Staphylococcus spp. coagulase-negativos em unidades leiteiras: identifica??o fenogenot?pica e prote?mica e an?lise da resist?ncia antimicrobiana.

• Autor(a) principal: Mar?n Rojas, Anna Carolina Coelho
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRRJ
• Texto Completo: https://tede.ufrrj.br/jspui/handle/jspui/2792
• topic: groEL; MALDI-TOF MS; PCR-RFLP; Staphylococcus coagulase-negativos; coagulase-negative staphylococci; Medicina Veterin?ria

Coagulase-negative staphylococci (CNS) have gained attention as etiologic agents of bovine mastitis, a disease which imposes great economic losses to farmers and to the dairy industry. The conventional identification of CNS species, through phenotypic methods is timeconsuming and laborious. Therefore, to overcome limitations of biochemical methods, several genotypic techniques have been proposed. Among them, the PCR-RFLP method using a partial conserved sequence of the groEL gene is a promising alternative, owning to its swiftness, reproducibility and reliability. On the other hand, the proteomic approach, through the MALDI-TOF MS technique, along with its ease of use, provides an accurate and exceedingly faster diagnosis and has been increasingly employed in microbiologic identification. In the field of bovine mastitis, the rational use of antimicrobials depends on the continuous monitoring of resistance towards the drugs most frequently used in bovine herds. Moreover, resistant strains represent a potential hazard to public health. In the genus Staphylococcus, two mechanisms determine resistance to beta-lactams: the beta-lactamase synthesis, coded by the blaZ gene, and the PBP2a production, a modified PBP, coded by the mecA gene. Its expression is worrisome because it grants resistance to all beta-lactams. This report aimed to assess the species identification of 145 CNS isolates from bovine mastitis, through phenotypic and molecular methods. Aditionally, their phenotypic profiles of susceptibility to different antimicrobials were investigated, in particular to beta-lactams, along with the detection of resistance genes involved. S. chromogenes was the species most frequently isolated, with prevalence around 70%. S. xylosus e S. sciuri showed prevalence of 7% each. The biochemical identification showed agreement of 78,6% with the molecular identification. The Cohen?s Kappa coefficient calculated for the identification methods used was 59,7%, which is considered a borderline value between a good and a moderate agreement. The antibiotic resistance was relatively low: 24,8% for penicillin, 9,6% for oxacillin, 6,2% for cefoxitin and 3,4% to erythromycin. It was not observed any resistance against imipenem, cephalotin or to amoxicillin+clavulanate. The mecA gene was detected in 7,6% (11/145) of the isolates, although only two of them showed resistance to cefoxitin in the disk diffusion test. The blaZ gene was found in 44,4% (16/36) of strains resistant to penicillin. It was also detected in 7,3% (8/136) of isolates susceptible to this antibiotic. The significant differences in prevalence, observed among CNS species isolated from subclinical intramammary infections and the distinct distribution of resistance profiles amid them, suggest a clinical and epidemiological impact inherent to each coagulase negative staphylococcal species implicated in bovine mastitis.