Highly prevalent multidrug resistance and QRDR mutations in Salmonella isolated from chicken, pork and duck meat in Southern China, 2018–2019

This study was undertaken to investigate the prevalence, serotype distribution and antimicrobial resistance in Salmonella isolated from retail meat in Southern China, and to characterize the major mechanisms that mediate the ciprofloxacin resistance of isolates. High levels of Salmonella contamination were detected in pork (67.0%), duck (50.5%) and chicken (46.2%). Thirty different serotypes were identified among 500 detected Salmonella isolates, as well as significant differences in serotypes between different retail meat samples. Notably, 405 (80.1%) isolates exhibited multidrug resistance (MDR). Meanwhile, we also found that 74 (14.8%) Salmonella isolates were resistant to ciprofloxacin and the major mechanisms underlying this resistance were investigated. The commonest mutations in gyrA S83F (40.5%) and D87N (35.1%), and in parC was T57S (71.6%) and S80I (35.1%). Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) analysis revealed that the S. Kentucky isolates that were resistant to ciprofloxacin mostly belonged to ST198 (21/23, 91.3%) and PFGE revealed the presence of various genotypes. This study identified a diversity of Salmonella serotypes and a high prevalence of multidrug resistance (MDR) among Salmonella isolated from retail meat in Southern China, which indicates that foodborne Salmonella potentially constitutes a potential food safety risk.