Retail wet markets, food handlers, and hospitalised patients as nodes in a shared non-typhoidal Salmonella ecosystem: a one health molecular epidemiological pilot study in Wuhan, China.

BACKGROUND

Non-typhoidal Salmonella (NTS) is a leading foodborne pathogen in China, yet the transmission dynamics linking retail wet markets, food handlers, and hospitalised patients remain poorly characterised. Using a One Health framework, we investigated whether genotypically related Salmonella populations circulate across these three source categories in Wuhan.

METHODS

Thirty-two non-duplicate Salmonella isolates were recovered from retail meat at four wet markets (n = 9), anal swabs of food handlers (n = 7), and stool cultures of paediatric inpatients (n = 16) in Wuhan (June 2022-September 2023). All isolates underwent serotyping, antimicrobial susceptibility testing (17 agents), resistance gene PCR, biofilm assay, and XbaI-PFGE genotyping.

RESULTS

Nineteen isolates (59.4%) were multidrug-resistant (MDR). blaCTX-M was the predominant β-lactamase gene (17/32, 53.1%) and was absent from all food-handler isolates (0/7), which instead displayed a distinctive tetracycline-trimethoprim-sulfamethoxazole-chloramphenicol (TCY/SXT/CHL) co-resistance profile with elevated sul3 prevalence (3/7, 42.9%). PFGE resolved four clusters (A-D); two cross-source clusters (A and D) suggested genetic relatedness warranting whole-genome sequencing (WGS) confirmation. Cluster D provides the first molecular signal of a possible link between an asymptomatic food-handler S. Enteritidis carrier and hospitalised patients (B34-XL112, 95.7% PFGE similarity). A single clinical isolate (XL48, Cluster D) exhibited strong biofilm formation.

CONCLUSIONS

Food handlers may represent an underexamined node connecting retail food environments and hospitals in this NTS ecosystem. These findings support integrating food-handler surveillance into food safety and hospital infection control programmes, with WGS recommended to confirm or refute the candidate clusters identified by PFGE.