Prevalence, abundance, serovars and antimicrobial resistance of Salmonella isolated from retail raw poultry meat in China

Abstract

This study investigated the prevalence and levels of Salmonella contamination of retail raw poultry meat in China, and examined serovar distribution and antimicrobial susceptibility profiles of the recovered isolates. In total, 664 poultry meat samples were collected from retail markets in 39 cities across China. Salmonella was isolated from 249 (37.5%) samples, including 190 (36.7%) chicken, 48 (40.7%) duck and 11 (39.2%) pigeon samples. The most probable number (MPN) values of 36.1% of the positive samples ranged from 0.3 to 10 MPN/g, with three samples exceeding 110 MPN/g. Among the 667 Salmonella isolates, 35 serovars and 42 multilocus sequence typing patterns were identified. Predominant serovars included Salmonella enterica serovar Enteritidis (32.7%), Salmonella enterica serovar Indiana (14.2%) and Salmonella enterica serovar Typhimurium (11.9%), while two novel STs were identified (ST7352 and ST7612). Except for one unnamed strain (4,12:d:-), all of the identified serovars have previously been linked to human infections. Antimicrobial susceptibility testing of the 318 non-duplicate isolates revealed that only 5 (1.6%) were susceptible to all 22 tested antimicrobials, while 191 (60.1%) exhibited resistance to at least three classes of antimicrobials. The highest levels of resistance were observed for nalidixic acid (72.3%), followed by ampicillin (55.3%) and streptomycin (48.7%). Of particular concern was the detection of highly multidrug-resistant Salmonella enterica serovar Indiana isolates, most (84.1%) of which showed co-resistance to ciprofloxacin and ceftriaxone. Overall, our findings showed a high prevalence of Salmonella contamination of retail raw poultry meat, which could expose consumers to multidrug-resistant isolates. This study provides comprehensive data for evaluation of new control measures for Salmonella contamination of poultry.

Keywords: Antimicrobial resistance; MPN; Poultry meat; Prevalence; Salmonella; Serovar.