Listeria monocytogenes in green vegetables: isolation and serotyping

Abstract

Consumption of food contaminated with Listeria monocytogenes poses as a risk to human health. Ninety-seven samples of green leafy vegetables marketed in the state of Rio de Janeiro were analyzed for detecting L. monocytogenes by selective enrichment. Thirty-five in natura green vegetables, 32 minimally processed samples and 30 ready-to-eat raw salads samples were assessed. The isolates were serotyped by means of classical seroagglutination technique using somatic and flagellar polyclonal antisera. Seven samples (7.2 %) showed to be contaminated with L. monocytogenes, being two in natura samples and five ready-to-eat salads. All isolates were identified as serovar 1/2a. Considering these findings on the contamination of in natura green vegetables with L. monocytogenes, the consumers should be advised regarding to the possibility of this kind of product to be contaminated with this pathogen, and also to imply vigilance in observing the proper sanitization procedures to avoid the cross-contamination with other foods. Occurrence of L. monocytogenes in ready-to-eat salad samples denotes a health hazard to consumers, especially to those who belong to risk groups.