Occurrence and molecular characteristics of Listeria monocytogenes isolated from ready-to-eat meats in Hanoi, Vietnam

Listeria monocytogenes represents one of the most serious threats to food safety. Several studies have shown that Ready-To- Eat (RTE) meats are an important vehicle responsible for listeriosis in human. In Vietnam, little is known about the occurrence and molecular characteristics of L. monocytogenes in meat products, which are essential for developing monitoring plans and control measures. In the present study, we investigated the occurrence of L. monocytogenes in 258 sausage and sliced meat samples collected during the period of 2013-2015 and determined the genetic diversity of the isolates using multi-locus sequence typing (MLST). Overall, L. monocytogenes was present in 19/129 (14.7 %) and 40/129 (31.0 %) sausage and sliced meat samples respectively, with the peak of occurrence being in summer. Furthermore, a minimum spanning tree was constructed based on MLST data of 47 isolates. A total of 15 sequence types were found, with five being novel. Notably, the majority of the isolates (34/47) belonged to the hypervirulent clonal complexes 1, 2, and 3.