Antimicrobial sensitivity of aerobic gram-negative rods isolated from bovin udder infections.

Antimicrobial sensitivity of 214 aerobic gram-negative rods recovered from infected bovine mammary glands was determined. Seventeen antimicrobial agents were used. More than 90% of the cultures were sensitive to chloramphenicol, gentamicin, and polymyxin B. These 3 antimicrobials are not approved for infusion into the bovine mammary gland. Escherichia coli was most sensitive to the 17 antimicrobials, and in decreasing sequence, Klebsiella pneumoniae, Citrobacter spp, Enterobacter spp, and Proteus spp were sensitive to fewer antimicrobials. Pseudomonas spp were most resistant.