negative bacilli, mainly Escherichia coli and Klebsiella pneumoniae, both of which exhibited high resistance to cephalosporins, sulfonamides, and ampicillin/sulbactam. Among Gram-positive bacteria, Enterococcus faecalis and E. faecium showed resistance to erythromycin, tetracycline, and quinolones. The widespread use of antibiotics from the surveillance group and similar antibiotic therapy in AB and UTI, revealed a critical gap in the implementation of clinical guidelines and the urgent need to accurately differentiate between the two diagnoses to avoid overprescribing and help contain bacterial resistance.

Automated antimicrobial susceptibility testing (AST) may generate carbapenem minimum inhibitory concentration (MIC) results differing from reference methods, complicating recognition of carbapenemase-producing Klebsiella pneumoniae complex isolates. We characterized carbapenem susceptibility discordance in a retrospective discovery cohort of 133 carbapenemase-producing isolates collected in Shenzhen (2004-2017) by comparing imipenem (IPM) and meropenem (MEM) MICs obtained by VITEK 2 and broth microdilution (BMD). Confirmed discordance was defined as repeat-confirmed raw MIC differences of ≥2 log2 dilutions. Features were assessed by whole-genome sequencing, mCIM/eCIM, and exploratory phenotypic assays. Cross-card reproducibility was assessed using an alternative VITEK 2 AST card. A separate retrospectively enriched cohort of 166 K. pneumoniae isolates (2018-2024) was used to evaluate a phenotype-guided reflex-testing workflow. Twenty-nine isolates showed confirmed carbapenem AST discordance, including 28 with IPM discordance. Of these, 27 had raw VITEK 2 IPM MICs at least 2 log₂ dilutions higher than those obtained by BMD, whereas one was reported as resistant after system adjustment despite a low raw MIC. All discrepant isolates carried blaIMP-4 as the sole detected carbapenemase gene, had relatively low carbapenem MICs by BMD, and were distributed across 14 sequence types. Cross-card retesting reproduced the direction of IPM elevation, although the magnitude varied. In a combined internal analysis set of 275 isolates, the phenotype-guided workflow identified unflagged ≥2 log₂ MIC discrepancies with 81.4% sensitivity (95% CI, 67.4%-90.3%) and 92.2% specificity (95% CI, 88.1%-95.0%). These findings define a repeat-confirmed blaIMP-4-associated, IPM-predominant discordance between VITEK 2 and BMD and support phenotype-guided reflex-testing to identify unflagged MIC discrepancies and prioritize confirmatory testing in routine laboratories.IMPORTANCEClinical microbiology laboratories rely on automated systems to support antimicrobial susceptibility interpretation, but these systems may not always recognize method-dependent carbapenem susceptibility discordance. In this study, we show that a specific group of bacteria carrying the blaIMP-4 gene can produce potentially misleading carbapenem susceptibility results, particularly for imipenem, when tested by automated methods. These discrepancies may not be flagged by the instrument and could therefore be overlooked in routine practice. By combining routine laboratory data with genetic analysis and additional testing, we identify a recognizable pattern associated with these hidden discrepancies and examine a phenotype-guided confirmatory workflow to support their laboratory recognition. Our findings highlight the importance of targeted confirmatory testing and provide a framework for local validation of laboratory-actionable carbapenem susceptibility discrepancies, thereby supporting more reliable AST interpretation and antimicrobial resistance surveillance.

Shiga toxin-producing Escherichia coli (STEC), a zoonotic foodborne pathogen, has become a critical global public health issue. This study investigates molecular traits and antimicrobial resistance (AMR) mechanisms of STEC strains derived from retail meat products sourced from domestic production in Liaocheng city, Shandong province, China, to inform health risk assessment. Using quantitative real-time polymerase chain reaction (qPCR), phenotypic AMR testing, and whole-genome sequencing (WGS), 38 STEC isolates were identified from 400 retail meat products, with an isolation rate of 9.5%. Significant differences in STEC isolation rates were detected among different meat types, and mutton exhibited a relatively high isolation rate of 26.09%. Genomic virulence analysis showed that there were higher proportions of single stx2 (58.33%) and dual stx1/stx2 genotypes (33.33%) in mutton isolates than in beef (stx2: 48.00%, dual stx1/stx2: 12.00%), and only the stx2 gene was found in pork isolates. STEC isolates exhibited marked serotypic diversity, including O128ac:H2, O168:H7, O178:H7, O2:H25, and O6:H10. Multilocus sequence typing analysis revealed heterogeneous sequence type (ST) distributions among isolates, with ST10, ST25, and ST2722 as dominant STs, suggesting diverse contamination sources. STEC isolates exhibited high phenotypic resistance to tetracycline (TET) (68.42%), which corresponded to the highest detection rate of the TET resistance gene tet(A) at the genomic level. All isolates were susceptible to ertapenem, meropenem, ceftazidime, ceftazidime-avibactam, ciprofloxacin, and amikacin. Multidrug resistance (MDR) analysis indicated that 16 STEC isolates were MDR strains, with beef-derived isolates having relatively high MDR rates. This study verifies the occurrence of STEC in retail meat, highlighting prevalent AMR and substantial genetic heterogeneity among isolates. The findings underscore the necessity of systematic surveillance to limit STEC transmission along the meat supply chain and facilitate targeted food safety interventions.

ObjectivesCarbapenem-resistant Enterobacterales have emerged as a major global health concern owing to their rapid dissemination and limited therapeutic options. Here we report the first detection of blaOXA-244 in Escherichia coli from the United Arab Emirates (UAE) and characterize two isolates genotypically and phenotypically, comparing them with geographically diverse public strains sharing the same sequence type (ST).MethodsThe isolates were recovered from the urine of a patient with metastatic cancer and from the abdominal fluid of a patient with sepsis. Antimicrobial susceptibility testing, including newer β-lactam and β-lactam/β-lactamase-inhibitors (BL/BLIs), and whole-genome sequencing were performed. Comparative genomic analysis was conducted against global and a defined Middle Eastern/North African subset matched by ST and carbapenemase profile.ResultsThe two isolates were genetically distinct: one carried blaOXA-244 alone and belonged to ST131, whereas the other harboured dual carbapenemases (blaOXA-244 and blaNDM-5) and belonged to ST361. Chromosomal location of blaOXA-244 was confirmed by Southern hybridization. Both isolates were multidrug-resistant, enriched with resistance genes spanning multiple antibiotic classes and virulence genes that support their pathogenicity. Phenotypically, the ST131 isolate remained susceptible to ceftazidime/avibactam and several BL/BLIs combinations, whereas the NDM-5-carrying ST361 isolate was resistant to ceftazidime/avibactam, cefepime/enmetazobactam, and cefepime/taniborbactam, highlighting the therapeutic challenge posed by metallo-β-lactamase co-production. Notably, both isolates remained susceptible to cefepime/zidebactam, cefiderocol, tigecycline, and colistin, and both showed low MICs for meropenem/xeruborbactam. The phylogenetic placement of both UAE isolates is consistent with membership in distinct carbapenem-resistant lineages detected across multiple countries; however, the routes of acquisition could not be inferred.ConclusionsThis is the first report of blaOXA-244 in E. coli from the UAE with two unrelated high-risk backgrounds. A dual OXA-244/NDM-5 ST361 lineage disseminated regionally since 2019 was identified. Because OXA-244 evades routine detection, genomic surveillance is needed to detect such emerging variants and to inform appropriate antimicrobial therapy.

Carbapenem resistance among Gram-negative bacteria remains a serious public health threat, with metallo-β-lactamase (MBL)-producing organisms increasing substantially in prevalence and few therapeutic options available to adequately address these difficult-to-treat pathogens. Cefepime-zidebactam (FEP-ZID) is a novel β-lactam/β-lactam enhancer combination that offers a mechanistically distinct approach to overcoming resistance in Gram-negative organisms. Zidebactam contributes three complementary mechanisms: inhibition of Class A and C β-lactamases, direct antibacterial activity via PBP2 inhibition, and enhancement of cefepime activity through a reduction in the pharmacodynamic exposure required for bactericidal effect, allowing FEP-ZID to achieve substantial reductions in bacterial burden even in isolates with elevated minimum inhibitory concentrations (MICs). FEP-ZID was recently approved in the United States for the treatment of complicated urinary tract infection (cUTI), including acute pyelonephritis, caused by Enterobacterales and/or Pseudomonas aeruginosa. FEP-ZID demonstrates broad in vitro and in vivo activity against isolates producing Class A, B, C, and D β-lactamases, as well as organisms harboring PBP3 alterations that are otherwise associated with reduced susceptibility to currently available MBL-active therapies. This spectrum extends across carbapenem-resistant Enterobacterales, P. aeruginosa, and Acinetobacter baumannii, and includes activity against isolates with porin loss and efflux upregulation, resistance mechanisms that commonly limit the utility of other β-lactam-based agents. In vivo infection models utilizing humanized regimens have demonstrated bactericidal activity against isolates with FEP-ZID MICs up to 64 μg/mL. The Phase 3 ENHANCE I trial demonstrated noninferiority and subsequent superiority over meropenem in cUTI (including acute pyelonephritis), driven primarily by microbiological response, with favorable outcomes observed across many baseline pathogens, including extended-spectrum β-lactamase-producing isolates and patients with concomitant bacteremia. Compassionate use experience further suggests possible utility in severe multidrug-resistant infections across multiple infection types, including bloodstream, osteoarticular, and intra-abdominal infections caused by MBL-producing organisms. Collectively, available preclinical and clinical evidence positions FEP-ZID as a mechanistically distinct option for difficult-to-treat Gram-negative infections, with additional clinical study needed to define its role beyond the currently approved indication.

Carbapenem-resistant Gram-negative bacteria (CRGNB)-including carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Pseudomonas aeruginosa (CRPA), and carbapenem-resistant Acinetobacter baumannii (CRAB)-pose a critical threat to public health due to their high associated morbidity and mortality. Key resistance mechanisms involve carbapenemase production, porin mutations, efflux pump overexpression, penicillin-binding proteins (PBPs) alterations, and biofilm formation, with prevalence varying geographically and by species. Effective management requires identifying the infection site, assessing disease severity, and determining the pathogen and its resistance profile to guide antimicrobial selection. Recommended agents include ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, aztreonam-avibactam, ceftolozane-tazobactam, sulbactam-durlobactam, colistin, and tigecycline. For CRE, treatment depends on the carbapenemase type: KPC-producing strains are managed with novel β-lactam/β-lactamase inhibitor combinations (ceftazidime-avibactam, imipenem-relebactam, meropenem-vaborbactam); MBL-producing strains with ceftazidime-avibactam plus aztreonam or aztreonam-avibactam; and OXA-48-type-producing strains with ceftazidime-avibactam alone. For CRPA, ceftolozane-tazobactam is the primary option, while CRAB is treated with sulbactam-durlobactam-based combination therapy. However, disparities in treatment access persist; while these novel agents are recommended, alternative salvage strategies are often required in resource-limited settings. This review details the epidemiology of CRGNB, outlines pathogen-specific resistance mechanisms and corresponding therapies, highlights knowledge gaps, and suggests future directions to inform prevention and treatment efforts.

Carbapenems and polymyxins are critically important antimicrobial agents for treating severe infections caused by multidrug-resistant Gram-negative bacteria. The global dissemination of the carbapenem resistance gene bla NDM and colistin resistance gene mcr-1 threatens the effectiveness of these last-line antibiotics. From a One Health perspective, food-producing animals and retail meat products may serve as reservoirs and vehicles for antimicrobial resistance determinants. This study investigated the occurrence and genomic characteristics of bla NDM-5- and mcr-1-coharboring Escherichia coli recovered from retail chicken meat to characterize their potential for dissemination through the food chain. Among 67 retail meat samples collected in Xuancheng, China, two meropenem-resistant E. coli isolates carrying both bla NDM-5 and mcr-1 were recovered exclusively from chicken meat. Antimicrobial susceptibility testing and hybrid whole-genome sequencing revealed that the isolates belonged to ST155 and ST165 and exhibited multidrug resistance. Phylogenetic analysis showed that both isolates were genetically distinct from global genomes of the same ST carrying bla NDM and/or mcr-1, suggesting that the two isolates were not derived from recent clonal dissemination represented in the analyzed dataset. Complete genome analysis identified two distinct plasmid organizations of bla NDM-5- and mcr-1: one isolate carried bla NDM-5 and mcr-1 on separate plasmids, whereas the other harbored both genes on a single conjugative IncHI2 plasmid. Comparative genomic analyses demonstrated high similarity between these plasmids and plasmids reported from humans, animals, and food sources. These findings highlight that poultry-associated E. coli may serve as carriers of important resistance determinants with potential for plasmid-mediated dissemination, emphasizing the need for integrated One Health genomic surveillance.

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a rare but serious drug reaction that can be life-threatening. This report reviews a case of a male in his 30s with a history of extensive burn injuries, osteomyelitis, and bipolar disorder who was admitted to the hospital for left foot osteomyelitis after failing home intravenous (IV) piperacillin-tazobactam treatment. On hospital day 4, the patient began to develop a progressive macular rash. Laboratory results were significant for worsening transaminitis and elevated eosinophil levels, concerning for DRESS. Active inpatient medications included aripiprazole, lamotrigine, vancomycin, and meropenem. Lamotrigine and all antibiotics were discontinued in the setting of suspected DRESS. Treatment was initiated with IV methylprednisolone 175 mg daily, with a taper over eight to 12 weeks, and an infusion of N-acetylcysteine for liver injury, with eventual improvement of liver enzymes to baseline and resolution of eosinophilia. This case underscores the importance of prompt recognition of DRESS in patients with polypharmacy and complex infectious disease management.