Research Article
Lucas Eduardo Pilon, Livia
Abstract
Identify the causative agents of mastitis present in the mammary glands of primiparous heifers submitted or not to precalving treatment and to determine the in vitro antimicrobial susceptibility profile of the CoNS isolates. Eightyseven animals were studied: Farm (1), 40 heifers, commercial farm, all treated precalving; Farm (2), 18 heifers; Farm (3), 29 animals. On Farms 2 and 3, the animals were divided into precalving treated and untreated groups. The treatments consisting of intramammary antibiotic infusion were administered 60 days before calving to all mammary quarters of each heifer after local antisepsis. Samples were collected during the precalving and calving period, 10 days after calving, and monthly. The results showed a predominance of CoNS during the precalving (28.75%) and calving (1.25%) period on Farm 1. On Farm 2, CoNS predominated during the precalving (88.89%) and calving (60%) period in untreated heifers; in the treated group, the precalving frequency of CoNS was 100%. On Farm 3, coagulase-positive Staphylococci (CoPS) predominated during the precalving and calving period in the untreated group (69.24% and 39.28%, respectively). The antibiogram revealed the following antibiotic resistance profiles: Farm 1 16.98% ampicillin, and 2.83% oxacillin; Farm 2 31.03% penicillin and 17.24% oxacillin, and Farm 3 52.22% penicillin and 13.33% oxacillin. The presence of CoNS in the mammary gland of antibiotic-resistant heifers suggests these animals to be a source of infection in the herd.