Expressão de genes de virulência de Staphylococcus aureus isolados de mastite bovina em resposta a concentrações subinibitórias de antimicrobianos

• Autor(a) principal: Klein, Raphael Contelli
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2426
• topic: Staphylococcus aureus; Mastite bovina; Staphylococcus aureus; Bovine mastitis; CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA::BIOLOGIA MOLECULAR

Staphylococcus aureus is one of the main micro-organisms causing bovine mastitis, a disease that causes the greatest losses in dairy farming worldwide. This pathogen has several virulence factors that contribute to the great genetic diversity observed among isolates and assist in the establishment of infections. In recent years, several studies have shown that the use of antibiotics in subinhibitory concentrations modulates gene expression, influencing the virulence of bacterial pathogens. This study aimed to investigate the effect of subinhibitory concentrations of ampicillin, gentamicin, oxacillin and tylosin, antibiotics used in veterinary formulations for the treatment of mastitis, in the expression of genes from two strains of S. aureus of bovine origin. Initially, we conducted a preliminary investigation of the presence of genes encoding some virulence factors in 85 bacteria isolated from animals with bovine mastitis outbreak. Genes clfB and sdrCDE were the most prevalent, detected in 83.5% and 75.3% of the isolates, respectively. The genetic diversity of isolates, assessed by multiplex PCR, was also high and allowed the discrimination of more than 60 groups. These results guided the choice of S. aureus 4006 and 4125, with genetic similarity of 80% for the later trials. Total RNA from two cultures grown in values equivalent to 0.5X, 0.25X, 0.125X and the minimum inhibitory concentration defined for the four antibiotics was extracted and used in the analysis of real time RT-PCR. The expression of genes spa, clfB, sdrC, fnBP, icaD, icaR, murf and sarA was normalized to the gyrB gene. All antibiotics tested caused alterations in the expression of genes evaluated. The same antibiotics used in different doses, as well as different antibiotics at the same dose, differentially modulate the expression of genes. Only for 4006, the SarA regulatory protein, which regulates the transcription of several virulence factors, was expressed in many different treatments. As for 4125 isolate, the icaD regulator gene was positively influenced when different conditions were tested. In short, the data confirm that genes of S. aureus are expressed differently in response to concentrations of antibiotics below the considered inhibitory concentration and that the variance between strains of S. aureus makes difficult a pattern of expression is extended to all species.