Molecular characterization and antimicrobial susceptibility of Listeria monocytogenes isolated from cattle carcasses in southern Brazil

Listeria monocytogenes ?? um pat??geno de origem alimentar capaz de causar listeriose, tanto em humanos como em animais. A contamina????o por este micro-organismo ?? de dif??cil controle, tendo em vista sua ampla dissemina????o e capacidade fisiol??gica de adapta????o, as quais permitem seu desenvolvimento sob condi????es que usualmente s??o desfavor??veis a outras bact??rias patog??nicas. Assim sendo, esse pat??geno tornou-se motivo de preocupa????o para a ind??stria de alimentos bem como para os consumidores, uma vez que ?? altamente patog??nica, principalmente em rela????o ao grupo de risco, podendo ser fatal em at?? 30% dos casos de listeriose. Embora qualquer isolado de L. monocytogenes possa ser considerado potencialmente patog??nico para humanos, v??rios estudos sugerem que este micro-organismo apresenta patogenicidade heterog??nea, o que torna essencial a caracteriza????o molecular de cada isolado, bem como o conhecimento de sua express??o g??nica, para que possam ser entendidas as diferen??as nos seus mecanismos de patogenicidade.. Em vista do exposto, o presente estudo objetivou verificar a ocorr??ncia de L. monocytogenes em carca??as bovinas abatidas em dois frigor??ficos-matadouros do sul do Rio Grande do Sul e, a partir dos isolados, avaliar sua sensibilidade a antimicrobianos, e realizar a caracteriza????o genot??pica, atrav??s da verifica????o da presen??a de genes de virul??ncia e da express??o da internalina A. A ocorr??ncia de L. monocytogenes nas carca??as foi de 6%, a qual foi detectada no Ponto 1 (ap??s a sangria) e no Ponto 4 (ap??s a lavagem pr??-resfriamento). Foram obtidos 12 isolados, os quais foram avaliados quanto a sensibilidade a 15 antimicrobianos, dos quais 100% mostraram-se sens??veis a maioria dos antibi??ticos testados. Resist??ncia ?? gentamicina (8%), ampicilina (8%), canamicina (8%) e a sulfonamida (83%) foram observadas em parte dos isolados. Suscetibilidade intermedi??ria foi observada para clindamicina (60%) e eritromicina (8%). Quanto aos isolados multirresistentes, dois deles apresentaram resist??ncia a mais de um agente antimicrobiano. Procedeu-se ?? avalia????o da presen??a de genes de virul??ncia (prfA, plcA, plcB, hlya, iap, actA, mpl, inlA, inlC e inlJ) e, atrav??s dos resultados da PCR, foi poss??vel observar que todos os isolados possu??am os genes avaliados, sendo tamb??m confirmada a express??o do gene da internalina A atrav??s da t??cnica de RT-PCR, evidenciando o potencial patog??nico das cepas de L. monocytogenes isoladas de alimentos no sul do Brasil.Listeria monocytogenes is a foodborne pathogen that can cause listeriosis, both in humans and in animals. The contamination by this microorganism is difficult to control, given its wide dissemination and physiological adaptability, which allow its development under conditions which are usually unfavorable to other pathogenic bacteria. Therefore, this pathogen has become of concern to the food industry as well as consumers, since it is highly pathogenic, especially in relation to risk group and may be fatal in 30% of cases of listeriosis. Although any isolate of L. monocytogenes can be considered potentially pathogenic for humans, several studies suggest that this micro-organism has a heterogeneous pathogenicity of the strains, which makes it essential to know the gene expression of the pathogen can be understood that the differences in their virulence mechanisms, and how different potential pathogenicity. The present study aimed to verify the occurrence of. L. monocytogenes in slaughterhouses in southern Rio Grande do Sul, and through the isolates, assess their sensitivity to antibiotics, and perform a genotypic characterization by verifying the presence of virulence genes. L. monocytogenes occured in 6% of the samples, detected after bleeding at the point where the collect was held in the leather of the animal, and point 4 (pre-cooling after washing).Twelve isolates were obtained, which were evaluated for sensibility to 15 antimicrobials, of which 100% were susceptible to most antibiotics tested. Resistance to gentamycin (8%), ampicilin (8%), kanamycin (8%) and sulfonamide (83%) were observed in some isolated of L. monocytogenes. Intermediate susceptibility to clindamycin (60%) and erythromycin (8%) was observed, and multidrug-resistant strains were also observed. Proceeded to evaluate the presence of virulence genes (hlyA, plcA, inlA, inlB, inlC, inlJ, plcB, iap, actA, mpl and PrfA) and, through the results of PCR, it was observed that all isolates possessed the evaluated genes, also confirmed the expression of the gene of internalin A by RT-PCR, showing the potential pathogenic strains of L. monocytogenes isolated from food in southern Brazil