Rastreamento de Listeria monocytogenes em industrias processadoras de queijo frescal tipo latino, nos Estados Unidos da America, empregando a subtipagem molecular . / Tracking of would listeria monocytogenes in processing industries of frescal cheese Latin type, in the United States of America, using the molecular subtipagem.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Latin-style fresh cheeses, which have been linked to at least two human listeriosis outbreaks in the US, are considered to be high risk foods for Listeria monocytogenes contamination. We evaluated L. monocytogenes contamination patterns in three Latin-style fresh cheese processing plants to gain a better understanding of L. monocytogenes contamination sources in the manufacture of these cheeses. Over a 6-month period, 246 environmental samples were collected and analyzed for L. monocytogenes using both the Food and Drug Administration (FDA) method and the Biosynth L. monocytogenes detection system (LMDS). Finished cheese samples from the same plants (n=111) were also analyzed by the FDA method, which was modified to include L. monocytogenes plating medium (LMPM) and the L. monocytogenes confirmatory plating medium (LMCM) used in the LMDS method. L. monocytogenes was detected in 6.3% of cheese and 11.0% of environmental samples. Crates, drains and floor samples showed the highest contamination rates with 55.6%, 30.0% and 20.6% L. monocytogenes positive samples, respectively. Finished products and food contact surfaces were positive in only one plant. The FDA method showed a higher sensitivity than the LMDS method for detection of L. monocytogenes from environmental samples. The addition of LMPM and LMCM media did not further enhance the performance of the FDA method for L. monocytogenes detection from finished products. Molecular subtyping (PCR-based allelic analysis of the virulence genes actA and hly and automated ribotyping) was used to track contamination patterns. Ribotype DUP-1044A, which had previously been linked to a 1998 multistate human listeriosis outbreak in the US, was the most commonly identified subtype (20/36 isolates) and was isolated from two plants. This ribotype was persistent and widespread in one factory, where it was also responsible for the contamination of finished products. We hypothesize that this ribotype may represent a clonal group with a specific ability to persist in food processing environments. While previous listeriosis outbreaks were linked to Latin-style fresh cheeses made from unpasteurized milk, the presence of this organism in pasteurized cheese products illustrates that persistent environmental contamination also represents an important source of finished product contamination.

ASSUNTO(S)

reação em cadeia de polimerase virulence (microbiology) molecular microbiology cheese microbiologia molecular listeria monocytogenes queijo listeria monocytogenes virulencia (microbiologia)

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