Distribution of serotypes and genotypes of ESBL-producing Salmonella in the pork production chain in different regions of China

Salmonella is the most common foodborne pathogen worldwide, and livestock and poultry products are the main attributed foods to Salmonellosis, The widely spread of ESBL-producing Salmonella increases the difficulty of treatment of infection. In order to clarify the epidemic characteristics, serotype distribution and genotypic characteristics of ESBL-producing Salmonella in the pork production chain, ESBL-producing Salmonella was screened from strains isolated from the pork production chain in six regions of China (Central, South, East, Northeast, Southwest, and Northwest). The serotypes and multilocus sequence typing (MLST) were identified by PCR, and the genetic correlation of Salmonella in the pork production chain among different regions was analyzed by combining PFGE. The results showed that the overall detection rate of ESBL-producing Salmonella was 4.86%, with the highest positivity rates within each subgroup in the Northwest (8.82%), breeding (7.37%), and feces (18.93%). A total of 15 serotypes were identified for all Salmonella , with the dominant serotype being S . 1,4,[5],12:i:- (33.33%). S . Typhimurium and ST34 are dominant in the Southwest, Northwest and Central regions, as well as in the process of breeding and cutting, and also in the feces, lymph nodes and pork. S . Rissen and ST469 are dominant in the South, slaughtering and carcasses. S . Typhimurium and ST19 are dominant in the East region. Three serotypes of ESBL-producing Salmonella were identified, and the dominant serotype was also S . 1,4,[5],12:i:-. A total of 16 different sequence types (STs) were identified in all Salmonella , of which the predominant was ST34 (38.19%). Two STs were found in ESBL-producing Salmonella . ST34 (85.71%) was also dominant. 105 strains of S . 1,4,[5],12:i:- and S . Typhimurium identified 71 PFGE profiles, of which nine profiles were found in ESBL-producing Salmonella . There are strains with 100% homology between different regions, processes, and samples suggests a risk of cross-transmission. The results of this study may provide a reference for public health and food safety epidemiological investigations caused by ESBL-producing Salmonella . • The ESBLs positivity rate for Salmonella was 4.86%,with the highest in the Northwest. • 15 serotypes were identified for all strains, S . 1,4,[5],12:i:- were the dominant serotypes. • A total of 16 STs were identified in all strains, with ST34 being the dominant STs. • 72 PFGE bands were detected in 105 S. 1, 4, [5], 12:i:- and S. Typhimurium strains.