Prevalence and Virulence Characterization of Listeria monocytogenes in Chilled Pork in Zhejiang Province, China.

Listeria monocytogenes is an important foodborne pathogen that can grow in refrigeration temperature and causes severe human infections. The aims of this work were to estimate the prevalence of L. monocytogenes in chilled pork in Zhejiang, China and to examine the virulence features of the isolates. Of 331 meat samples, 196 were positive for Listeria spp., with L. innocua accounting for 54.4%, L. monocytogenes for 11.5%, and L. welshimeri for 4.2%. The most prevalent L. monocytogenes serotype was 1/2c (60.5%), followed by serotypes 1/2a (28.9%), 1/2b (7.9%), and 4b (2.6%). All L. monocytogenes isolates contained virulence-associated genes examined. Adhesion and invasion ability of serotype 1/2c isolates was much lower than those of other serotypes. Only one isolate was defective in cell-to-cell spread. These findings are important for risk assessment of chilled pork as a source of potential transmission of L. monocytogenes to other food products, particularly to ready-to-eat food products.