Emergence and characterization of CC398 S. aureus isolates from Boiled Salted Goose in eastern China

Staphylococcus aureus is an important foodborne pathogen that causes human gastroenteritis worldwide through the secretion of staphylococcal enterotoxins in food. Consumption of contaminated raw food or cooked food handled by S. aureus carriers is the primary cause of staphylococcal food poisoning. In this study, a one-year surveillance of S. aureus in Boiled Salted Goose was conducted in Yangzhou, eastern China. Among 312 samples collected from eight street carts between August 2023 and September 2024, 24 S. aureus isolates were identified, with a prevalence rate of 7.7%. Cart E showed the highest prevalence (40.5%), and goose heart exhibited the highest contamination rate among tissues (18.4%). Whole-genome sequencing analysis revealed four clonal complexes (CC1, CC5, CC8, and CC398), including four CC398 isolates rarely reported in Ready-to-Eat (RTE) foods in China. Phylogenetic analysis divided the 24 isolates into two clades: Clade I contained four CC398 isolates carrying the GrlB(E422D) mutation, and Clade II included one ST630 isolate with the resistance profile msr (A) -tet (K) -blaZ-fusB . Two isolates displayed resistance to ciprofloxacin associated with double mutations GrlA(S80F) and GyrA(S84L). The widespread presence of γ-hemolysin, enterotoxin, and biofilm-associated genes suggests that S. aureus may persist in Boiled Salted Goose. These findings highlight the potential public health relevance of contaminated RTE foods and warrant further surveillance.