Piquart L, Goutelle S, Maillard M
… +6 more, Boisset S, Carricajo A, Tristan A, Ranc AG, Laurent F, Dupieux C
J Antimicrob Chemother
· 2026 Mar · PMID 41878879
·
Full text
BACKGROUND AND OBJECTIVES: Bone and joint infections (BJIs) due to third-generation cephalosporin-resistant (3GC-R) Enterobacterales are particularly challenging-to-treat infections, and their treatment often relies on c...BACKGROUND AND OBJECTIVES: Bone and joint infections (BJIs) due to third-generation cephalosporin-resistant (3GC-R) Enterobacterales are particularly challenging-to-treat infections, and their treatment often relies on carbapenems. Due to its stability towards various beta-lactamases, as well as its limited spectrum of activity, temocillin could be a promising alternative. This study evaluated the in vitro activity of temocillin against a collection of 3GC-R Enterobacterales isolates from BJIs and modelled the probability of PK/PD target attainment according to the dosage regimen used. METHODS: MICs of temocillin and seven comparators (ertapenem, imipenem, meropenem, levofloxacin, delafloxacin, doxycycline and tigecycline) were determined using gradient strips for 104 3GC-R Enterobacterales isolates from BJIs in three French hospitals. Isolates were characterized about their mechanism of resistance to 3GC (ESBL or hyperproduced cephalosporinase). PK/PD simulations were performed with six dosage regimens and different stages of renal function in order to calculate PTA according to temocillin MIC. RESULTS: Temocillin showed a susceptibility rate of 92.3% (96/104) in 3GC-R isolates from BJIs: 95.3% (61/64) in ESBL producers and 87.5% (35/40) in AmpC hyperproducers. Temocillin was the only alternative to carbapenems for 25% (26/104) of isolates. PTA values increased with declining renal function. In normorenal patients, none of the tested regimen achieved adequate PTA up to the Enterobacterales breakpoint (16 mg/L). CONCLUSIONS: This study demonstrated the high in vitro efficacy of temocillin against 3GC-R Enterobacterales from BJIs, regardless of the underlying resistance mechanism. However, dosage adjustments based on the strain's MIC and the patient's renal function are crucial for optimal efficacy.
van den Berg S, Attwood M, Griffin P
… +11 more, Noel A, Das S, Zeitlinger M, Racine E, Boulenc X, Muller AE, Sassen SDT, Bahmany S, Ten Kate MT, MacGowan A, Meletiadis J
J Antimicrob Chemother
· 2026 Mar · PMID 41873441
·
Full text
BACKGROUND: NOSO-5O2 is the first clinical candidate of a new antimicrobial class, the odilorhabdins. The pharmacodynamics of NOSO-502 was studied to establish the magnitude of the pharmacodynamic index (PDI) and make hu...BACKGROUND: NOSO-5O2 is the first clinical candidate of a new antimicrobial class, the odilorhabdins. The pharmacodynamics of NOSO-502 was studied to establish the magnitude of the pharmacodynamic index (PDI) and make human dose predictions. METHODS: In vitro experiments using different types of media were performed in time-kill curves and a pharmacokinetic model. In vivo experiments were conducted in the neutropenic murine thigh infection model. Six E. coli (MIC 1-8 mg/L) and two K. pneumoniae (MIC 1-2 mg/L) strains were used. 24 h bacteriostatic and 1- and 2-log10 kill effects were related to fAUC0-24/MIC and fAUC0-24/MIC per length of dosing interval (fAUC0-24/MIC·1/tau). Human pharmacokinetic parameters were predicted using interspecies allometric scaling and used to simulate the dose needed to reach the bacteriostatic PDI target for E. coli. RESULTS: The in vitro activity of NOSO-502 was dependent on the media and the strength of Mueller-Hinton Broth II (MHBII) used such that fAUC0-24/MIC ratios were higher when measured in 100% MHBII than 50% MHBII. In vivo for E. coli, the fAUC0-24/MIC for bacteriostatic effect and 1-log10 reduction in bacterial count were 10.7 ± 10.9 and 18.2 ± 16.5, respectively. The final human predicted parameters of the model had CV values of <20%. The human dose required to achieve the bacteriostatic fAUC0-24/MIC for each E. coli strain varied from 149 to 1717 mg/day. CONCLUSIONS: A combination of the use of PDI targets and prediction of human pharmacokinetics allowed effective doses of NOSO-502 in man to be estimated.
Inciarte A, Berrocal L, Santos JR
… +12 more, Aleman MR, Curran A, Medina Gonzalez R, Bernal S, de Lazzari E, Garcia Del Toro M, Raventós B, Lopez Lirola AM, Martínez E, Paredes R, Blanco JL, Integrasa Marginal Study Group Team Group
OBJECTIVES: To assess the prevalence of transmitted drug resistance mutations (TDRMs) and the impact of pre-existing resistance mutations, including minority variants, on virological response in ART-naïve individuals ini...OBJECTIVES: To assess the prevalence of transmitted drug resistance mutations (TDRMs) and the impact of pre-existing resistance mutations, including minority variants, on virological response in ART-naïve individuals initiating dolutegravir-based triple therapy using next-generation sequencing (GRT-NGS). METHODS: A multicentre, retrospective cohort study was conducted including ART-naïve individuals who started a dolutegravir-3DR between 2015 and 2019. Baseline GRT-NGS Illumina®, covering RT, PR and IN genes identified primary (P-DRM) and secondary/polymorphic (S/p-DRM) mutations in high-abundance drug resistance variants (HA-DRVs; ≥20%) and low-abundance drug resistance variants (LA-DRVs; 1%-19%). Virological failure (VF) was defined as two consecutive HIV-1 RNA ≥ 50 copies/mL. Virological response was assessed at Weeks 48 and 96. RESULTS: Of 326 participants, 86% were male and 72% were MSM; 78% received DTG/ABC/3TC and 22% TDF/FTC + DTG. At least one TDRM was detected in 24% and any DRM in 48% of subjects. Virological suppression was achieved in 76% by intention-to-treat (ITT), 97% on-treatment (OT) and 56% (ITT), 94% (ITT) at Weeks 48 and 96, respectively. VF occurred in 11 subjects (3.4%), mostly within 48 weeks, all with low-level viraemia (<1000 copies/mL; 8 < 200 copies/mL) and no emergent of new DRM in HA-DRVs with phenotypic impact. Among those with pre-existing DRM, including 36 P-HA-DRVs, 79 S/p-HA-DRVs, 57 P-LA-DRVs and 45 S/P-LA-DRVs, no significant association with VF was observed. CONCLUSIONS: Our findings indicate that pre-existing IN and RT DRM, including low-abundance and secondary/polymorphic variants, did not compromise the virological efficacy of dolutegravir-based triple therapy in ART-naïve individuals, supporting the high resistance barrier of dolutegravir and the lack of need for baseline resistance testing.
J Antimicrob Chemother
· 2026 Mar · PMID 41873439
·
Full text
BACKGROUND: The female genital tract (FGT) is a unique compartment with physiologically distinct properties complicating the extrapolation of drug efficacy; critical gaps remain in understanding regional variability with...BACKGROUND: The female genital tract (FGT) is a unique compartment with physiologically distinct properties complicating the extrapolation of drug efficacy; critical gaps remain in understanding regional variability within the FGT itself. We performed an in-depth investigation across endo- and ectocervical tissues on the utility of the cervical explant model to evaluate pre-exposure prophylaxis (PrEP) efficacy. METHODS: Using normal cervical tissues, we evaluated gene expression of relevant drug metabolizing enzymes and transporters (DMETs) via qRT-PCR and compared ecto- and endocervix. To determine differences in drug phosphorylation and to assess antiretroviral (ARV) efficacy, we incubated explants in tenofovir and emtricitabine then measured intracellular metabolites. Viral infectivity and dose-response with ARVs was measured using viral RNA and p24 following HIV-1JR-CSF challenge. RESULTS: ABCC4 expression was 3-fold lower in ectocervical tissues compared with endocervical, whereas CYP3A5 was 2-fold higher. IL-6 was correlated with ABCB1 (r = 0.52, P = 0.01) and ABCG2 (r = 0.56, P =0.005). Dose-normalized phosphorylation did not differ between endo- and ectocervix (P > 0.5). Infectivity of explants was low (53%) but did not differ by compartment. Intracellular tenofovir diphosphate concentrations were associated with a decrease in ectocervical viral replication (r =0.39, P < 0.05). There was a strong relationship between the proportion of explants infected and emtricitabine dose (P =0.02) but no relationship between intracellular emtricitabine triphosphate and protection. CONCLUSIONS: We identified differences in DMET expression and ARV metabolism between ecto- and endocervical tissues, as well as correlations between DMET and IL-6. Ectocervical explants demonstrated consistent viral infectivity and dose-dependent inhibition. The model is useful in determining tenofovir diphosphate targets.
Han N, Loosli T, Sauermann M
… +29 more, Çelikağ İ, Anderegg N, Baye BC, Bolton Moore C, Buzaalirwa L, Byakwaga H, Chimbetete C, Ebasone PV, Goodrich S, Huwa J, Kasozi C, Mafoua A, Massamba AC, Messou E, Minga A, Murenzi G, Muula G, Muyindike W, Naidoo SJ, Nsonde DM, Poda AG, Ramdé R, Semeere A, Singh L, Günthard HF, Egger M, Giandhari J, Lessells R, Kouyos RD
J Antimicrob Chemother
· 2026 Mar · PMID 41873438
·
Full text
BACKGROUND: Integrase mutations associated with dolutegravir resistance have been well characterized, but based on limited data from non-B subtypes. OBJECTIVES: We aim to identify potential integrase mutations not curren...BACKGROUND: Integrase mutations associated with dolutegravir resistance have been well characterized, but based on limited data from non-B subtypes. OBJECTIVES: We aim to identify potential integrase mutations not currently classified as integrase strand transfer inhibitor (INSTI) resistance mutations (DRMs) in individuals with viremia on dolutegravir-based regimens. METHODS: We included integrase sequences from DTG RESIST study sites in African countries. These were interpreted using Stanford HIVdb v9.8. We used a viral genome-wide association study-like approach restricted to the integrase region (INT-WAS) to identify mutations not classified as major or accessory INSTI DRMs but occurring more frequently in sequences carrying major INSTI DRMs than in those without major INSTI DRMs. We performed the same INT-WAS analysis with drug-naïve sequences from the Los Alamos HIV-1 database to test whether these identified mutations were enriched among sequences from individuals with viraemia whilst receiving DTG-based treatment. RESULTS: Among 382 sequences, 104 (27.2%) showed at least intermediate dolutegravir resistance. Twelve integrase mutations not classified as major or accessory DRMs (S39R, L45I, I72L, L74I, V79I, I113V, S119R, K156N, I208M, T218M, A265V, and R284G) were significantly associated with predicted DTG resistance. Among them, V79I [adjusted odds ratio (aOR) 167.1, 95% credible interval (CrI) 17.9-2947.6] and I72L (aOR 65.6, 95% CrI 6.6-1273.7) were strongly associated. S39R, L45I, V79I, S119R, and K156N were linked to established INSTI resistance pathways, and I72L, L74I, V79I, K156N, I208M, and R284G were overrepresented in sequences from viraemic individuals on DTG-based treatment relative to drug-naïve sequences. CONCLUSIONS: We identified several amino acid substitutions outside the established DRMs that are strongly associated with predicted dolutegravir resistance. Dolutegravir resistance evolution is complex and likely involves mutations not currently classified as DRMs.
BACKGROUND: The plasmid-mediated tigecycline resistance gene tmexCD-toprJ has emerged in clinical and animal isolates, but its epidemiological spread and plasmid adaptation mechanisms remain unclear. METHODS: We characte...BACKGROUND: The plasmid-mediated tigecycline resistance gene tmexCD-toprJ has emerged in clinical and animal isolates, but its epidemiological spread and plasmid adaptation mechanisms remain unclear. METHODS: We characterized tmexCD-toprJ-carrying plasmids from the PLSDB database through comprehensive bioinformatic analyses, revealing their genetic features and potential inter-species transmission routes. RESULTS: Genomic analysis of 197 tmexCD-toprJ-carrying plasmids revealed significant backbone diversity, clustering into 18 groups and 12 singletons. The 30 identified host species were predominantly Klebsiella pneumoniae (K. pneumoniae) (53.3%), followed by Pseudomonas aeruginosa (P. aeruginosa) (16.8%) and Klebsiella quasipneumoniae (K. quasipneumoniae) (4.1%). MOB-suite typing classified 53.8% as conjugative, 5.6% mobilizable and 40.61% non-mobilizable. Over half of the tmexCD-toprJ-carrying plasmids were predicted to contain the MOBH family. Among the identified variants, tmexCD1-toprJ1, tmexCD2-toprJ2 and tmexCD3-toprJ1 representing the predominant forms. TmexCD1-toprJ1 was linked to IncFIB/IncHI1B/rep_cluster_1254 plasmids, while tmexCD2-toprJ2 associated with diverse replicons, enabling cross-species spread. A total of 14 plasmids co-localized tmexCD-toprJ with carbapenemase (blaNDM/KPC) and mcr genes, forming high-risk resistance platforms. Notably, a 36 483 bp insertion in IncP/rep_cluster_1115 plasmids disrupted tmexC6D6-toprJ1b and carried heavy metal resistance genes. CONCLUSIONS: These findings enhance our understanding of the diversity of tmexCD-toprJ-carrying plasmids. The convergence of tmexCD-toprJ with carbapenemase and polymyxin resistance genes in clinically prevalent plasmids underscores an urgent need for enhanced surveillance targeting complete genetic environments.
Continuous infusion (CI) of linezolid has been proposed to stabilize exposure and improve pharmacokinetic/pharmacodynamic (PK/PD) target attainment compared with conventional intermittent dosing. By maintaining concentra...Continuous infusion (CI) of linezolid has been proposed to stabilize exposure and improve pharmacokinetic/pharmacodynamic (PK/PD) target attainment compared with conventional intermittent dosing. By maintaining concentrations above inhibitory thresholds, CI may optimize antibacterial efficacy and reduce inter- and intra-patient variability. However, this 'new way of dosing' revisits 'old risks' associated with linezolid, including nonlinear PK, metabolic saturation, and concentration-dependent toxicities such as lactic acidosis, myelosuppression and neurotoxicity. Rather than eliminating these concerns, CI may accentuate them by prolonging exposure near toxic thresholds, particularly in patients with impaired elimination. Current evidence is predominantly PK; robust clinical outcome data remain limited. Our review synthesizes pharmacometric, observational and trial data and outlines how therapeutic drug monitoring and model-informed precision dosing can be used to individualize CI while surveilling for toxicity. We propose a pragmatic framework for candidate selection, regimen design aligned to PK/PD goals, early therapeutic drug monitoring with adaptive adjustments and vigilant safety monitoring. Overall, CI of linezolid is mechanistically attractive but is not established as standard of care; its use should remain individualized, safety-conscious and evidence-generating pending randomized controlled trials.
van den Berg S, Pieren M, Sassen SDT
… +4 more, de Jong WAM, Boonman CSC, Dale GE, Muller AE
J Antimicrob Chemother
· 2026 Mar · PMID 41843493
·
Full text
OBJECTIVES: Polymyxin B has been used for many years to treat Acinetobacter baumannii, but little is known about its pharmacodynamics (PD). We aimed to describe the PD of polymyxin B in treating A. baumannii infections....OBJECTIVES: Polymyxin B has been used for many years to treat Acinetobacter baumannii, but little is known about its pharmacodynamics (PD). We aimed to describe the PD of polymyxin B in treating A. baumannii infections. METHODS: Using the murine neutropenic thigh and lung infection models we determined the magnitude of the pharmacokinetic (PK)/PD index correlating with efficacy for eight A. baumannii strains. PD was analysed using the Emax model to determine PD targets. Using published human PK data the PTAs were calculated. RESULTS: In the thigh infection model, stasis, 1-log10 and 2-log10 kill were reached for all strains. Median (range) fAUC/MIC (area under the unbound concentration-time curve divided by the MIC) targets for stasis, 1-log10 kill and 2-log10 kill were 2.1 (1.0-11), 2.9 (1.0-15) and 4.0 (1.1-20), respectively. In contrast, in the lung model, 2-log10 kill was reached in 2/8 strains only, and there was insufficient killing at tolerated exposures to determine PD fAUC/MIC targets. For the standard human dosing regimen, PTAs derived from the thigh model were inadequate at the USCAST (United States Committee on Antimicrobial Susceptibility Testing) clinical breakpoint and a protein binding of 90%. CONCLUSIONS: Whereas polymyxin B treatment had good efficacy in the murine thigh infection model, in the lung infection model its effect was limited. PD targets, with MICs of circulating A. baumannii isolates of ≤2 mg/L, are not reached with a standard human dosing regimen and will probably exceed threshold values for toxicity. These data suggest that the efficacy of polymyxin B as monotherapy for A. baumannii infections is questionable.
J Antimicrob Chemother
· 2026 Mar · PMID 41841430
·
Full text
OBJECTIVES: Acquired resistance to last-line linezolid has emerged in Enterococcus spp. and can be conferred by the optrA gene. Here, we study the global genomic context of optrA in E. faecalis and E. faecium, to underst...OBJECTIVES: Acquired resistance to last-line linezolid has emerged in Enterococcus spp. and can be conferred by the optrA gene. Here, we study the global genomic context of optrA in E. faecalis and E. faecium, to understand its dissemination pattern. METHODS: We identified 565 enterococcal genomes from NCBI and 86 optrA-containing enterococcal plasmids from the plasmid database, PLSDB. We characterized the plasmid replication and antimicrobial resistance genes of optrA-containing plasmids and the plasmid pangenome. To identify prevalent optrA genetic contexts, we mapped the genomes against PLSDB plasmid and transposon Tn6674 (prevalent in E. faecalis) sequences using minimap2. RESULTS: A greater proportion of E. faecium (47.3%: n = 70/149) carried the optrA gene on plasmids than E. faecalis (28.9%: n = 120/416). In E. faecalis, the major optrA contexts were represented either by a Tn6674 transposon (28.0%) or a plasmid-associated MDR fexA-optrA-erm(A) genetic unit (32.9%), and were associated with distinct E. faecalis phylogroups. In E. faecium, the dominant optrA contexts were the optrA-erm(A)/(B) genetic unit (24.2%), the fexA-optrA-erm(A) unit (16.8%), and the Tn6261 transposon (14.1%). We observed that in some E. faecalis and E. faecium plasmids, the fexA-optrA-erm(A) unit was flanked by IS1216E elements on both sides, suggesting the mobilization of this MDR gene cassette by IS1216E-like elements into diverse plasmid backgrounds. CONCLUSIONS: This is the first study to investigate the genomic context of optrA in a phylogeographically diverse enterococcal genome collection. We demonstrated that mobile genetic elements play a key role in the global expansion of optrA and highlighted the underlying public health concern imposed by plasmids in drug-resistant enterococcal dissemination.
Thomas A, Vogrin S, Batrouney A
… +7 more, Devchand M, Khumra S, Narayanasamy S, Motaganahalli S, Trubiano JA, Warrillow SJ, Reynolds GK
J Antimicrob Chemother
· 2026 Mar · PMID 41841429
·
Full text
OBJECTIVES: To evaluate the long-term sustainability and impact of an integrated electronic medical record-driven antimicrobial stewardship (AMS) ward round in an ICU at a tertiary referral hospital. The study assessed a...OBJECTIVES: To evaluate the long-term sustainability and impact of an integrated electronic medical record-driven antimicrobial stewardship (AMS) ward round in an ICU at a tertiary referral hospital. The study assessed antimicrobial prescribing patterns, acceptance of stewardship recommendations, and antimicrobial consumption over 7 years. METHODS: A prospective review commenced with implementation of the ICU-AMS ward round at Austin Health in 2017. When AMS recommendations were given, data were collected including patient demographics, antimicrobial prescribing, classification of recommendation, and acceptance. Antimicrobial use was assessed via DDDs per occupied bed day per month and analysed using interrupted time series analysis. Logistic regression examined patient and clinician factors associated with recommendation acceptance. RESULTS: Over 7 years, 9163 AMS recommendations were made for 4610 patients. Recommendation acceptance was high, with antibiotic escalation the most accepted (95%) and discontinuation least accepted (82%). Recommendations were more likely to be accepted in immunocompromised (OR 1.31, P = 0.003) and non-surgical patients (OR 1.31, P < 0.001). Recommendations provided by AMS physicians who identified as men were more likely to be accepted (OR 1.23, P = 0.003). Antimicrobial consumption trends showed significant decreases in piperacillin/tazobactam, meropenem, ciprofloxacin and vancomycin use post-implementation. Amoxicillin/clavulanate use increased, suggesting potential compensatory prescribing. CONCLUSIONS: This study demonstrates the long-term effectiveness and sustainability of an ICU-AMS programme, achieving high recommendation acceptance and sustained reductions in broad-spectrum antimicrobial use. Continued efforts should focus on optimizing stewardship practices, addressing barriers to acceptance, and evaluating compensatory prescribing patterns.
OBJECTIVES: Oral second- and third-generation cephalosporins are increasingly used as transitional therapy for Escherichia coli bloodstream infection, particularly in patients with resistance and intolerance to first-lin...OBJECTIVES: Oral second- and third-generation cephalosporins are increasingly used as transitional therapy for Escherichia coli bloodstream infection, particularly in patients with resistance and intolerance to first-line agents. However, many automated antimicrobial susceptibility testing (AST) systems only assess parenteral cephalosporins, potentially delaying transitions of care. Limited data exist on the correlation and surrogacy between parenteral and oral cephalosporin AST. We aimed to determine whether AST for parenteral cefazolin, ceftriaxone or cefotaxime can serve as surrogates to predict susceptibility for oral cephalosporins. METHODS: E. coli blood isolates susceptible to parenteral third-generation cephalosporins were consecutively collected from unique patients from two health systems in Phoenix, AZ, USA from January 2021 to 2023. Broth microdilution was performed according to CLSI. Categorical agreement (CA) rates were calculated using cefazolin, ceftriaxone, or cefotaxime as the surrogate antibiotic for oral cephalosporins (cefuroxime, cefaclor, cefprozil, cefdinir, cefpodoxime, cefixime). Discrepancies were classified as minor errors (mE), major errors (ME), or very major errors (VME) per CLSI. RESULTS: Among 200 isolates, susceptibility to cefazolin at MIC ≤2 mg/L, cefazolin at MIC ≤16 mg/L, ceftriaxone and cefotaxime at MIC ≤1 mg/L were 43%, 91.5% and 100%, respectively. Cefazolin MIC ≤2 mg/L provided high CA across oral cephalosporins but excessive mE (25%-37%) and ME (20%-40%) rates. Ceftriaxone and cefotaxime achieved 100% CA for oral third-generation cephalosporins with mE rates within acceptable limits; however, CA was suboptimal for oral second-generation agents (83%-88%). No surrogate antibiotic met acceptable CLSI criteria due to lack of CA, however, ceftriaxone/cefotaxime achieved acceptable limits in CA, mE, ME and VME. CONCLUSIONS: Prediction of oral second-generation cephalosporins may warrant cefazolin MIC ≤2 mg/L, despite limitations regarding false resistance and susceptibility discordant. Ceftriaxone/cefotaxime demonstrates a more reliable surrogate for predicting oral third-generation cephalosporins susceptibility. Future investigations are necessary to clinically corroborate these findings.
Damsté C, Stoorvogel H, Oerlemans A
… +4 more, Knippenberg M, van Gurp J, Ten Oever J, Hulscher M
J Antimicrob Chemother
· 2026 Mar · PMID 41834471
·
Full text
OBJECTIVES: Providing care to multi-drug resistant organisms (MDRO) carriers has a profound impact on healthcare providers (HCPs), potentially challenging their personal and professional values. Understanding HCPs' exper...OBJECTIVES: Providing care to multi-drug resistant organisms (MDRO) carriers has a profound impact on healthcare providers (HCPs), potentially challenging their personal and professional values. Understanding HCPs' experiences is key to addressing challenges in providing care to carriers and to support HCPs when providing this care. This review aims to examine experiences of HCPs with a focus on moral dimensions of care. METHODS: We systematically searched Cochrane library, CINAHL, EMBASE, PsycINFO, PubMed and Web of Science. Experiences were analysed using a thematic analysis approach. This review was registered in PROSPERO (CRD42023418340). RESULTS: Eighteen studies were included, primarily conducted in hospitals and nursing homes. Experiences were categorized into three levels: the individual HCP, the care practice and the institutional setting. First, HCPs are uncertain about personal health and safety, have different knowledge levels and question proportionality of infection prevention and control (IPC) measures. Second, HCPs say that wearing PPE limits connection with carriers and note various other challenges regarding the care relationship such as considering how often to enter an isolation room. Third, HCPs face shortages in resources such as time, experience poor infrastructure making it difficult to adhere to IPC measures and specify a need for management support regarding caring for carriers. Moral dimensions of care received limited attention. An example is that HCPs do not want to betray colleagues who ignore IPC measures, but simultaneously fear transmission due to poor compliance. CONCLUSIONS: The diverse experiences provide input for future interventions to support HCPs in caring for MDRO carriers. The limited attention to moral dimensions of care restricts understanding of HCPs' values and challenges. Strengthening support requires further research, particularly qualitative studies led by ethics experts.
OBJECTIVES: This study aims to elucidate the molecular mechanism of enhanced florfenicol resistance mediated by the resistance-enhanced RE-CmeABC in Campylobacter, with a focus on the evolution of its efflux function. MA...OBJECTIVES: This study aims to elucidate the molecular mechanism of enhanced florfenicol resistance mediated by the resistance-enhanced RE-CmeABC in Campylobacter, with a focus on the evolution of its efflux function. MATERIALS AND METHODS: The complex models of FFC with wild-type CmeB and RE-CmeB are constructed by molecular modelling methods, and the efflux channels and corresponding bottleneck residues are predicted by CAVER program. Then mutants are constructed on the basis of predicted amino acid residues by natural transformation and functional confirmation is performed by antimicrobial susceptibility testing and accumulation assay. RESULTS: Channel P1 is identified as the optimal FFC efflux channel, and the specific residues composed are illustrated. The corresponding bottleneck residues are S615, S616, Q87, T614, K89, S47 and S84. Among them, mutations of Q87 and K89 are non-conserved, having a particularly pronounced effect on efflux function. Decreased (8-fold) MIC and increased FFC accumulation were observed in MU-11168-RE-CmeABC (with mutated RE-CmeB) compared with that in 11168-RE-CmeABC (with RE-CmeB), respectively, which verifies the predicted FFC efflux tunnel is reliable. This demonstrates that the P1 channel in RE-CmeB has evolved into a dominant and specialized extrusion pathway with minimal functional redundancy, fundamentally underpinning its enhanced resistance. CONCLUSIONS: Our findings reveal that the enhanced resistance is primarily due to a functional specialization of the P1 efflux channel in RE-CmeB. This elucidation, strongly supported by the concordance between computational predictions and experimental data, provides a mechanistic basis and high-value targets (Q87/K89) for the development of efflux pump inhibitors against multidrug-resistant Campylobacter.
OBJECTIVES: To search for colistin heteroresistance (CHR) prevalence in Acinetobacter baumannii bloodstream isolates, and to investigate potential molecular contributors to CHR using WGS. METHODS: A total of 267 A. bauma...OBJECTIVES: To search for colistin heteroresistance (CHR) prevalence in Acinetobacter baumannii bloodstream isolates, and to investigate potential molecular contributors to CHR using WGS. METHODS: A total of 267 A. baumannii isolates were recovered from bloodstream infections between January 2014 and July 2018 at a tertiary care hospital in Türkiye. Antimicrobial susceptibility to colistin was assessed using the broth microdilution method. CHR was evaluated by population analysis profiling (PAP). WGS was performed on a representative heteroresistant strain (A325) to investigate putative CHR-associated mechanisms. RESULTS: Thirty-five isolates (13.9%) were classified as colistin-resistant. CHR was identified in 86 of 267 isolates (32.2%) using PAP. Comparative genomic analysis of the colistin-susceptible main population and the colistin-resistant subpopulation of isolate A325 revealed identical mutational profiles in known resistance-associated genes, with the exception of a partial deletion in the lpxD gene between codons 2 and 75, identified exclusively in the resistant subpopulation. Notably, tetracyclines, macrolides and aminoglycosides were fully inactive in the colistin-susceptible main population, whereas an inhibition zone around these antibiotic discs was observed with the colistin-resistant subpopulation. CONCLUSIONS: This study demonstrates a high prevalence of both colistin resistance and CHR among A. baumannii bloodstream isolates. The identification of a partial lpxD deletion in the resistant subpopulation of the colistin-heteroresistant isolate suggests a potential contributory role of LPS-related alterations in CHR. Inverse antimicrobial activity profiles between populations highlight distinct resistance mechanisms potentially shaped by evolutionary trade-offs and collateral sensitivity.