Purpose: To determine the occurrence of Listeria spp. and L. monocytogenesin distinct steps of bovine carcasses processing, and characterize the obtained isolates by phenotypic and genotypic methods.
Methods: Two hundred and nine (n = 209) bovine carcasses from three selected slaughterhouses from Minas Gerais state, Brazil, were surface sampled (400 cm²) in the following processing steps: A) after bleeding; B) after skinning; C) after evisceration, and D) after end washing. All samples were subjected to Listeria spp. detection following ISO 11.290-2, and suspect isolates were subjected to biochemical and serological identification by phenotypic tests. L. monocytogenes isolates were subjected to PCR reactions to identify their serological groups and virulence genes (inlA, inlB, inlC, inlJ, plcA, hlyA, actA and iap).
Results: Considering the bovine carcass processing steps, the following frequencies of positive results for Listeria spp. were recorded: A) 3/209; B) 1/209; C) 4/209, and D) 4/209; L. monocytogenes was recorded only in steps A (1/209) and D (1/209). Thirty isolates were identified as Listeria spp., being L. innocua (23), L. monocytogenes (5), and L. welshmeri (2). L. monocytogenes isolates presented positive results for all tested virulence genes; all isolates were serotyped as 1/2b by phenotypic test, while being identified by PCR as belonging to group “1/2c or 3c”.
Significance: The bovine carcass processing can be characterized as a potential source of L. monocytogenes contamination in slaughterhouses, despite the low frequency of occurrence of this foodborne pathogen. Acknowledgments: CNPq, CAPES, FAPEMIG, and Fundação Oswaldo Cruz.