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BioMed Research International
Volume 2014 (2014), Article ID 742032, 12 pages
Research Article

Phenotypic and Genotypic Characterization of Atypical Listeria monocytogenes and Listeria innocua Isolated from Swine Slaughterhouses and Meat Markets

1Laboratório Prática de Saúde Pública, Faculdade de Saúde Pública, Universidade de São Paulo, Avenida Doutor Arnaldo , No. 715, 01246 904 São Paulo, SP, Brazil
2Laboratório de Sanidade Suína e Virologia, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, Avenida Professor Doutor Orlando Marques de Paiva, No. 87, Cidade Universitária, 05508 270 São Paulo, SP, Brazil
3Laboratório de Zoonoses Bacterianas, Fundação Instituto Oswaldo Cruz, Avenida Brasil 4365, Manguinhos, 21040 360 Rio de Janeiro, RJ, Brazil

Received 23 February 2014; Accepted 3 May 2014; Published 28 May 2014

Academic Editor: Stanley Brul

Copyright © 2014 Luisa Zanolli Moreno et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In the last decade, atypical Listeria monocytogenes and L. innocua strains have been detected in food and the environment. Because of mutations in the major virulence genes, these strains have different virulence intensities in eukaryotic cells. In this study, we performed phenotypic and genotypic characterization of atypical L. monocytogenes and L. innocua isolates obtained from swine slaughterhouses and meat markets. Forty strains were studied, including isolates of L. monocytogenes and L. innocua with low-hemolytic activity. The isolates were characterized using conventional phenotypic Listeria identification tests and by the detection and analysis of L. monocytogenes-specific genes. Analysis of 16S rRNA was used for the molecular identification of the Listeria species. The L. monocytogenes isolates were positive for all of the virulence genes studied. The atypical L. innocua strains were positive for hly, plcA, and inlC. Mutations in the InlC, InlB, InlA, PI-PLC, PC-PLC, and PrfA proteins were detected in the atypical isolates. Further in vitro and transcriptomic studies are being developed to confirm the role of these mutations in Listeria virulence.