Molecular typing and antimicrobial susceptibility profiles of Campylobacter jejuni and Campylobacter coli Isolates from Patients and raw meat in Huzhou, China, 2021-2022.

Background: Campylobacter species are zoonotic pathogens, and are considered to be the major foodborne pathogen that causes outbreaks and sporadic gastrointestinal illnesses both in developed and developing countries. In this study, the molecular typing and antimicrobial susceptibility profiles of Campylobacter jejuni and Campylobacter coli isolates from patients and raw meat between 2021 and 2022 in Huzhou were analyzed by using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and antimicrobial susceptibility testing.

Methods: From September 1, 2021 to December 31, 2022, a total of 342 fecal specimens from diarrheal patients at a sentinel hospital in Huzhou and 168 samples of raw meat products collected from farmers' markets and supermarkets, were subjected to Campylobacter isolation and identification. The agar dilution method was used to determine resistance of the Campylobacter isolates to eleven antibiotics. In addition, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed to compare their genetic relationships.

Results: 78 Campylobacter isolates were recovered, comprising 58 isolates (74.36%, 58/78) of Campylobacter jejuni (34 patient isolates and 16 food isolates) and 20 isolates (25.64%, 20/78) of Campylobacter coli (6 patient isolates and 14 food isolates). Campylobacter has emerged as a predominant foodborne pathogen in the local region, with detection rate reached 11.70% among 342 diarrhea samples. The Campylobacter isolation rate in 168 raw meat was 22.62% (38/168), all originating from poultry meat, with chicken been the major source of infection (86.84%, 33/38). Both PGFE type and MLST data confirmed that Campylobacter stains circulating in Huzhou are genetically diverse, with Campylobacter jejuni isolates being more diverse than Campylobacter Coli. PFGE typing revealed 45 band patterns among 54 Campylobacter jejuni strains and 17 band patterns among 19 Campylobacter Coli strains. 50 Campylobacter jejuni strains from different sources were classified into 37 ST types, showing a dispersed distribution and encompassing over 12 clonal complexes (CCs), with CC-21 being the most prevalent CC (22.00%, 11/50). The distribution of ST types in the 18 Campylobacter Coli strains was relatively concentrated, with 83.33% (15/18) of isolates belonging to the CC-828. In this study, 2 groups of Campylobacter jejuni strains (PFGE J2-ST464 and PFGE J9-ST-2328) originated from humans and chickens showed high genetic homologies by comparing PFGE and MLST results. Besides, some disagreement between PFGE and MLST was observed for certain ST, indicating a weak correlation between PFGE and MLST for certain Campylobacter strains. Most of the Campylobacter isolates were highly resistant to nalidixic-acid, ciprofloxacin and tetracycline. The multiple antibiotic resistance of Campylobacter Coli (89.47%) is higher than Campylobacter jejuni (29.63%).

Conclusion: Campylobacter is an important foodborne pathogen in both diarrheal patients and raw meat products in Huzhou City, exhibiting multiple antibiotic resistance and high level of genetic diversity.