The present study was aimed to test the in vitro antimicrobial susceptibility using disc diffusion assay and minimum inhibitory concentration (MIC) values, as well as the production of beta-lactamase of 42 strains of Staphylococcus sp. isolated from subclinical mastitis in goats in the semi-arid region of Paraiba state, in Brazil. To this end, 14 samples of negative Staphylococcus chromogenes, 10 S. waneri, 6 S. saprophyticus, 5 S. aureus, 3 S. epidermidis, 2 S. intermedius and 2 Staphylococcus were used. Regarding the in vitro susceptibility, the highest levels of resistance observed concerned penicillin (66.67%) and ampicillin (63.89%), and the greatest sensitivity observed concerned Cefoxitin (97.22%). Multiple resistance to 3 or more antimicrobial drugs was observed in 42.86% of the isolates. Of the total Staphylococcus isolated, 73.81% were positive for the beta-lactamase production test. The minimum inhibitory concentration showed 100% of the samples susceptible to norfloxacin, and the maximum resistance values to the other antimicrobial drugs were 30%. According to the results obtained, it is concluded that, in order to select the most appropriate drug to treat mastitis in goats caused by strains of Staphylococcus, the antimicrobial sensitivity profile of the strain must be known and routine laboratory tests for detecting beta-lactamase should be performed because these enzymes are disseminated both in human and veterinary medicine. The high resistance to penicillin and ampicillin demonstrates the limitation in the use of antibiotics in the treatment of mastitis in goats. Although in the present study the cephalosporines demonstrated a considerable degree of sensitivity, the use of these antimicrobial agents in veterinary medicine becomes a matter of concern due to the incidence of strains that produce betalactamase.
Subclinical mastitis; goats; Staphylococcus ; antimicrobial resistance; Betalactamase; MIC