Challenges in predicting Staphylococcus spp. -lactamic resistance in pet animals

The present work evaluated the species distribution associated with the antimicrobial susceptibility pattern by phenotypic analysis and mec and bla gene detection in 100 Staphylococcus strains from 219 clinical samples from cats and dogs in the state of Rio de Janeiro, Brazil. Oxacillin susceptibility profiles were detected by the Clinical and Laboratory Standards Institute (CLSI) recommended tests. The amplification of the mecA gene was positive in 25% of the Staphylococcus spp. The whole mec complex (mecA-mecI-mecR1) was detected in four phenotypically oxacillin-resistant isolates. The CLSI recommended nitrocefin-based test detected 38% (38/100) β-lactamase producers Staphylococcus strains. Also, 32% (32/100) Staphylococcus spp. strains tested positive for bla genes. The whole bla gene complex, blaZ-blaI-blaR1, was detected in 7.8% (3/38) of the nitrocefinase-positive isolates. β-Lactamases was well spread among the samples and it seems to be a prevalent mechanism in resistant staphylococci strains from pet animals. The mec and bla gene regulatory systems can interfere in expression of resistance mediated by PBPs and β-lactamases, conferring the heterogeneous oxacillin-resistance in Staphylococcus spp. detected by phenotypic tests.