Caracterização fenotípica e molecular de isolados de Listeria monocytogenes obtidos em uma planta de processamento de carne bovina

• Autor(a) principal: Camargo, Anderson Carlos
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5150
• topic: Listeria; Carne bovina; PFGE; Listeria; Beef; PFGE; CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA::INSPECAO DE PRODUTOS DE ORIGEM ANIMAL

Listeria monocytogenes is a foodborne pathogen often associated to beef cuts and meat products. Its presence in beef cuts is usually related to cross contamination during processing, once L. monocytogenes is naturally part of its environmental microbiota. The consumption of food contaminated with this pathogen, mainly ready-to-eat products, can determine listeriosis, a severe disease specially to risk groups such as pregnant women, children, elderly, and immune-compromised adults, leading to mortality rates of 20 to 30% in cases of systemic infection. Despite listeriosis being considered as an infrequent disease, its high severity and mortality and consequent economic losses determine a wide range of studies focusing on L. monocytogenes. The present study aimed the assessment of the occurrence of Listeria spp. and L. monocytogenes in a beef processing plant and beef cuts, and the characterization of the obtained isolates by phenotypic and molecular methodologies. A total of 272 environmental, utensils and beef cuts samples was collected between 2009 and 2012 in a slaughterhouse located in Minas Gerais state, Brazil. Samples were obtained by surface swabbing (400 cm²) and subjected to Listeria spp. and L. monocytogenes detection according protocols ISO 11290-1 and ISO 11290-2. Suspect isolates were subjected to biochemical identification, molecular serotyping, sequencing of atypical PCR products, pulsed field gel electrophoresis (PFGE), detection of virulence genes by PCR (inlA, inlB, inlC, inlJ, plcA, hlyA, actA e iap), and phenotypic tests of antimicrobials resistance. Listeria spp. was identified in 61 samples (22.4%), being L. monocytogenes in 23 (8.5%), L. innocua in 46 (16.9%), and L. seeligeri in 1 (0.37%). A total of 231 isolates was obtained and identified as L. monocytogenes (96), L. innocua (129), and L. seeligeri (6). Among L. monocytogenes isolates, 1/2c or 3c serotype was the most prevalent (74/96), being present in 21 of the 23 positive samples; 15 isolates were identified as serotype 4b atypical and 7 as serotype 1/2b, 3b or 7. PFGE demonstrated the genetic diversity of the isolates and indicated possible contamination routes in the beef processing environment. The isolates were clustered in 6 major groups and 20 pulsetypes after macro-restriction by ApaI and AscI. Isolates with distinct serotypes were grouped in same groups, but never in a same pulsetype. Isolates obtained from distinct samples presented identical genetic profile, as observed in isolates obtained from distinct sampling visits. All tested virulence genes were identified in all L. monocytogenes isolates. Based on PFGE, 20 isolates were selected and tested by phenotypic tests to identify their resistance profiles against 15 antimicrobials; the isolates presented sensitivity to all tested antimicrobials, but 19 isolates were resistant to sulfamethoxazole and 2 also to trimethoprim. Other 2 isolates presented multidrug resistance (gentamicin, tobramycin, clindamycin, trimethoprim, and sulfamethoxazole) and 8 isolates presented intermediary resistance to erythromycin. The obtained data indicate the persistence of L. monocytogenes strains in the beef environment processing of the studied slaughterhouse, possible contamination routes, and the occurrence of multi-drug resistant isolates, to antimicrobials usually considered in the listeriosis treatment.