Antimicrobial Susceptibilities of Staphylococcal Species Isolated from Mammary Glands of Unbred and Primigravid Dairy Heifers

Abstract

Staphylococcal isolates from teat canal keratin and mammary secretion samples of unbred and primigravid Jersey heifers were tested in vitro for susceptibility to 12 antimicrobial agents. More than 92% of the 311 isolates were susceptible to all antimicrobial agents tested. Staphylococci other than Staphylococcus aureus demonstrated an overall susceptibility of 98.3% to all antibiotics, and Staphylococcus aureus demonstrated a 97% susceptibility. Across all staphylococcal species, susceptibility of isolates from secretion samples was 98.1%, and susceptibility of isolates from teat canal keratin samples was 93.1%. Differences in susceptibilities were observed among herds.