VOGES-PROSKAUER AND COAGULASE TESTS TO THE LABORATORIAL DIAGNOSTIC OF Staphylococcus aureus INCLUDED IN THE EPIDEMIOLOGY OF BOVINE MASTITIS

Abstract

Diagnostic characteristics of acetoin production to the Staphylococcus aureus isolated from milk of mammary quarters of cows with mastitis, orifices of teats and mouthpieces of the liners were studied, in agreement to different coagulation grades presented by strains in the tube coagulase test with rabbit plasma and different rain levels in the environment of the herd. The production of acetoin and the coagulase test were performed after growth on blood agar base supplemented with sheep blood, Gram staining and catalase production. All strains were confirmed by molecular identification at species level by species-specific PCR. Among 329 samples identified, 167 were isolated from milk, 117 from teat orifices and 45 from mouthpieces of the liners. Among these samples, 85.0%, 71.1% and 69.2% strains originated from the milk, mouthpieces and orifices, respectively, presented whole coagulation in the coagulase test. Reduced specificities were obtained to the acetoin production to different coagulation grades on the few rains period as well as on the many rains period. Sensitivities to the acetoin production were higher on the few rains period to all sources and coagulation grades, except to strains from orifices with incomplete coagulation and strains from mouthpieces with complete coagulation. It is recommended the acetoin production test how a good diagnostic strategy to the S. aureus identification, combined with other tests how coagulase, mainly in the milk samples originated from mastitic mammary quarters and on periods with little occurrence of rains.
KEY WORDS: Animal health, bacteriology, diagnosis, milk.