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

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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.