An outbreak of foodborne disease caused by Salmonella Isangi in Yuyao, Zhejiang, 2018

ObjectiveTo investigate an outbreak of foodborne disease caused by Salmonella Isangi in Yuyao, Zhejiang province, in 2018, and analyze the biological and epidemiological characteristics, molecular typing and drug sensitivity characteristics of isolated pathogens.

MethodsPathogenic bacteria were detected according to national standard in suspicious food samples. Salmonella was identified by systematic biochemical and serum typing methods. Drug sensitivity test was carried out with disk diffusion method. Pulse-field gel electrophoresis (PFGE) and whole genome sequencing (WGS) were used for molecular typing analysis. The patients' medical record analysis and follow-up were conducted in the epidemiological investigation.

ResultsThree strains of Salmonella Isangi were isolated from 1 food sample (roast duck) and 2 patient stool samples. The isolates were resistant only to cotrimoxazole. PFGE band pattern was completely consistent. Multilocus sequence typing (MLST) showed that the strains belonged to ST216. wgMLST analysis showed that there was an allelic difference between two isolates from the patients. Furthermore, all of them carried 126 known virulence genes and a aminoglycoside antibiotic resistance gene aac(6)-Iaa.

ConclusionIt is confirmed that the outbreak of foodborne disease was caused by the consumption of roast duck contaminated by Salmonella Isangi ST216, which was first reported in Yuyao.