Isolation and characterization of Salmonella in pork samples collected from retail and wholesale markets in each season from 2016 to 2018 in Wuhan, China

Aims To investigate the prevalence and characteristics of Salmonella in pork on sale in Wuhan, Central China. Methods and Results A total of 4744 pork samples were collected from retail or wholesale markets in each season from 2016 to 2018. The samples showed an overall Salmonella prevalence of 19 center dot 54% (927/4744), among which the samples collected in 2017 (21 center dot 67%, 428/1975) possessed a significantly higher prevalence than those collected in 2016 (18 center dot 61%, 209/1123) (P = 0 center dot 047) or 2018 (17 center dot 51%, 290/1656) (P = 0 center dot 002), and the samples collected in winter showed the lowest prevalence (15 center dot 86%, 177/1116). The Salmonella prevalence was significantly higher among samples from retail markets (25 center dot 68%, 283/1102) than wholesale markets (17 center dot 68%, 644/3642) (P = 0 center dot 000). Antimicrobial resistance of 922 Salmonella strains was tested by determining the minimal inhibitory concentrations using a broth microdilution method. The strains revealed that 98 center dot 92% (912/922) were resistant to at least one of the antimicrobial agents, and 80 center dot 04% (738/922) were resistant to three or more antimicrobials (MDR). Resistance to sulfamethoxazole/trimethoprim (89 center dot 91%), tetracycline (87 center dot 20%) and ampicillin (71 center dot 69%) was predominant. The proportion of MDR strains in 2017 (93 center dot 62%, 396/423) was significantly higher than that in 2016 (63 center dot 16%, 132/209) (P = 0 center dot 000) or 2018 (69 center dot 66%, 202/290) (P = 0 center dot 000). No significant difference was observed in the proportions of MDR strains between wholesale markets (76 center dot 07%, 213/280) and retail markets (80 center dot 53%, 517/642) (P = 0 center dot 075). Multi-locus sequence typing for 554 of the isolates revealed 20 different sequence types (STs), among which ST40 (38 center dot 27%, 212/554), ST34 (18 center dot 41%, 102/554) and ST469 (14 center dot 46%, 79/554) were dominant. Conclusions A high risk of Salmonella prevalence and antimicrobial resistance was observed in pork in Wuhan. The risk varies between different sampling years, seasons and market types. Significance and Impact of the Study Providing baseline data on Salmonella contamination in pork on sale in Central China.