Genotypic evaluation of antimicrobial resistance in Staphylococcus spp. isolated from bovine clinical mastitis

ABSTRACT Bovine clinical mastitis caused by Staphylococcus spp. is a serious and widespread disease in the world of dairy farming. Antimicrobial therapy is of fundamental importance in the prevention and treatment of infectious mastitis, but the indiscriminate use of antimicrobials acts as a determining factor for the spread of the disease. The present study evaluated the resistance profiles of 57 Staphylococcus spp. isolated from bovine clinical mastitis to beta-lactams and gentamicin, relating characteristics of phenotype (in vitro susceptibility tests) and genotype (detection and expression of genes encoding resistance - mecA, mecALGA251, blaZ, femA, femB, and aacA-aphD - using PCR and RT-PCR, respectively). One or more genes coding for resistance to different antimicrobials were detected in 50 Staphylococcus spp. isolates. The femA and femB genes were the most frequent (75.4% for both). The observed expression of the genes was as follows: blaZ (60%), femA (39.5%), aacA-aphD (50%), femB (32.6%), mecA (8.3%), and mecALGA251 (0%). Considering the relevance of the genus Staphylococcus to bovine mastitis, this study aimed to elucidate aspects regarding the genotypic and phenotypic profiles of these microorganisms so as to contribute to the development of effective strategies for mastitis control.