Quantitative surveys of Salmonella and Campylobacter on retail raw chicken in Yangzhou, China

Abstract

To assess the risks to consumers from Salmonella and Campylobacter in whole raw chickens sold in Yangzhou City, 12-month quantitative surveys were performed in succession. In this study, 480 samples were collected from supermarkets and wet markets from 2011 to 2013. The examination method of Salmonella was optimized from the most probable number (MPN), and the level of Campylobacter contamination was tested using the direct plating method. These results showed that the positive rates of Salmonella and Campylobacter were 33.8% and 51.3%, respectively, and the corresponding mean values of enumeration were 0.524 MPN/g and 1473.49 colony-forming units/g. For prevalence and loads of Salmonella, there was no significant difference between supermarkets and wet markets. However, for Campylobacter, the contamination level of wet markets was greater compared to supermarkets. Seasonality was observed in both qualitative and quantitative studies for both pathogens, with summer being the high-incidence season. Diversity among Salmonella isolates was high in terms of serovar, and the dominant serotypes were Salmonella Typhimurium (34.6%) and Salmonella Enteritidis (16.7%). Diversity of Campylobacter isolates demonstrated that Campylobacter jejuni (45.5%) and Campylobacter coli (30.9%) were the most common species, except for the mixed contamination. Survey results indicated that there was a need for more interventions to minimize the exposure of consumers to Salmonella and Campylobacter.