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Objectives: Campylobacter is a significant zoonotic pathogen primarily transmitted through poultry. Our study aimed to assess antimicrobial resistance and genetic relationships among Campylobacter isolates from retail chicken meat and humans in Taiwan. Methods: Campylobacter isolates were analysed using whole-genome sequencing to investigate their antimicrobial resistance, genetic determinants of resistance, and genotypes. Results: Campylobacter coli and Campylobacter jejuni accounted for 44.9% and 55.1% of chicken meat isolates, and 11.4% and 88.6% of human isolates, respectively. C. coli displayed significantly higher resistance levels. Furthermore, isolates from chicken meat exhibited higher levels of resistance to most tested antimicrobials compared to isolates from humans. Multidrug resistance was observed in 96.3% of C. coli and 43.3% of C. jejuni isolates from chicken meat and 80.6% of C. coli and 15.8% of C. jejuni isolates from humans. Macrolide resistance was observed in 85.5% of C. coli isolates, primarily attributed to the erm(B) rather than the A2075G mutation in 23S rRNA. Among the 511 genomes, we identified 133 conventional MLST sequence types, indicating significant diversity among Campylobacter strains. Notably, hierarchical Core-genome multilocus sequence typing clustering, including HC0, HC5, and HC10, revealed a significant proportion of closely related isolates from chicken meat and humans. Conclusions: Our research highlights significant associations in antimicrobial resistance and genetic relatedness between Campylobacter isolates from chicken meat and humans in Taiwan. The genetic analysis data suggest that campylobacteriosis outbreaks may occur more frequently in Taiwan than previously assumed. Our study emphasizes the need for strategies to control multidrug-resistant strains and enhance outbreak prevention.

ABSTRACT: Objectives: We investigated the temporal trends of Salmonella enterica serovar Typhimurium (S. Typhimurium) clones in Taiwan from 2004 to 2019, focusing on antimicrobial resistance (AMR), resistance genetic determinants, and plasmid types. Methods: Salmonella isolates were characterized using pulsed-field gel electrophoresis (PFGE), whole-genome sequencing, and antimicrobial susceptibility testing. Clones were defined using PFGE clustering and the hierarchical cgMLST clustering (HierCC) assignments. Results: Seven major S. Typhimurium clones, HC100_2, 13, 41, 305, 310, 501, and 46261, accounted for 97.6% (8079/8275) of human isolates in Taiwan. Each clone displayed a unique AMR profile, resistance genetic determinants, and plasmid types. Four highly resistant clones (HC100_2, 41, 305, and 310) exhibited multiple resistance in 86.5% to 96.1% of isolates. HC100_305 and HC100_2 were pandemic multidrug-resistant clones, characterized by resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT) and ASSuT, respectively. The prevalence of the ACSSuT clone decreased from 68.7% of S. Typhimurium isolates in 2004 to 1.7% in 2019, while the ASSuT clone emerged in 2007 and became the largest clone after 2010. Several plasmids, including IncHI2-IncHI2A, IncC, IncFIB(K), and IncI1–1(α), carried multiple resistance genes or were associated with the carriage of mph(A), blaCMY-2, and blaDHA-1. Conclusions: Between 2004 and 2019, Taiwan experienced the emergence, prevalence, and subsequent decline of several highly resistant S. Typhimurium clones. The clones defined using the HierCC approach have global comparability. The increasing resistance to third-generation cephalosporins, cephamycins, ciprofloxacin, and azithromycin in recent years poses a significant medical concern.

ABSTRACT: Objectives: A nosocomial salmonellosis outbreak caused by Salmonella enterica serovar Goldcoast occurred in a respiratory care ward (RCW) of a hospital in central Taiwan between December 24, 2020, and January 21, 2021. Ten isolates recovered from 10 RCW residents were resistant to extended-spectrum cephalosporins. The resistance mechanism needs to be investigated. Methods: Whole-genome sequencing and antimicrobial susceptibility testing were conducted to determine the genetic resistance determinants and the phenotypic resistance in the isolates. Results: Each of the 10 outbreak isolates harbored an IncHI2 plasmid that carried 15 antimicrobial resistance genes aac(3)-IId, aadA22, aph(3’)-Ia, aph(6)-Id, arr-2, blaCTX-M-55, blaLAP-2, blaTEM-1, dfrA14, floR, lnu(F), qnrS13, sul2, sul3, tet(A), an efflux pump regulatory gene ramAp and an IncL plasmid carried a blaOXA-48. The outbreak strains were expected to be resistant to numerous antimicrobials, including aminoglycosides, b-lactams /inhibitors, tetracycline, rifamycin, lincosamide, sulfonamides, trimethoprim, phenicols, fluoroquinolones, and carbapenems. Two outbreak isolates displayed higher minimum inhibitory concentrations than the other eight isolates to cefmetazole and carbapenems, which was linked to a deficiency of a major facilitator superfamily transporter in the two isolates. Conclusion: The carbapenem-resistant outbreak strains could have been derived from extensively drug-resistant S. enterica Goldcoast strains, which have been a major pathogen in Taiwan since 2018, through the acquisition of a blaOXA-48-carrying plasmid. Special efforts are needed in Taiwan to monitor the spread of extremely resistant strains.