Journal of Antimicrobial Chemotherapy

Long-acting cabotegravir and rilpivirine combination (LA-CAB/RPV) is approved for HIV treatment whilst long-acting cabotegravir alone (LA-CAB) is approved for HIV prevention, both in adults. However, individuals who become pregnant might prefer to discontinue it due to lack of definitive data on safety. The aim of this study was to characterise the tail-phase maternal and fetal pharmacokinetics of LA-CAB/RPV following discontinuation at steady-state early in pregnancy. A virtual population of non-pregnant women (n = 100 per scenario) initiated intramuscular injections of LA-CAB/RPV at the approved dosage and continued maintenance dose (400/600 mg once monthly or 600/900 mg once every two months) until steady state. We simulated discontinuation at steady state after only one injection during pregnancy. Tail-phase pharmacokinetics of CAB and RPV from LA injections were characterised during gestation and until 6 months postpartum. Pharmacokinetic tails of LA-CAB/RPV were driven by the residual drug in the muscle depot which stabilised at steady state and reduced steadily upon dosing discontinuation. Upon discontinuation of the monthly dosing, predicted median (IQR) maternal plasma concentrations for LA-CAB were 415 (386-448) ng/mL at delivery and 125 (115-139) ng/mL 6 months postpartum. For LA RPV, these were 11.6 (11.0-12.6) ng/mL and 7.84 (7.30-8.49) ng/mL at delivery and 6 months postpartum, respectively. Pharmacokinetic tails of LA-CAB/RPV extend to several months postpartum, with levels falling below established minimum effective concentration in most women after gestation week 33. Potential strategies to minimise potential risks associated with LA-CAB/RPV discontinuation in this population are needed.

Cefiderocol exhibits excellent in vitro activity against Pseudomonas aeruginosa; however, resistance can emerge. We investigated the molecular mechanisms underlying cefiderocol resistance (MIC >2 mg/L) in 103 clinical strains collected from 61 hospitals (2021-2024). MICs ranged from 4 to >128 mg/L, with 39.8% of strains showing MICs >8 mg/L. Although 37.8% were classified as difficult-to-treat resistant (DTR), acquired {beta}-lactamases were detected in 72.8% of strains, including carbapenemases (39.8%), mainly NDM-1 (29.1%), and Extended Spectrum {beta}-Lactamases (ESBLs) (38.8%). Cloning of 11 {beta}-lactamases into pUCP24, including the acquired cephalosporinase PAC-1 and ESBLs (VEB-1, and VEB-9), resulted in marked increases in cefiderocol MICs (up to 128-fold). Introduction of 6 mutations in the PDC enzyme into a PAO1{Delta}blaPDC-1 background increased MICs up to 4 mg/L and conferred cross-resistance to ceftolozane/tazobactam, notably F121L, G157D, T70I, and E219K. Alterations in siderophore transporters or regulators were identified in 38.8% of strains, most frequently a PirR frameshift (R132fs), consistent with PirR inactivation, which was confirmed in the PAO1 strain to contribute to cefiderocol resistance. Overall, cefiderocol resistance in clinical strains is multifactorial, mainly involving acquired {beta}-lactamases (ESBLs, carbapenemases) and impaired siderophore uptake (PiuA/PiuD, PirA, PiuC), leading to high-level resistance (>8 mg/L). The polyclonal distribution and diversity of mechanisms highlight the need for routine susceptibility testing and surveillance. Detection of NDM producers is critical, as cefiderocol should be used with caution in this context.

Background: Antimicrobial resistance (AMR) is a global public health problem. Infections caused by extended-spectrum beta-lactamase (ESBL) and carbapenemase (CP) -producing Enterobacterales (E) threaten individuals and healthcare systems worldwide. Symptomatic infection caused by Enterobacterales is typically preceded by asymptomatic colonisation and often occurs in the most vulnerable individuals, thus interrupting asymptomatic transmission is desirable. The dominant transmission routes across the healthcare continuum including hospitals, intermediate care, and long-term care facilities are not well understood. Methods: Here we present a protocol describing a genomic surveillance framework developed for the Tracking Antimicrobial Resistance Across Care Settings (TRACS) Liverpool programme, which aims to identify critical ESBL-E transmission points in hospitals and care homes in Liverpool, UK. Our study integrates individual participant and healthcare facility data, validated standard operating procedures for taking and culturing stool, rectal, environmental, and staff samples, and genomic sequencing of ESBL-E, and statistical modelling approaches into a research framework for ESBL-E genomic surveillance. Discussion: There is a need for improved epidemiological and laboratory approaches to studying bacterial transmission. Drug-resistant enteric bacteria are a highly tractable marker of the movement of all enteric bacteria, and interventions designed to interrupt transmission of drug-resistant bacteria are expected to have a broader healthcare impact. This protocol provides a standardised, reproducible approach for identifying ESBL-E, tracking acquisition events, and linking clinical and environmental isolates through whole-genome sequencing.

APC148 is a novel metallo-beta-lactamase inhibitor with broad activity against Ambler class B enzymes including NDM, VIM and IMP. It is being developed for patients with serious infections caused by multidrug-resistant Gram-negative bacteria. APC148 is combined with the broad-spectrum beta-lactam antibiotic meropenem and the serine-beta-lactamase inhibitor avibactam, which targets Ambler class A, C, and some class D (OXA-48-like) enzymes. In combination with meropenem and avibactam, APC148 demonstrated superior in vitro activity against a global, multidrug resistant collection of Enterobacterales, showing its promising activity against beta-lactamase producing pathogens. In this randomized, placebo-controlled, first-in-human study, the safety, tolerability and pharmacokinetics of APC148 were evaluated in healthy adults. Single doses ranging from 50 mg to 760 mg APC148 were administered intravenously over 3 h to 46 participants across six dose groups. APC148 was well tolerated at all dose levels. All adverse events were of mild intensity, and no serious adverse events or adverse events leading to study- or treatment discontinuation occurred. The pharmacokinetics of APC148 were dose-proportional with low plasma clearance, low to moderate volume of distribution and a mean plasma half-life of 2.6 h. APC148 is well tolerated in humans at therapeutically relevant doses and represents a promising candidate in the fight against antibiotic-resistant bacteria. (This study has been registered at ClinicalTrials.gov under registration number NCT06360640).

ObjectivesMultidrug-resistant (MDR) Klebsiella pneumoniae is an increasingly important cause of recurrent urinary tract infections (UTIs), particularly in high-risk patients such as those with neurogenic bladder, where therapeutic options are limited. Bacteriophage therapy represents a promising alternative, but pre-clinical models and characterization of phages active against UTI-derived strains remain scarce. We therefore aimed to isolate and characterize bacteriophages targeting a clinical MDR K. pneumoniae strain causing recurrent UTI and evaluate their activity under urinary conditions. MethodsThree bacteriophages were isolated from environmental samples using an ESBL-producing K. pneumoniae clinical isolate obtained from a neurogenic bladder patient. Phages were characterized by genome sequencing, electron microscopy, stability assays, one-step growth curves, and host-range analysis across 79 clinical UTI isolates. Phage activity was quantified in LB medium and human urine using bacterial growth kinetics and a lytic activity score. ResultsThree lytic phages from the former siphoviridae family (EDIRA083, EDIRA088, and EDIRA092) belonging to distinct genera were identified. Genomic analysis confirmed the absence of lysogeny-associated, virulence, or antibiotic-resistance genes. Latent periods ranged from 8 to 40 minutes and burst sizes from 38 to 170 virions per infected bacterium. Host-range analysis revealed narrow activity for EDIRA083 and EDIRA088, whereas EDIRA092 infected 29% of the 79 clinical isolates tested. In liquid phage infection assays, overall lytic activity was consistently higher and more sustained in human urine than in LB, suggesting reduced fitness of resistant mutants under urinary conditions. ConclusionsThese results identify three genetically distinct lytic phages targeting MDR K. pneumoniae and highlight the importance of testing phage activity under infection-relevant conditions. Their activity in urine supports further evaluation of these phages as candidates for therapeutic development against MDR Klebsiella UTI.

Urinary tract infections (UTIs) are among the most common infectious diseases worldwide, with Escherichia coli being the predominant uropathogen. The increasing prevalence of extended-spectrum beta-lactamase (ESBL)-producing strains and their association with fluoroquinolone resistance pose a significant challenge to empirical therapy, particularly in community settings. The aim of this study was to determine the epidemiology and predictive factors associated with ESBL-producing E. coli and its concomitant fluoroquinolone resistance in community-acquired clinical isolates. A retrospective cross-sectional study was conducted analyzing 244 clinical E. coli isolates. Demographic and microbiological data were collected, including age, sex, sample type, and antibiotic susceptibility. Associations between variables and ESBL production were assessed using Pearsons chi-squared test, and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Of the isolates, 165 (68%) were ESBL-producing. A significant association was observed between age group and ESBL production (p < 0.001), with the highest frequency in the 20-39 age group. Most ESBL-positive isolates were obtained from women (73%), although odds ratio (OR) analysis suggested a non-significant trend toward a higher probability in men (OR = 1.29; 95% CI: 0.72-2.31). High rates of fluoroquinolone resistance were identified among the ESBL-producing isolates, with 30% resistance to levofloxacin and 35% to ciprofloxacin (p < 0.001). Urine samples showed the highest concentration of ESBL-positive isolates, with a significant association between sample type and resistance (p < 0.001). The high prevalence of ESBL-producing E. coli and its concomitant resistance to fluoroquinolones highlight a critical challenge for the empirical treatment of urinary tract infections in Mexico, underscoring the need to strengthen antimicrobial use management and local surveillance strategies.

Klebsiella pneumoniae ST383 has emerged as a high-risk clone, characterized by carbapenem resistance and increasing detection of hypervirulence determinants. We describe a novel ST383 lineage in Lebanon, defined by the acquisition of ICEKp5, which carries the yersiniabactin locus. Three ST383 K. pneumoniae clinical isolates (LBN_CAKp91, LBN_CTKp3, LBN_CTKp11) recovered from a Lebanese medical center were subjected to whole-genome sequencing. Comparative genomic analysis included regional ST383 strains and previously characterized Lebanese isolates. The study isolates formed a tight, monophyletic cluster (3-9 SNPs) that is phylogenetically distinct from the previously reported Lebanese ST383 clone (>164 SNPs) and grouped most closely to an Egyptian ST383 strain (59-65 SNPs). All three isolates carried ICEKp5 with yersiniabactin lineage ybt14, a feature absent in the earlier Lebanese ST383 clone. The isolates were the only ST383 strains to harbor the full spectrum of hypervirulence determinants to date, including capsule regulators (rmpA, rmpA2), aerobactin (iucABCD, iutA), yersiniabactin, and the hypervirulence biomarker peg-344. All isolates carried dual carbapenemases (blaOXA-48 and blaNDM-5) in addition to blaCTX-M-15 and blaCTX-M-14b. The genetic environments of blaOXA-48 and blaNDM-5 were highly conserved across geographically diverse ST383 isolates, indicating common plasmid origins. This study documents the emergence of a novel hypervirulent extensively drug-resistant (XDR) ST383 K. pneumoniae lineage in Lebanon. The acquisition of ICEKp5, combined with plasmid-borne hypervirulence and resistance determinants, reveals the concerning convergence of hypervirulence and XDR. Enhanced surveillance and infection control measures are urgently needed to monitor this emerging high-risk clone.

The incidence of vancomycin-resistant Enterococcus (VRE) is rising in hospitals in Canada, and resistance to last-resort antimicrobials including linezolid complicates treatment options for multidrug-resistant isolates. Recent reports from around the globe indicate that both linezolid and vancomycin resistance genes can be co-carried and mobilized by linear plasmids (named pELF) in Enterococcus species, often on the same backbone. We aimed to investigate linezolid resistance and linear plasmid prevalence in VRE bloodstream infection isolates collected by the Canadian Nosocomial Infection Surveillance Program from 2009 to 2024. We found that screening for pELF linear plasmid ends in short reads was a reliable way to predict linear plasmid presence in large-scale surveillance data (100 % accuracy on 85 reference samples). Almost half of the isolates in our collection were predicted to carry pELF plasmids (45.4 %, 941/2071) and we found that this proportion has increased from 2018 (32.2 %, 59/183) to 72 % of isolates between 2021 and 2024 (2021: 68.5 % (115/168); 2022: 71.6 % (146/204); 2023: 72.8 % (166/228); 2024: 71.6 % (235/328)). This trend of increasing linear plasmid carriage is evident from 2018 to 2024 across the dominant emerging sequence types (ST80, ST17, ST117). Linezolid resistance based on phenotypic antimicrobial susceptibility testing was low (1.0 %, 21/2071). Using long read sequencing, we characterized the linezolid resistant isolates and confirmed pELF plasmid presence in 13/21 (61.9 %) isolates. Six isolates harboured pELF plasmids encoding linezolid resistance genes (optrA, cfr(D), poxtA) and five of these also encoded vancomycin resistance genes (vanA). We compared these six plasmids to 39 public plasmid sequences and clustered them using MOB-suite and pling. Overall, this study provides further examples of the co-carriage of vancomycin and linezolid resistance genes on mobile linear plasmids and shows that linear plasmid prevalence is detectable and increasing across VRE in Canada. IMPACT STATEMENTGiven the increasing prevalence of multidrug-resistant hospital-acquired pathogens, resistance to last-resort antibiotics is a global public health threat. Linezolid is a last-resort antibiotic used to treat vancomycin-resistant Enterococcus isolates, and the dissemination of linezolid resistance genes is significantly facilitated by mobile elements that can transfer between unrelated strains and species. Linezolid resistance genes have recently been described on linear plasmids and are often co-localized with other resistance genes on the same plasmid backbone. Consequently, understanding the features and distribution of linear plasmids and those harbouring linezolid resistance genes is crucial for pathogen surveillance and mitigation of resistance. In this work, we used long-read and short-read sequencing to characterize genomic epidemiology of linear plasmids across 16 years of Enterococcus surveillance data in Canada. This study furthers knowledge of linear plasmids by demonstrating that they are relatively common across vancomycin-resistant Enterococcus blood isolates and by providing more examples of co-localized vancomycin and linezolid resistance genes on the same linear plasmid backbone. DATA SUMMARYSequencing data and genome sequences were deposited in National Centre for Biotechnology BioProject PRJNA1279082, and accessions are listed in Table S1. Supplementary materials for this study are available at the Figshare portal through DOI: XXX.

BackgroundPhage therapy is increasingly considered a promising alternative for treating multidrug-resistant (MDR) infections. However, its clinical application remains limited by challenges in isolating effective phages against resistant clinical strains and by the limited ability of in vitro assays to predict performance in real biological environments. While biological matrices are known to influence phage activity, these effects are not well characterised. MethodsA phage-resistant Pseudomonas aeruginosa isolate from a patient with recurrent MDR urinary tract infection was used as the model organism. Conventional isolation methods failed to recover effective phages, leading to the development of TEASER-i (Transient EDTA- and Ion-Assisted Sequential Enrichment & Recovery). Recovered phages were characterised using adsorption assays, one-step growth kinetics, and time-kill experiments. Their antibacterial activity was evaluated both in vitro and in ex vivo human matrices (whole blood, serum, plasma, and urine). Phage efficacy was quantified using maximum log reduction (Emax), area under the curve (AUC), and phage-to-bacteria ratio (PBR). ResultsA novel TEASER-i method optimised for difficult-to-treat Gram-negative infections, enabled recovery of a functionally effective Osewage-derived P. aeruginosa phage, which outperformed a Ourine-derived P. aeruginosa phage that showed slower replication and lower burst size. Phage activity varied significantly in blood, serum, and plasma. Urine supported the most sustained antibacterial effect. In many cases, early bacterial reduction was followed by regrowth. Sustained activity was associated with maintenance of favourable PBR values, while negative PBR corresponded to treatment failure. At 96 h, only two conditions maintained favourable phage load (log 10 PBR > 0): the S. aureus phage in urine (+1.66) and the sewage-derived P. aeruginosa phage in serum (+1.32). ConclusionsPhage efficacy depends not only on intrinsic lytic capacity but also on the ability to persist and amplify within specific biological environments. Conventional isolation and in vitro screening may therefore overestimate therapeutic potential. Combining optimised isolation strategies with ex vivo evaluation provides a more realistic framework for phage selection and clinical translation.

The global dissemination of Enterobacterales producing both metallo-{beta}-lactamases (MBLs) and serine {beta}-lactamases (SBLs) represents a critical threat to modern medicine, as no currently marketed antibiotics effectively target MBL-mediated resistance. APC148 is a novel, selective zinc-chelating MBL inhibitor designed to restore {beta}-lactam activity in MBL positive isolates, when used in combination with a broad-spectrum carbapenem. In this study, we evaluated the in vitro efficacy of APC148 in triple combinations with either meropenem-avibactam (APC301) or cefepime-avibactam (APC302) against a diverse global collection (JMI collection) of 176 MBL- and SBL-producing Enterobacterales isolates (including NDM, VIM, and IMP variants). Using broth microdilution, the triple combinations were compared against several newly approved and late-stage pipeline antibiotic products. Both APC301 and APC302 demonstrated superior potency, achieving a MIC90 of 0.12 {micro}g/mL. When applying CLSI breakpoint interpretive criteria for the parent {beta}-lactams, 99.4% of the MBL and SBL-containing isolates were susceptible to APC301, while 97.2% were susceptible to APC302. These results indicate that the addition of a selective MBL inhibitor to an SBL-inhibitor/{beta}-lactam antibiotic effectively bypasses complex co-existing {beta}-lactam resistance mechanisms in multidrug-resistant (MDR) pathogens. Given that MDR Enterobacterales frequently harbor multiple {beta}-lactamase classes simultaneously, these triple combinations constitute a highly promising clinical strategy to address the therapeutic void in MBL-mediated resistance

The Burkholderia cepacia complex (BCC) is comprised of 24 species of Gram-negative bacteria that cause opportunistic infections. While antimicrobial susceptibility testing (AST) has historically been used to guide treatment for BCC infections, recent work highlighting problems with AST for these organisms led the Clinical and Laboratory Sciences Institute (CLSI) to remove disk diffusion (DD) and minimal inhibitory concentration (MIC) breakpoints for BCC from its M100 standards document. Epidemiological cut-off values (ECVs) may be helpful to clinicians in the absence of breakpoints, as they may be used to determine whether an isolate has a wild-type or non-wild-type phenotype. Here we present an analysis of BCC ECVs for ceftazidime (CAZ), levofloxacin (LVX), meropenem (MEM), minocycline (MIN), and trimethoprim-sulfamethoxazole (TMP-SMX). ECVs were calculated using MIC data from 3 previous studies and 3 independent laboratories for 1,896 BCC isolates. ECVs were 16 g/ml for CAZ, 8 g/ml for LVX, 16 g/ml for MEM, and 8 g/ml for MIN. The ECV for TMP-SMX varied depending on the analysis from 2 g/ml, 8 g/ml, and 16 g/ml and therefore could not be reliably established. Challenges with establishing ECVs for BCC include limitations with the pooled MIC dataset, broad MIC distributions, and high ECVs that are above the obsolete susceptible MIC breakpoints. These challenges limit the clinical utility of ECVs for these organisms and supported removal of ECVs from the CLSI M100 standards document. IMPORTANCEThe Burkholderia cepacia complex is a group of bacterial species that cause difficult-to-treat opportunistic infections. Recently, clinical breakpoints, which are used to determine whether organisms are susceptible to certain antimicrobials, were removed from Clinical and Laboratory Standards Institute (CLSI) standards for these organisms due to problems with antimicrobial susceptibility testing performance. Clinicians are now faced with the challenge of how to treat these complex infections without clinical breakpoints. Here we determine epidemiological cut-off values (ECVs) for relevant antimicrobials for the B. cepacia complex. While we established ECVs for four antimicrobials, we encountered significant challenges in our analyses, including limitations with data for these organisms and high ECVs that are not clinically useful. These challenges limit the practical use of these ECVs in helping guide clinicians on treatment and supported the eventual removal of ECVs from the CLSI M100 standards document.

ObjectivesTo identifiy risk factors for antimicrobial resistance (AMR) in seven pathogen-antimicrobial combinations in patients with cancer and cancer survivors. MethodsUsing data from patients with recent or past cancer diagnostic codes in Oxfordshire, UK, we examined associations between 22 potential risk-factors and AMR in blood culture isolates, collected between 1-April-2015 and 31-March-2025. ResultsAmong 5,975 bacteraemias in 4,365 adults, we analysed 3,141 (52.6%) due to Enterobacterales and 620 (10.4%) due to Enterococcus faecalis/faecium in 2,752 patients. Fourteen risk-factors for antimicrobial-resistant bacteraemia were identified, varying across pathogen-antimicrobial combinations. Compared with no previous antimicrobial susceptibility test result, prior resistance to the same antibiotic in any culture in the last year was strongly associated with AMR across all pathogen-antimicrobial combinations (all p[&le;]0.001). Prior antibiotic exposure and younger age were also positively associated with AMR in four and five combinations, respectively. Cancer type showed modest effects; lymphoid/haematopoietic malignancies were associated with higher odds (vs colorectal cancer) of trimethoprim-sulfamethoxazole-resistant Enterobacterales (aOR=2.07 95%CI 1.40-3.06) and vancomycin-resistant Enterococcus bacteraemia (aOR=6.68, 1.21-36.91). ConclusionsPrevious resistance was the greatest risk factor for bacteraemia with AMR in cancer patients and survivors, with prior antibiotic exposure and age also contributing. Lymphoid/haematopoietic malignancies increased risk of resistance to specific antimicrobials. Keywords: antimicrobial resistance, bacteraemia, cancer, risk factors

Objectives: Optimising parenteral antimicrobial use is central to antimicrobial resistance (AMR) control, yet its appropriateness is difficult to assess. We aimed to develop a quantitative indicator to evaluate the appropriateness of parenteral antimicrobial therapy in hospitalised patients with bloodstream infections. Methods: We developed the Susceptibility-Spectrum Discrepancy Index (S2DI), reflecting the discrepancy between antimicrobial susceptibility of blood culture isolates and the spectrum width of prescribed agents. Using a database from 67 National Hospital Organization hospitals in Japan, we identified patients with Staphylococcus aureus or Escherichia coli bacteraemia from 2017 to 2023. An expert panel of 10 infectious disease physicians independently ranked antimicrobial susceptibility (A) and spectrum width of commonly used agents (B). S2DI was defined as B minus A on day 7 after treatment initiation, with values closer to zero indicating more appropriate therapy. S2DI was calculated for individual cases, aggregated at the hospital level, and analysed using linear mixed-effects models with hospital-level random effects. Results: A total of 4,505 S. aureus and 9,563 E. coli bacteraemia cases were included. Median S2DI was 1 (IQR 0-1) for S. aureus and 2 (IQR 0-3) for E. coli. For both pathogens, later calendar years were significantly associated with more favourable S2DI, suggesting gradual improvement in antimicrobial use. In E. coli bacteraemia, female sex and younger age were also associated with more appropriate therapy. Conclusions: Although variation across hospitals persists, appropriateness of parenteral antimicrobial use has improved over time. S2DI is a simple metric that may support optimisation of antimicrobial use.

BACKGROUNDAutomated antimicrobial susceptibility testing (AST) systems are crucial for accurate, timely detection of drug-resistant microbial isolates. This meta-analysis assessed the performance of the BD Phoenix ("Phoenix", BD Diagnostic Solutions), Vitek(R) 2 ("Vitek 2", bioMerieux), and DxM MicroScan WalkAway ("MicroScan", Beckman Coulter, Inc.) AST systems relative to common reference methodology. METHODSA systematic literature search in Ovid (MEDLINE and Embase) yielded 275 unique (not duplicated) records, with 44 additional records retrieved from handsearching; 39 studies met inclusion criteria. Categorical agreement (CA), essential agreement (EA), very major errors (VMEs), and major errors (MEs) for the three instruments were compared to a common reference method. Ratios of proportions were analyzed using random-effect meta-regression. RESULTSThe instruments did not differ significantly in CA, EA, or ME. Vitek 2 showed a higher overall VME rate than Phoenix ([~]44% higher; Vitek 2-to-Phoenix ratio = 1.44; p=0.062 [approaching significance]) and MicroScan (74% higher; ratio = 1.74; p=0.045). No appreciable difference was observed for VME between Phoenix and MicroScan. Subgroup analyses should be interpreted cautiously due to limited overall significance indicating varying performance across systems. Vitek 2 generally had higher relative VMEs for gram-negative organisms and lower relative VMEs for gram-positive organisms, whereas Phoenix showed the opposite pattern. MicroScan had relatively low VMEs when stratified by Clinical and Laboratory Standards Institute (CLSI) criteria; no differences in VMEs were observed using European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. CONCLUSIONAlthough some VME differences were noted, overall performance of the three systems was comparable. Organism- and drug-specific VME patterns--and updates to CLSI criteria over time--highlight the importance of continued monitoring of current breakpoints for all three instruments.

Many studies have identified antibiotic resistant (ABR) Escherichia coli on meat. Appropriate hand hygiene and cooking practices should minimise the risk of gastrointestinal colonisation with ABR E. coli found on meat, and the subsequent chance of causing resistant opportunistic extraintestinal infection. There are large gaps in our understanding of the prevalence, origins and zoonotic potential of ABR E. coli found on meat, however, and particularly for meat reared in extensive farming systems. Wales is a devolved nation within the United Kingdom having large populations of extensively-reared sheep and beef cattle. To help address knowledge gaps around ABR E. coli on extensively reared meat, therefore, beef mince and lamb loin/leg steaks/chops were purchased from 50 (beef) and 46 (lamb) independent butchers across Wales. Following enrichment culture, 200 g meat samples were found to be positive for E. coli resistant to amoxicillin (31% positivity), streptomycin (28%), spectinomycin (29%), amoxicillin-clavulanate (11%), 3rd generation cephalosporins (2%) and fluoroquinolones (5%). Phylogenetic analysis confirmed that Welsh lamb meat ABR E. coli isolates (n=79) are more closely related to those found in faecal samples collected around sheep (n=352) than around beef cattle (n=361) on Welsh farms. This suggests that faecal contamination at or around slaughter is their primary origin. We found no closely related meat/infection clones (<20 SNPs distant and the same antibiotic resistance genes) when comparing ABR E. coli from Welsh meat (n=92) and those causing extraintestinal infections in people (n=2387) in an English region bordering Wales. We conclude, therefore, that the wider zoonotic implications of finding ABR E coli on beef and lamb meat sold at independent butchers in Wales are small.

WHO recommends bedaquiline-pretomanid-linezolid- (BPaL) and BPaL-moxifloxacin (BPaLM) for treatment of rifampicin-resistant tuberculosis, informed by the TB-PRACTECAL results. However, clinical explanatory data of these drugs exposure and Mycobacterium tuberculosis clearance rates and toxicity relationships remain understudied. We therefore investigated the relationship between the patients exposure to anti-TB drugs in TB-PRACTECAL trial investigational regimens and their treatment outcomes. PRACTECAL-PKPD was a prospective pharmacokinetics and pharmacodynamics study nested in TB-PRACTECAL. Patients with rifampicin-resistant pulmonary tuberculosis were enrolled from Belarus and South Africa. The first objective was to develop drug exposure metrics for bedaquiline, pretomanid, linezolid, moxifloxacin and clofazimine. The efficacy objectives were to establish an exposure-response model for each drug and regimen to both bactericidal activity and long-term treatment outcomes. The safety objective was to investigate the exposure-toxicity relationship of each drug. Antimicrobial exposure did not correlate with the speed of sputum bacterial clearance, however there was a 20% increased bacillary killing rate with BPaLM compared to the standard of care arm whilst BPaL and BPaL-clofazimine (BPaLC) displayed a 15% decreased bacillary killing rate compared to the standard of care arm. Linezolid plasma exposure was higher amongst patients with anaemia or neutropenia compared to those without. No other exposure-toxicity relationships were identified for all other drugs. Absence of correlation between drug exposure and bacillary clearance suggest that the dosages used achieve saturation of bacillary killing, while remaining safe.

Background: Conjugative plasmids encoding New Delhi metallo-beta-lactamase (blaNDM) pose a threat for the spread of carbapenem resistance among healthcare acquired pathogens. Plasmid-associated outbreaks of blaNDM-producing bacteria can involve multiple bacterial species and persist over long time periods, making their detection and control difficult. We systematically studied the genomic epidemiology of blaNDM-encoding plasmids detected within a single hospital system over a five-year period. Methods: blaNDM-producing isolates were collected from clinical cultures as part of the Enhanced Detection System for Healthcare-Associated Transmission (EDS-HAT) genomic sequencing active surveillance program, or during infection prevention and control (IP&C) investigations. Isolates were identified as blaNDM producers by polymerase chain reaction (PCR); the presence of plasmid-encoded blaNDM genes was confirmed by sequencing on both Illumina and Oxford Nanopore platforms. Plasmids were clustered using Pling and bacterial relatedness of host isolates was evaluated with split kmer analysis. Electronic health record data were used to identify shared unit-level spatiotemporal exposures and epidemiologic links within both plasmid and host clusters. Results: We identified 61 blaNDM-producing isolates collected from 54 patients sampled between November 2020 and July 2025. Isolates belonged to 15 Enterobacterales species; Enterobacter hormaechei was the most frequently sampled species (n=23, 37%), and blaNDM-5 was the most frequently observed blaNDM allele (n=36, 59%). We observed six clusters of genetically similar blaNDM-encoding plasmids each containing 2-28 isolates, and eight singleton plasmids. The two largest plasmid clusters consisted of a highly conserved 46 kb IncX3 family blaNDM-5-encoding plasmid (n=28 plasmids, 9 species) and a more variable 98-201 kb IncC family blaNDM-1-encoding plasmid (n=12 plasmids, 6 species). Epidemiologic investigation paired with whole genome sequencing identified spatiotemporal associations between shared patient exposures and putative plasmid and bacterial transmission clusters, suggesting that unit-level exposures contribute to plasmid dissemination. Finally, analysis of publicly available sequences showed that the most prevalent plasmids detected, IncX3(blaNDM-5) and IncC(blaNDM-1), also demonstrated high global prevalence. Conclusions: This study demonstrates the diversity of blaNDM carrying plasmids within a single hospital system and their capacity to cause prolonged, multispecies outbreaks. Integrating whole genome sequencing with epidemiologic data identified unit-level spatiotemporal overlap as a likely contributor to plasmid dissemination in the hospital.

Antimicrobial resistance (AMR) is classified by the World Health Organization (WHO) as one of humanity's ten global public health threats. This review aimed to estimate the prevalence, temporal trends and regional distribution of AMR in WHO priority bacteria across human, animal and environmental sources in Cameroon. This review was conducted following PRISMA 2020 guidelines, with the protocol registered in PROSPERO. A systematic literature search was conducted in Google Scholar, PubMed, African Journals Online, Hinari, and Africa indexus Medicus. Random effects models were used to estimate pooled prevalence and 95% confidence intervals (CIs), with subgroup analyses by bacterial source, region, and sampling period. Of 1566 articles screened, 115 met the inclusion criteria. The reported data encompassed 16 bacteria-antibiotic combinations in 16,948 isolates. Globally, third-generation cephalosporin (3GC) resistance in E. coli was the most prevalent (49.0%, 95% CI: 39.0-60.0%, I2=97.7%), reaching 77.0% (95% CI: 46.0-98.0%, I2=95.6%) in environmental isolates. The pooled prevalence of ESBL production in all included Enterobacterales was 37.0% (95% CI: 30.0-45.0%). Most of the highest resistance rates were observed in the Littoral region. The resistance rates between 2016 and 2025 were significantly higher than those from 2000 to 2015. These increases were more marked in fluoroquinolone-resistant Salmonella spp (1.0% to 48.0%, I2=97.3%, p<0.001), carbapenem-resistant E. coli (0% to 15%, I2=93.5%, p<0.001), and 3GC-resistant E. coli (34.0% to 64.0%, I2=97.6%, p=0.003). Antimicrobial resistance in WHO priority bacteria in Cameroon is high, unevenly distributed across regions and significantly increasing over time. These results underscore the crucial need for strengthened AMR surveillance to curb the growing threat of AMR in Cameroon.

BackgroundMetronidazole (MTZ) is a first-line antibiotic for several enteric infections. Its use is common in low-income countries, where most primary-care consultations are conducted by nurses. However, increasing resistance among some enteric pathogens is a growing concern. Using WHO guidelines, we conducted a register-based cross-sectional study to assess MTZ prescribing practices and their determinants in public and private primary healthcare facilities in South Benin. MethodsWe performed a register-based cross-sectional study covering the year 2020 in 11 primary healthcare facilities (5 public and 6 private) in Abomey-Calavi, South Benin, following WHO recommendations. In total, 200 visits per facility were selected using systematic random sampling. The primary outcome was the prevalence of MTZ prescription. Determinants of MTZ prescription were identified using multivariable logistic regression analysis. ResultsIn total, 2,200 medical visits were analyzed. The median age of patients was 19 years, and 57% were female. Antimalarials were prescribed in 52% of visits. Antibacterial agents were prescribed in the majority of visits, with MTZ being the second most frequently prescribed antibiotic (18%), after aminopenicillins (27%). In multivariable analysis, digestive symptoms (adjusted odds ratio [aOR], 8.65; 95% confidence interval [CI], 6.49-11.6), genitourinary symptoms (aOR, 6.84; 95% CI, 3.18-15.0), and skin lesions (aOR, 2.39; 95% CI, 1.58-3.60) were independently associated with increased odds of MTZ prescription. In contrast, fever (aOR, 0.66; 95% CI, 0.49-0.87), respiratory symptoms (aOR, 0.44; 95% CI, 0.26-0.71), and malaria (aOR, 0.21; 95% CI, 0.15-0.28) were associated with decreased odds. Visits in the private sector were also associated with higher odds of MTZ prescription compared with the public sector (aOR, 2.31; 95% CI, 1.78-3.02). ConclusionMTZ is the second most commonly prescribed antibiotic in primary care in the study area, with its use largely driven by digestive symptoms. Further studies are needed to assess the appropriateness of this prescription. Additionally, research is warranted to understand better the determinants of higher antimicrobial prescribing in the private healthcare sector. Highlights- MTZ is the second most prescribed antibiotic in the study area. - MTZ prescription is primarily driven by digestive symptoms. - The private healthcare sector is independently associated with higher MTZ prescription rates. - Antimicrobial prescribing is generally higher in private healthcare facilities than in public facilities.

Urinary tract infection (UTI) is one of the most common community-acquired bacterial infections mainly caused by extraintestinal pathogenic Escherichia coli (ExPEC) strains. The high-risk Escherichia coli ST131 clone is a major global cause of this disease. The lineage rapid dissemination is associated to multidrug resistance (MDR), production of extended-spectrum beta-lactamase (ESBL), and multiple virulence-associated genes. Although we lack information about ExPEC high-risk clones in Latin America, we recently reported an increase in ST131 dissemination in Rio de Janeiro from 2015 to 2019. The present study aims to characterize virulence and resistance molecular and phenotypic features that may contribute to dissemination of E. coli ST131 in Rio de Janeiro, Brazil. We assessed a 133 E. coli ST131 strains collection obtained from urine of outpatients with suspected UTI, in 2019. We determined antimicrobial susceptibility, fluoroquinolones resistance genes, virulence factors associated genes and biofilm production of all strains and analyzed the frequencies by each clade or subclade. A higher incidence of women (92%) and elderly (65%) subjects was observed. Overall resistance to first- and second-line treatment for UTI antimicrobials ampicillin, ciprofloxacin and sulfamethoxazole-trimethoprim was detected in high rates (40%), with a major impact of subclade C2 strains that were resistant to almost all antimicrobials tested, 52% carry ESBL and 66% of strains harbor the aac(6)-Ib-cr ciprpofloxacin resistance gene. Clade B and subclade C2 showed higher virulence scores among the other clades. They present unique virulence profiles characterized by the presence of papGIII, sfa/focDE, and especially ibeA genes in clade B, and the afa/DrBC, papGII, hlyA, cnf1 genes in subclade C2. Over 50% of our strains are biofilm producers, characterized by weak (24%) and strong producers (32%). ESBL and MDR strains harbor mainly papA, papGII, hlyA, cnf1 and kpsMTII genes that plays a key role in ST131 colonization. Subclade C1 is the major biofilm producer (78%), despite its lower virulence score. We also detected higher incidence of papA (27%), hlyA (19%) genes and the RPAI(malX) marker (84%) in biofilm producer strains with a statistical association of sfa/focDE gene (9%). We can infer that Clade C strains might be responsible for ST131 dissemination and persistence in Rio de Janeiro.