[Serotype distribution and antimicrobial resistance of Salmonella isolates from retail chicken carcasses in six provinces of China].

Objective: To obtain the serotype diversity and antimicrobial resistance of Salmonella isolates recovered from retail chicken carcasses for sale in six regions of China. Methods: From August 2010 to March 2012, each month 20 retail chicken carcasses including freshly slaughtered, chilled and frozen samples were collected from supermarkets and farmer's markets in 7 monitoring sites in Beijing, Jilin province, Inner Mongolia Autonomous, Shanxi province, Jiangsu province and Guangdong province, respectively. Samples were routinely collected for 12 months for each site. 1 680 chicken carcasses were collected in total and 2 629 Salmonella strains were isolated by PCR and biochemical method. Luminex xMAP method and classical slide agglutination method were carried out to determine isolates' serotypes. Minimal inhibitory concentrations (MICs) of 10 classes of antimicrobials including 14 agents were determined using broth micro-dilution method. Mocular methods were used to determine antimicrobial resistance genes of CIP-CTX-CT co-resistant isolates. Results: In all, 2 629 Salmonella isolates, there were 17 seorgroups and 58 serotypes, B and D1 were the dominant serogroups with rates of 34.7% (n=913) and 31.0% (n=815), Enteritidis (30.8%, n=810), Indiana (17.6%, n=463), Infantis (10.6%, n=278) were the top three serovars. We found 224 CIP-CTX co-resistant S. Indiana containing 3 colistin resistant strains, one of them carrying mcr-1 gene and being ESBLs positive, which demonstrated a nine multi drug resistance against 11 antimicrobials tested. Conclusion: These data began to describe the complicated serovar diversity and heavy antimicrobial resistance of Salmonella isolates recovered from retail chicken carcasses in six regions of China. The findings highlight the emergence of ciprofloxacin and cefotaxime co-resistant S. Indiana and also a mcr-1 positive S. Indiana with heavy multi drug resistance.