Enumeration and characterization of Salmonella isolates from retail chicken carcasses in Beijing, China.

Epidemiological reports have implicated contaminated raw or undercooked chicken as primary vehicles of Salmonella transmission to human beings. Risk assessments relating to Salmonella contamination of poultry products in China are frequently hampered by the lack of quantitative data. In this study, whole chicken carcasses (n=395) were collected from the retail markets of Beijing, and the level of Salmonella contamination was enumerated by most probable number (MPN) analysis and all Salmonella isolates were further characterized for their serotypes and antimicrobial resistance. Overall, 49.9% (197/395) of the retail whole chicken carcasses were contaminated by Salmonella and the MPN values ranged from 1.5 to >550 MPN/100 g. The 50% percentile of Salmonella MPN value was 7.5 MPN/100 g in chicken carcass. The predominant serotypes isolated were Salmonella Enteritidis (n=309, 94 samples), Salmonella Indiana (n=205, 54 samples) and Salmonella Infantis (n=89, 23 samples). Multidrug-resistant Salmonella isolates were recovered from 100 chicken carcass samples; 102 isolates (from 41 chicken carcasses) even showed resistance to both ciprofloxacin and cefotaxime. Our findings showed a high prevalence of Salmonella contamination in retail chicken carcasses, which could be a source of exposure for consumers to multidrug-resistant isolates. This study provided baseline enumeration data for the risk assessment and evaluation of new control measures of Salmonella contamination in retail chicken products.