Prevalence and characterization of Listeria monocytogenes isolated from retail-level ready-to-eat foods in South China

Listeria monocytogenes is an important food-borne pathogen causing meningitis, meningoencephalitis and abortion. To assess the potential risk to consumer health, the presence of L monocytogenes was investigated using qualitative and quantitative methods. Ten (6.33%) of 158 retail RTE food samples were positive for L monocytogenes and the contamination levels were less than 10 MPN/g,while none of 65 dairy products was positive for L monocytogenes. The 37 strains were grouped into five clusters and two singletons, five clusters and two singletons, and three clusters and one singleton by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) and RAPD fingerprint respectively, at similarity coefficient of 80%. The susceptibility test showed that 83.8% were susceptible to 15 antimicrobials; two were penicillin-resistant, and one was multidrug-resistant to kanamycin, tetracycline, sulfamethoxazole, rifampin, gentamycin, penicillin, and ampicillin. Virulent L monocytogenes that possess partial antimicrobial resistance, and serotypes frequently associated with listeriosis were recovered from RTE foods. Consumers may, therefore, be exposed to potential risks of L inonocytogenes infection in South China. This study contributed to the prevalence and contamination levels of L monocytogenes in RTE foods in South China for the first time, providing baseline information for Chinese regulatory authorities to formulate a regulatory framework for controlling L monocytogenes to improve the microbiological safety of RTE foods. (C) 2013 Elsevier Ltd. All rights reserved.