Invasive non-typhoidal Salmonella (iNTS) infections impose a huge disease burden on developing countries, and antimicrobial resistance is growing rapidly. However, systematic data on iNTS resistance remain scarce, limiting effective vaccine design and clinical strategies. This meta-analysis was performed to estimate the antibiotic resistance prevalence of iNTS and support targeted interventions and vaccine development. PubMed, Embase, Web of Science, Scopus, Cochrane, CNKI, WanFang, and VIP databases were searched for eligible studies published in English between 2000 and 2026. Only studies reporting antibiotic resistance in iNTS were included. Antibiotic resistance was confirmed by samples collected from sterile sites. Resistance rates of iNTS to eight antibiotics (ampicillin, ceftriaxone, etc.) were extracted to investigate the prevalence and temporal trends of iNTS in developing countries. A random-effects model was used for data synthesis to account for heterogeneity, and various statistical analyses were conducted using R and the metafor package. Forty-five studies comprising 11 447 individuals from 19 developing countries were included. The meta-analysis demonstrated substantial resistance of iNTS to multiple antibiotic classes. The highest resistance rates were observed for ampicillin (50.5%) and trimethoprim-sulfamethoxazole (39.4%), followed by chloramphenicol (28.9%), tetracycline (21.5%), and gentamicin (14.9%). Resistance was also detected to ceftriaxone (5.7%), a key first-line treatment for iNTS infections, and ciprofloxacin (5.9%), a commonly prescribed fluoroquinolone. Overall, the pooled prevalence of multidrug resistance was 41.1%, highlighting the substantial burden of antimicrobial resistance among iNTS isolates. This study systematically reviewed the antimicrobial resistance characteristics of iNTS in developing countries, identified regional and methodological differences, and suggested standardized detection and region-targeted interventions to combat antimicrobial resistance.
Ensuring the reliability, standardization, and international comparability of antimicrobial resistance (AMR) surveillance data critically depends on the implementation of robust quality assurance frameworks. South Korea established the Korea Global Antimicrobial Resistance Surveillance System (Kor-GLASS), supported by a centralized quality control center (QCC). As Kor-GLASS transitioned from Phase II to Phase III, new bacterial species and antimicrobial agents were incorporated, underscoring the need to evaluate whether quality assurance performance could be sustained during system expansion. We analyzed interlaboratory proficiency testing (IPT) and external quality assessment (EQA) outcomes generated by the QCC between 2020 and 2024, covering Phases II and III of Kor-GLASS. Clinical isolates were collected at participating hospitals and transferred to organism-specialized analysis centers for standardized antimicrobial susceptibility testing (AST), while the QCC independently oversees data quality through IPT and EQA. IPT was conducted by comparing AST results between analysis centers and the QCC using subsets of routine clinical isolates, with acceptance criteria defined as categorical agreement (CA) ≥90% and major error rates <3%. EQA involved quarterly distribution of pre-characterized strains to participating centers. Additional evaluations addressed the performance of newly introduced ceftazidime-avibactam susceptibility testing and interlaboratory validation for Haemophilus spp. Across the study period, overall CA consistently exceeded 97% in IPT, and no EQA failures observed among participating centers. While major errors during Phase II were primarily attributable to AST reading and near-breakpoint discrepancies, their frequency markedly decreased in Phase III following targeted corrective actions and educational interventions. Susceptibility testing for ceftazidime-avibactam showed high concordance between centers, with rare discrepancies limited to near-breakpoint measurements. Interlaboratory validation confirmed acceptable performance for AST of Haemophilus spp., supporting its formal inclusion in Phase III. These findings demonstrate that a centralized, QCC-led quality assurance framework can maintain stable and reliable AMR surveillance performance during periods of system expansion. Beyond routine oversight, coordinated quality assurance activities function as an evidence-based evaluation of how standardized laboratory data are generated and validated, reinforcing their essential role in sustaining the credibility and future development of AMR surveillance systems.
The spread of antimicrobial resistance (AMR) in Escherichia coli is driven by the acquisition of antibiotic resistance genes (ARGs) via mobile genetic elements in animal and environmental reservoirs. This study aimed to characterize the resistome, mobilome, and their associations in E. coli isolates from water buffaloes in southern Italy, evaluating their contribution to AMR dissemination. Thirty E. coli isolates were collected from water buffaloes on 16 farms in the Campania region between 2016 and 2023. Whole-genome sequencing was performed, and assemblies were analysed to determine sequence types (STs), serotypes, virulence factors, mobile genetic elements, and ARGs using bioinformatic tools. Statistical analyses were applied to assess associations between resistance gene and isolation data. Genomic analysis identified 18 STs, with ST10, ST29, and ST58 most frequent. The mobilome included 155 plasmids, 1175 prophages, 29 integrons, and over 700 insertion sequences, reflecting high genomic plasticity. A total of 87 ARGs, conferring resistance to β-lactams, aminoglycosides, tetracyclines, and sulphonamides, were detected, and all isolates were multidrug-resistant. About 30% of resistance genes were linked to plasmids or integrons. Significant associations between specific ARGs and farm or sampling year suggest environmental and temporal influences. E. coli from water buffaloes in Campania harbour a complex resistome and mobilome, supporting their role as reservoirs of AMR. The co-localization of multiple resistance genes on mobile elements highlights the risk of interspecies and zoonotic transmission, emphasizing the need for genomic surveillance within a One Health framework.
Carbapenem-resistant Citrobacter freundii (CRCF) has emerged as a growing global health concern, as it is increasingly implicated in human infections and recognized as an important reservoir of clinically significant antimicrobial resistance determinants. Although C. freundii carrying single carbapenemase genes has been widely reported, systematic global analyses of isolates harboring multiple carbapenemase genes remain limited. Citrobacter spp. isolates were recovered and antimicrobial susceptibility testing was determined using the broth microdilution method. We further conducted a comprehensive genomic analysis of multi-carbapenem-producing C. freundii (MCP-CF). Whole-genome sequencing data were used to characterize the carbapenemase gene profiles, multi-locus sequence types (MLST), phylogenetic relationships, geographic distribution, and plasmid replicon compositions. Through antimicrobial susceptibility testing, all MCP-CF isolates exhibited extensive resistance to β-lactams, with partial resistance to tigecycline but retained susceptibility to colistin. From the global perspective, MCP-CF isolates occurred at a low frequency but spanned multiple sequence types and geographic regions. Carbapenemase gene combinations predominantly comprised blaKPC and blaNDM and were associated with plasmids of heterogeneous replicon backgrounds. Phylogenetic analysis indicated that these isolates were phylogenetically dispersed rather than clonally related. Our findings demonstrate the capacity of C. freundii to acquire and disseminate multiple carbapenemase genes and reveal the widespread, yet under-recognized, distribution of these highly resistant strains. Continuous genomic surveillance and integrated analyses of public genomic data are essential for improving early detection and informing effective infection control and antimicrobial stewardship strategies.
Antimicrobial resistance (AMR) is a global public health threat, responsible for an estimated 35 200 bacterial resistance attributable deaths in the UK in 2019. Social determinants of health (SDoH) drive inequities that influence health outcomes. We aimed to conduct a scoping review of the evidence of the association between the SDoH and AMR in the UK. A scoping review was conducted using search terms related to SDoH and AMR across multiple databases, supplemented by manual searches. This followed Arksey and O'Malley's framework and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guideline. A systematic search was conducted across SCOPUS, PubMed, Academic Search Premier, AMED, APA PsycArticles, APA PsycInfo, CINAHL Plus with Full Text, Humanities International and Web of Science. Primary UK-based literature exploring SDoH in relation to infectious disease syndromes requiring antimicrobial therapy and reporting AMR were included. Studies from January 2020 onwards, published in English, across all populations were considered. Non-UK studies, reviews, studies not addressing AMR, laboratory-based research and non-human health contexts were excluded. Records were screened against eligibility criteria with reasons for exclusion documented. Data were charted against a customised form capturing study characteristics and key findings. Findings were thematically categorised to generate narrative synthesis. 21 outputs met the inclusion criteria. Older females and those from lower socioeconomic groups showed higher antibiotic use and resistance. Migrant populations were vulnerable to AMR through poor living conditions and limited healthcare access. Misconceptions about AMR were common among younger and socioeconomically disadvantaged populations. Prescribing practices reflected patient expectations, systemic pressures and healthcare gaps, while fragmentation between primary and secondary care limited coordinated management and policy implementation. AMR in the UK is driven by social, economic and systemic factors, placing vulnerable groups at heightened risk. Sustainable and equitable control requires integrating SDoH through targeted interventions, public engagement and inclusive policymaking to meet national and global targets.
Antimicrobial resistance (AMR) in pathogens causing bovine respiratory disease (BRD) is promoted by the prophylactic use of antimicrobials in calves. However, the impact of discontinuing their use under field conditions remains unclear. This study evaluated changes in antimicrobial susceptibility of Mannheimia haemolytica and Pasteurella multocida following cessation of prophylactic oxytetracycline and tilmicosin on a contract-rearing farm for Holstein heifer calves in Japan. Oxytetracycline was administered via milk replacer at 20 mg/kg/day to calves aged 6-60 days of age and discontinued in April 2022, whereas prophylactic tilmicosin (10 mg/kg, single subcutaneous injection at arrival) was discontinued in May 2023. From November 2021 to November 2023, 850 nasal and ear swab samples were collected from 583 calves with suspected BRD, yielding 492 M. haemolytica and 215 P. multocida isolates. These isolates underwent antimicrobial susceptibility testing and screening for oxytetracycline resistance genes. Over 1 year post-oxytetracycline withdrawal, minimum inhibitory concentration (MIC) distributions for oxytetracycline indicated a significant shift toward susceptibility in both species; resistance to oxytetracycline declined from 9.2% to 0% in M. haemolytica and from 75.0% to 5.6% in P. multocida. The MICs of florfenicol and macrolides (tilmicosin and tulathromycin) decreased with time. Most tetracycline-resistant isolates carried tet(H). After oxytetracycline discontinuation, the BRD incidence increased and average daily gain decreased; however, both improved following the introduction of an inactivated trivalent BRD vaccine. Discontinuing long-term prophylactic antimicrobial administration can restore antimicrobial susceptibility in BRD pathogens and aid in preserving therapeutic antimicrobial effectiveness when implemented alongside vaccination strategies.
To investigate how two major ciprofloxacin metabolites, 2-oxo ciprofloxacin (M3) and N-formyl ciprofloxacin (M4), influence the resistance profiles and biofilm characteristics of Pseudomonas aeruginosa (PAO1) and Staphylococcus aureus (ATCC 25923). Both metabolites were synthesised, structurally validated, and co-cultured with bacterial strains at sub-inhibitory concentrations (SICs) over a 30-day period. Minimum inhibitory concentration (MIC) assays, crystal violet biofilm quantification, and genomic and transcriptomic analyses (whole genome and differential RNA sequencing) were employed to assess phenotypic and molecular adaptations. Exposure to ciprofloxacin metabolites altered bacterial behaviour despite their weak intrinsic antimicrobial activity. In S. aureus, continuous exposure to M3 and M4 resulted in an eight and four-fold increase, respectively, in ciprofloxacin MIC values. In P. aeruginosa, although MIC values remained unchanged, prolonged exposure to both metabolites enhanced biofilm formation, M4 (p<0.0001) and M3 (p<0.0089)). Genomic sequencing of P. aeruginosa revealed a missense mutation (A290D) in the wspA gene following M3 exposure, which activates biofilm-promoting pathways via cyclic-di-GMP signalling. RNA sequencing identified 220 differentially expressed genes, including upregulation of quorum sensing regulators (rhlI, pqsH), nitric oxide cycle genes (nir, norCB), and the pel operon. Ciprofloxacin metabolites, though less potent than the parent antibiotic, can drive adaptive responses linked to resistance and persistence. Their capacity to induce stable genetic and transcriptomic shifts underscores their potential ecological and clinical significance as underexplored factors in AMR.
This study aimed to characterize the mobile genetic context of an ∼ 82 kb chromosomal region showing co-localization of heavy-metal and an antibiotic resistance island in an extensively drug-resistant (XDR) Enterobacter cloacae NH77. Genomic DNA was sequenced using the Pacific Biosciences RS II platform. Long reads were de novo assembled with Canu v1.4 and annotated using Prokka v1.12b. The complete genome was analyzed to identify sequence type, antimicrobial resistance genes, integrons, insertion sequences, and plasmid type using MLST 2.0, ResFinder 4.7.2, Comprehensive Antibiotic Resistance Database (CARD) 4.0.1, INTEGRALL, and PlasmidFinder 2.1. Comparative analyses were performed using BLAST against Enterobacteriaceae genomes available in the NCBI GenBank database. E. cloacae NH77 belonged to ST995 and was classified as XDR. The genome consisted of a 5 040 532 bp chromosome and a 41 179 bp IncN2 plasmid carrying blaNDM-1. A 49 286 bp chromosomal resistance gene island (RGI) contained two class 1 integrons (In191 and In705) associated with 15 antimicrobial resistance genes. BLAST analysis showed the high similarity of the ∼49 kb RGI to sequences found in the chromosomes of Enterobacter hormaechei and Enterobacter asburiae and Escherichia coli plasmid. The ∼49 kb RGI was located immediately downstream of a Tn7-sil-pco cluster, forming an ∼82 kb composite mobile resistance island. All sequences contained pcoSE located at the end of the ∼49 kb RGI. This study describes an XDR-E. cloacae ST995 clinical isolate containing an ∼82 kb chromosomal resistance island comprising Tn7-sil-pco and a ∼49 kb RGI. The mobile genetic context suggests that pcoSE may function as a recombination target site for the ∼49 kb RGI.
Pseudomonas aeruginosa is a major cause of healthcare-associated infections and a World Health Organization priority pathogen because of its marked ability to develop resistance to last-line antibiotics. Carbapenem resistance may arise through chromosomal mutations, acquisition of resistance genes, and clonal dissemination under sustained antimicrobial pressure. To investigate the temporal dynamics of carbapenem resistance in clinical P. aeruginosa isolates from a tertiary-care hospital in Valparaíso, Chile, and to assess their association with antimicrobial consumption. Forty-five clinical isolates recovered between 2019 and 2024 were analysed. Antimicrobial susceptibility testing, phenotypic and molecular carbapenemase detection, motility and biofilm assays, and whole-genome sequencing were performed. Sequence types, resistome, virulome, and chromosomal mutations associated with resistance were characterized. Antimicrobial consumption data from the local stewardship programme were evaluated using temporal trend and cross-correlation analyses. Carbapenem non-susceptibility was frequent, and extensively drug-resistant isolates predominated during the pandemic and post-pandemic periods. Resistance was mainly associated with non-carbapenemase-producing isolates and was linked to mutations in oprD, regulators of the MexAB-OprM efflux system, and ampC-related pathways, together with intrinsic OXA-50-like-β-lactamases. The blaVIM-2 gene was identified in ST408, ST815, and ST253. Temporal clonal turnover was observed, with ST309 emerging as the dominant lineage in 2023-2024. The acquired resistome diversified over time, whereas the virulome remained largely conserved. Higher antimicrobial consumption in intensive care units was associated with carbapenem resistance. Sustained antimicrobial pressure likely contributed to the persistence and replacement of carbapenem-resistant lineages. Integrating genomic surveillance with antimicrobial stewardship may improve detection and control of high-risk hospital clones.
Enterococcus faecium is a major cause of healthcare-associated infections and exhibits multidrug resistance. Fosfomycin, an older broad-spectrum antibiotic, has regained attention as a potential therapeutic option. However, reliable susceptibility testing remains challenging, and resistance rates and mechanisms in Taiwan are largely unexplored. A total of 377 E. faecium isolates from blood cultures collected in Taiwan between 2017 and 2022 were analyzed. Agar dilution was used to determine fosfomycin susceptibility, which was also assessed using the E-test and disc diffusion methods. Sequence types were identified by multilocus sequence typing. Potential resistance mechanisms were examined by detecting mutations in murA and pyk genes, upstream insertions in murAB, and the presence of acquired resistance determinants. Agar dilution identified 11 (2.9%) fosfomycin-resistant and 108 (29.0%) intermediate isolates. In contrast, the E-test and disc diffusion methods underestimated non-susceptibility rates (1.3% and 1.6%, respectively), primarily due to the misidentification of intermediate isolates as susceptible. Genotypic analysis of 14 fosfomycin-resistant or intermediate isolates revealed nine sequence types, with 85.7% belonging to clonal complex 17. Four MurA amino acid substitutions (A120T, I184V, R190L, and R263C) and two types of insertions upstream of murAB were detected, but none specifically correlated with resistance. All isolates tested negative for fosA, fosB, fosC, and fosX. Fosfomycin resistance among E. faecium isolates in Taiwan remains low; however, intermediate isolates are frequently underestimated by the E-test and disc diffusion methods. The genetic backgrounds of fosfomycin-non-susceptible strains appear diverse, and their resistance mechanisms remain to be elucidated.
Antibiotic-resistant Neisseria gonorrhoeae (Ng) is a WHO priority pathogen and represents a serious public health threat. This study reports the first Chilean Ng ST9363 isolate (GC11/23) exhibiting dual high-level resistance to azithromycin and fluoroquinolone, recovered from a urethral discharge sample in July 2023. Antimicrobial susceptibility was assessed using disk diffusion and MIC strip tests. Whole-genome sequencing (WGS) was performed using a hybrid approach, followed by annotation using the NCBI Prokaryotic Genome Annotation Pipeline (PGAP). In silico analyses included Staramr, MLST and NG-STAR. Phylogenetic analysis was performed on the core genome of 2417 global ST9363 Ng isolates using IQ-TREE and visualised with TreeViewer. GC11/23 exhibited resistance to ciprofloxacin, tetracycline, penicillin and azithromycin, while remaining susceptible only to ceftriaxone and spectinomycin. The isolate belonged to ST9363 and NG-STAR 3194. Mutations associated with fluoroquinolone resistance were identified in gyrA and parC, while high-level azithromycin resistance (HL-AziR) was linked to mutations in all four copies of the 23S rRNA gene, as well as in mtrD and mtrR. Additional resistance-associated alterations included an insertion (ins346D) in penA and a mutation in rpsJ, conferring resistance to penicillin and tetracycline, respectively. Phylogenetic analysis clustered GC11/23 with isolates from the USA and Europe collected in 2019. GC11/23 represents a multidrug-resistant Ng strain belonging to ST9363/NG-STAR 3194 and carrying mutations conferring resistance to fluoroquinolones, azithromycin, penicillin and tetracycline. Its phylogenetic placement within a European lineage highlights the global dissemination of HL-AziR and fluoroquinolone-resistant strains.
Carbapenem-resistant Enterobacteriaceae (CRE) pose a major public health threat due to extensive drug resistance and nosocomial spread. This study characterized the genome sequence of a multidrug-resistant E. coli strain EC6030 carrying blaNDM-5 recovered from a 10-month-old patient, and investigated its relationship to global blaNDM-5-positive E. coli. Whole-genome sequencing was performed to analyze antimicrobial resistance genes, virulence determinants, plasmid content, and the genetic context of blaNDM-5 in EC6030. A total of 7,606 blaNDM-5-carrying E. coli genomes were retrieved from the NCBI RefSeq database. Core-genome multilocus sequence typing, minimum-spanning tree analysis, and SNP-based phylogenetic analysis were used to assess global distribution and genetic relatedness. EC6030 was resistant to multiple antimicrobial classes, including β-lactams, carbapenems, fluoroquinolones, trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline, but remained susceptible to amikacin and gentamicin. Genomic analysis assigned EC6030 to ST410 and phylogroup C. The blaNDM-5 gene was located on a 46,161 bp IncX3 plasmid flanked by multiple insertion sequences. This plasmid showed high sequence similarity to previously reported blaNDM-carrying plasmids among E. coli and K. pneumoniae isolates in the public database. Globally, blaNDM-5-carrying E. coli strains are most prevalent in Asia, primarily from clinical specimens, and occur sporadically. The closest relative to EC6030 is a ST410 strain P24_WM1_05.20, recovered from the United Kingdom in 2020 which differing by 61 SNPs. These findings highlight the clinical significance and potential clonal and plasmid-mediated dissemination of blaNDM-5-carrying E. coli ST410 lineage and support strengthened genomic surveillance, antimicrobial stewardship, and infection control strategies globally.
The occurrence of colistin-resistant Escherichia coli in food-producing animals presents a global public health hazard. We aimed to determine the prevalence and molecular characteristics of mobilized colistin resistance (mcr)-carrying E. coli isolated from colistin-use and non-use pig farms. Antimicrobial susceptibility of isolated 552 E. coli from pig feces (n = 334) and their farm environments (n = 218) was assessed using broth microdilution. Molecular characterization of colistin-resistant E. coli was determined by polymerase chain reaction, multi-locus sequence typing, and next-generation sequencing (NGS). Colistin-resistant E. coli was detected in 4.7% (26/552) of isolates, from pigs (6.3%) and farm environments (2.3%), with significantly higher levels in colistin-use farms (P < 0.05). Among them, all carried mcr-1, except one isolate carrying mcr-3. We found 61.5% of isolates transferred the mcr-1 to E. coli J53 by conjugation. Replicon type IncI2 (57.7%) was predominantly detected in mcr-1-carrying plasmids. Common clones were ST101, ST10, and ST88, with identical STs found in different farms, suggesting clonal transmission. NGS analysis revealed the co-presence of mcr-1, blaCTX-M-55, and qnrS1 genes on megaplasmids. The plasmids also contain aminoglycosides, beta-lactams, sulfonamides, phenicols, and tetracycline resistance genes. Transposable elements IS26, ISEcp1, and orf477 were identified in the genetic environment of the blaCTX-M-55. The significant incidence of mcr-1 in pig farms may be due to the use of colistin, clonal spread, and horizontal spread of resistance genes. Thus, prudent antimicrobial use and biosecurity measures are necessary to prevent antimicrobial resistance in pig farms.
Rising clarithromycin (CLA) resistance complicates Mycobacterium abscessus (MAB) treatment. We evaluated berberine (BER) as a CLA adjuvant and explored factors potentially associated with its effect. Thirty MAB strains (29 clinical isolates with varying CLA susceptibility and ATCC 19977) were analyzed. Synergistic interactions were quantified via checkerboard and expressed as the fractional inhibitory concentration index (FICI), with time-kill kinetics for bactericidal activity. Gene expression (RT-qPCR), efflux pump activity (ethidium bromide accumulation), and biofilm inhibition were assessed. BER-CLA showed additive-to-synergistic effects (FICI ≤1) in all strains, reducing CLA MIC by ≥4-fold in 60.0% of isolates and achieving the susceptible breakpoint (≤2 µg/mL) in 61.1% of non-susceptible strains. A trend toward genotype-associated synergy appeared: all wild-type rrl or non-2269-2271 mutants showed synergy/partial synergy, versus only 50.0% of 2269-2271 mutants. BER transiently suppressed CLA-induced resistance genes (whiB7, erm(41), hflX) in non-A2270G mutants at early time points (1-3 h), but this effect waned at 24-48 h. It also downregulated efflux pump genes (MAB_2355c, MAB_1409c) and partially inhibited efflux activity. These findings suggest that BER potentiates CLA in association with suppression of inducible resistance and efflux, rather than acting via constitutive ribosomal mutations. Additionally, BER-CLA modestly reduced biofilm formation (P < 0.05), suggesting complementary benefit. BER appears to be a promising adjuvant for CLA treatment of MAB, with a trend toward enhanced activity in wild-type rrl strains and those without 2269-2271 mutations. These findings support developing BER-based strategies against CLA resistance, potentially in association with modulating inducible resistance.
To systematically delineate clinical, resistance and virulence profiles of Klebsiella variicola (Kv) and Klebsiella pneumoniae (Kp) to inform species-specific management strategies. A retrospective 1:4 matched case-control study enrolled 32 Kv and 128 Kp isolates from Xuanwu Hospital (Jan 2022-Dec 2025). Identification of isolates utilised MALDI-TOF MS and rpoB sequencing. Clinical characteristics, antimicrobial susceptibility, biofilm-forming capacity, serum resistance and genetic determinants were analysed using standard statistical methods. Among 2454 K. pneumoniae complex isolates, Kv accounted for 1.3%. Kv exhibited significantly lower resistance, particularly to carbapenems (3.1% vs. 35.2%; FDR-adjusted q < 0.001), lacking blaKPC entirely (0% vs. 30.5%). Both species were 100% susceptible to aztreonam-avibactam (AZA); however, one Kv harboured a transferable blaNDM. Kp showed higher carriage of classical virulence determinants (e.g., iutA+iucA, 28.1% vs. 0%) and greater serum resistance. Conversely, 90.6% of Kv lacked these genes, with 62.5% displaying high serum sensitivity. Although intra-abdominal Kv initially formed stronger biofilms (75.0% vs. 12.5%), multivariable regression revealed indwelling tubes (aOR: 6.84, P < 0.001), not species, independently drove robust biofilm formation. Clinical mortality did not differ significantly. Kp tends to exhibit stronger virulence and resistance profiles, whereas Kv appears to act primarily as an opportunistic pathogen linked to device vulnerabilities. Accurate differentiation may facilitate tailored management (e.g., source control), with AZA emerging as a promising therapeutic option. However, these single-centre findings warrant extensive validation in larger multi-centre cohorts.
This study investigated the molecular epidemiology, cross-resistance to novel antibiotics, and clonal distribution of carbapenem-resistant Pseudomonas aeruginosa (CRPA) clinical isolates. Forty-three CRPA isolates were collected from sterile clinical specimens in the Republic of Korea between 2015 and 2025. Susceptibility to 14 antibiotics was assessed in vitro by broth microdilution. Carbapenem-resistance mechanisms were characterized by using polymerase chain reaction, real-time quantitative reverse transcription polymerase chain reaction, and sequencing. Clonal diversity and epidemiological trends were examined by multilocus sequence typing. Among the 43 CRPA isolates, the susceptibility rates were 88.4% for both aztreonam-avibactam and cefiderocol, compared with 46.5% for ceftolozane-tazobactam and 39.5% for ceftazidime-avibactam. Among the 22 difficult-to-treat resistance P. aeruginosa isolates, susceptibility rates were 77.3% for aztreonam-avibactam and 86.4% for cefiderocol. Carbapenemase genes were detected in 46.5% of isolates, predominantly blaNDM (41.9%). Porin loss and efflux pump overexpression were observed in 83.7% and 23.3% of isolates, respectively. Among the 22 P. aeruginosa isolates non-susceptible to both ceftolozane-tazobactam and ceftazidime-avibactam, 90.9% and 77.3% remained susceptible to aztreonam-avibactam and cefiderocol, respectively. Multilocus sequence typing identified 12 sequence types (STs), with predominance of ST773 and ST644, both carrying blaNDM. CRPA exhibited multifactorial resistance driven by oprD disruption and blaNDM carriage within a diverse clonal structure dominated by ST773 and ST644. Aztreonam-avibactam and cefiderocol showed promising activity, supporting their role as critical therapeutic options.
Cancer patients often face etiological diagnosis challenges due to repeated hospitalizations, antibiotic exposure, and conventional microbiology tests (CMTs) limitations (low positivity, long turnaround). Metagenomic next-generation sequencing (mNGS) enables rapid and accurate pathogen detection, however, its clinical utility in cancer patients requires further investigation. Two years of mNGS results and clinical data of cancer patients in Sichuan Cancer Hospital were collected. The pathogens and antimicrobial resistance genes (ARGs) were analyzed. The diagnostic performance was evaluated via sensitivity, specificity, accuracy, positive and negative predictive value. The clinical significance in guiding antimicrobial therapy was assessed by comparing outcomes between mNGS-guided and empirical therapy groups. Multivariable logistic regression analysis was performed to explore risk factors for multidrug-resistant organisms (MDROs) and opportunistic pathogens infections in cancer population. The study included 340 mNGS results from 267 cancer patients. Streptococcus pneumoniae, Pseudomonas aeruginosa, Candida albicans and Epstein-Barr virus were the most common Gram-positive and Gram-negative bacteria, fungus and virus, respectively. The main ARGs were ESBLs and aminoglycoside resistance genes. mNGS showed high pathogen diagnostic sensitivity (97.50%) and moderate ARGs diagnostic sensitivity (64.29%). The mNGS-guided group had lower mortality (29.5% vs. 34.1%, p=0.65) and shorter duration of mechanical ventilation (39.34 ± 81.15 vs. 42.30 ±102.39 hours, p= 0.88). Age (p=0.028) and prior 90-day antibiotic use (p=0.047) independently predicted MDROs infections; immunodeficiency predicted Pneumocystis jirovecii (p=0.005) and Aspergillus spp. (p=0.010) infections. mNGS was reliable for pathogen diagnosis in cancer patients. However, its clinical significance on guiding antimicrobial therapy requires more prospective multicenter studies to confirm.
Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is an emerging multidrug-resistant pathogen with zoonotic potential. This study investigated the antimicrobial resistance, genomic diversity, and virulence characteristics of MRSP isolates from companion animals in South Korea. We analyzed 68 MRSP isolates collected from dogs and cats with skin or ear infections in Seoul between 2021 and 2023 using antimicrobial susceptibility testing and whole-genome sequencing. Antimicrobial resistance genes, staphylococcal cassette chromosome mec (SCCmec) types, multilocus sequence types (STs), virulence factors, and phylogenetic relationships were determined. All isolates were resistant to penicillin and oxacillin. High resistance rates were observed for cefovecin (98.5%) and tetracycline (89.7%). Sixty-seven isolates (98.5%) were resistant to at least three antimicrobial categories, with two resistant to ten classes. Multilocus sequence typing revealed 42 STs, including 11 novel STs; ST2842 (8.8%) and ST361 (7.4%) were most frequent. The mecA gene was universally present, and blaZ was detected in 97.1% of isolates. SCCmec typing identified type V (5C2&5) as predominant. Virulence profiling identified 60 of 67 investigated genes (89.6%) in at least one genome, with 39 genes (58.2%) conserved across all isolates. Phylogenomic analysis showed high genomic diversity but also close relatedness to human isolates. This study provides the first comprehensive genomic characterization of MRSP from companion animals in South Korea. The detection of strains closely related to human isolates underscores the likelihood of interspecies transmission. These findings highlight MRSP as a critical public health threat and the urgent need for surveillance and coordinated control strategies to limit its spread.
This study aimed to provide a narrative review of the history, characteristics, and progress of the ASIan Antimicrobial Resistance Surveillance Network (ASIARS-Net) system, an international web-based database system for antimicrobial resistance (AMR) surveillance. ASIARS-Net was compared with other surveillance platforms, particularly WHONET, a globally used AMR surveillance software supported by the World Health Organization, in terms of usability, AMR data analysis and outputs, and data management and integration, to clarify their complementary roles. The comparison was conducted based on experiences in countries that have implemented ASIARS-Net, enabling each participating country or hospital group to maintain a confidential database, process surveillance datasets from WHONET or Excel files, and generate national summaries and facility-level feedback reports. In Thailand, WHONET data from 74 hospitals (840,000 specimens), along with Excel data from three additional hospitals, each processing over 20,000 isolates annually, were processed to produce tailored feedback reports and enable comparisons across hospitals. In Vietnam, the use of ASIARS-Net together with WHONET or Excel is independently coordinated by laboratories. In 2024, eight hospitals successfully uploaded data and generated feedback reports, covering more than 140,000 bacterial isolates. Moreover, a nationwide clinical laboratory reported more than 90,000 isolates collected during 2022-2024. These reports not only showed clear trends but also highlighted higher isolation and resistance rates of specific inpatient AMR pathogens in Vietnam than in Japan. The ASIARS-Net system is evolving into a globally relevant platform complementary to WHONET for AMR surveillance and research at various scales.
This multicentre study aimed to evaluate the influence of continuous renal replacement therapy (CRRT) on the pharmacokinetics of colistin sulfate (CS) in critically ill patients and to propose optimized dosing regimens. Serial blood samples were obtained from critically ill patients receiving CS. Total CS concentrations were measured using a validated LC-MS/MS assay. The NONMEM software was utilized to develop the population pharmacokinetic (PopPK) model of CS and identify covariates influencing its pharmacokinetics. Monte Carlo simulations were conducted to optimize dosing regimens based on the probability of target attainment. Clinical efficacy, microbiological eradication, and adverse events of colisitn sulfate were also assessed. Logistic regression was conducted to identify clinical success predictors. A total of 123 critically ill patients with 370 plasma concentration measurements were included. 29 patients (23.6%) received CRRT during CS treatment. The final PopPK model was best characterized by a two-compartment structure, with creatinine clearance and CRRT significantly affecting CS clearance. Monte Carlo simulations indicated that patients undergoing CRRT required higher doses, and the use of a loading dose facilitated rapid target attainment. Overall, 68.3% of patients achieved clinical success, and bacterial eradication was 65.0%. Clinical efficacy was positively associated with longer treatment duration and negatively associated with vasoactive agent use. Notably, acute kidney injury occurred in 21.9% of patients during CS therapy. This study highlights the impact of CRRT on the pharmacokinetics of CS in critically ill patients, necessitating higher doses, and the use of a loading dose is recommended for rapid target attainment.