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

J Appl Microbiol. 2020 Mar;128(3):875-883. doi: 10.1111/jam.14515. Epub 2019 Nov 29.

Abstract

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

Keywords: Salmonella; antimicrobial resistance; multi-locus sequence typing; pork; prevalence.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Anti-Infective Agents / pharmacology
  • China
  • Drug Resistance, Bacterial / drug effects
  • Drug Resistance, Bacterial / genetics
  • Food Microbiology*
  • Microbial Sensitivity Tests
  • Multilocus Sequence Typing
  • Pork Meat / microbiology*
  • Prevalence
  • Salmonella / classification
  • Salmonella / drug effects
  • Salmonella / genetics
  • Salmonella / isolation & purification*
  • Seasons
  • Swine

Substances

  • Anti-Infective Agents