Comparison of Antibiotic Resistance Profiles of Salmonella Isolates from Retail Meats in Nanchang, China, in Two Periods.

ABSTRACT

Salmonella is one of the most important foodborne pathogens. In this article, a total of 160 Salmonella isolates recovered from retail meats in June-July 2018 (before COVID-19 outbreak) and December 2020-April 2021 (after COVID-19 outbreak) in Nanchang, China, were characterized for serotyping, antimicrobial susceptibility, and specific resistance gene screening. The prevalence of Salmonella Typhimurium increased from 5.4% in 2018 to 19.1% in 2021, and Salmonella Enteritidis increased from 3.3% in 2018 to 8.8% in 2021. Compared with those in June-July 2018, Salmonella isolates in December 2020-April 2021 demonstrated a significant increase in resistance to 13 tested antibiotics except for doxycycline and nitrofurantoin (p < 0.05). The Salmonella isolates in December 2020-April 2021 showed a higher presence of plasmid-mediated quinolone resistance genes (qnrA, qnrB, and qnrS), and mutations in the quinolone resistance-determining region (gyrA Asp87Asn, gyrA Asp87Tyr, parC Thr57Ser, and parC Ser80Ile). Whole-genome sequencing was used to analyze four polymyxin B-resistant strains. Some common mutation sites in eptC and micA were found in the four strains. Based on the data in this article, it indicated that antibiotic resistance was facilitated and more gene mutations related to quinolone resistance were developed.