Expressão de genes de Staphylococcus aureus em resposta a concentrações subinibitórias de antibióticos utilizados no tratamento da mastite bovina

• Autor(a) principal: Aguilar, Ananda Pereira
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2452
• topic: Staphylococcus aureus; Mastite bovina; Antibióticos; Expressão gênica; Staphylococcus aureus; Bovine mastitis; Antibiotics; Gene expression; CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA::BIOLOGIA MOLECULAR

Staphylococcus aureus is a major pathogen associated with bovine mastitis. This bacterium produces several virulence factors that confer the ability to adhere and spread in the udder tissue, these factors being regulated by a number of different proteins. During the therapy with antimicrobial agents the bacteria can be exposed to subinhibitory concentrations of antibiotics (subMIC) that can alter the expression of various genes. The objective of this study was to analyze the effect of subinhibitory concentrations of gentamicin and penicillin, commonly used in the treatment of contagious bovine mastitis in the expression of regulators and virulence genes of two genetically distinct S. aureus isolates. We initially determined the minimum inhibitory concentration of antibiotics, which showed similar values for both isolates and subsequently growth curves were built to select the concentrations that were not able to drastically affect the growth rate. Bacterial cultures subjected to 0.25x, 0.12x 0.06xCIM of penicillin and gentamicin were grown to mid-exponential phase and early stationary phase (post-exponential) and used for RNA extraction. Then, we analyzed the expression of the genes sdrC, clfB, hla, hlb, icaD, agrA, saeR, sarA and rot by real time PCR. The expression data were analyzed by the method of Livak (2001) and normalized with the endogenous gene gyrB. The isolates 3993 and 3212 responded differently in their gene expressions when subjected to subinibitory concentrations, which hinders the generalization of the antibiotics effects. SubCIM were able to alter the expression of some regulatory and virulence genes. Concentrations of 0.25x and 0.12xCIM of gentamicin were able to enhance the expression of the regulatory genes sarA and rot, for the bacterial cultures of isolate 3993 obtained in the post-exponential phase. Concentrations of 0.12x and 0.06xCIM of penicillin were able to alter the expression of hla in both growth phases, whereas 0.25xCIM of gentamicin increased the expression of hla in the exponential phase and hlb in the post-exponential phase. However, both antibiotics were not able to alter the expression of the genes sdrC, clfB, icaD, agrA and saeR for the same isolate. For isolate 3212, 0.25xCIM of penicillin modulated significantly clfB gene expression when the culture was obtained in the exponential phase. Thus, the results demonstrated that these antibiotics may induce increased expression of virulence factors and may then lead to an undesirable effect: the progression of the infection.