[Quantitative detection on contamination of Listeria monocytogenes isolated from retail ready-to-eat meats in Beijing].

Objective: To survey the contamination of L. monocytogenes isolated from retail ready-to-eat meats in Beijing.

Methods: Ready-to-eat meats were quantitatively detected for L. monocytogenes using MPN method. L. monocytogenes isolates were analyzed by PFGE.

Results: Fourteen out of 197 ready-to-eat meat samples were positive for L. monocytogenes with the contamination rate of 7.11% and the geometry mean contamination level of 14.31 MPN/g. The contamination of L. monocytogenes isolated from free trade market (13.89%) was more severe than those from specificity store (8.57%), supermarket (5.75%) and restaurant (2.56%), while supermarket had the highest mean contamination level of 22.78 MPN/g. A total of 13 PFGE types were characterized using DICE-UPGMA analysis through BioNumerics 7.1 software. There were two isolates from the same free trade market share the same PFGE type, which suggested the same contamination source of both samples.

Conclusion: Contamination of L. monocytogenes exist in retail ready-to-eat meats. The contamination level of L. monocytogenes isolated from free trade market is more severe than those from specificity store, supermarket and restaurant.