Molecular and epidemiologyical analysis of a Campylobacter jejuni outbreak in China, 2018.

Introduction: Campylobacter spp. is the most common gastrointestinal pathogen worldwide with a very low reported incidence in China. In April 2018, one 36 cases of diarrhea outbreak occurred in a high school in Beijing after a trip to another province in Southern China. The investigation for the enteric pathogen infection was conducted to identify the cause. Methodology: Eighteen stool specimens from 11 diarrheal patients and 3 close contacts were collected and tested for 16 enteric bacterial and viral pathogens using real-time PCR methods. Multilocus Sequence Typing (MLST), pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility testing were applied to C. jejuni isolates in this outbreak in order to characterize the incident. Results: Ten (90.9%) of 11 stool specimens from diarrheal patients were positive for Campylobacter jejuni, confirmed as the cause of outbreak. Eight C. jejuni strains were obtained and produced 2 sequence types (STs) and 3 PFGE patterns. Six of them had the same ST (ST2274) and PFGE pattern (SMA001). The dominant outbreak strain with an identical subtyping profile was clustered with most chicken isolates from national MLST and PulseNet Campylobacter database. The entire 8 isolates were multi-drug resistant, with the dominant resistance pattern of nalidixic acid, tetracycline and ciprofloxacin combined, except for 2 isolates resistant to florfenicol. Conclusion: Molecular typing confirmed that most of the cases belonged to a clonal cluster supporting the hypothesis of a common source; however, the source was not identified. This was the first recognized Campylobacteriosis outbreak in China among 20 years.