Mastitis-causing Escherichia coli: serum sensitivity and susceptibility to selected antibacterials in milk.
A total of 169 Escherichia coli strains were isolated from cows with cases of clinical mastitis. beta-Glucuronidase production, serum sensitivity, and susceptibility to selected antibacterials were analyzed using the fluorometric beta-glucuronidase assay. About 89% (150 of 169) of the isolates tested positive for beta-glucuronidase. Of these isolates producing beta-glucuronidase, 102 (68%) were resistant or moderately resistant to bovine serum. The antibacterial susceptibility of 96 isolates was tested in broth and milk. There was a significant shift from lower fluorometric minimum inhibitory concentration for tetracycline, sulfadoxin-trimethoprim, enrofloxacin, and gentamicin in broth to higher fluorometric minimum inhibitory concentration in milk. Serum sensitivity and susceptibility to tested antibacterials in broth or in milk were not related. Gentamicin and sulfadoxin-trimethoprim seemed to be more potent in mastitic milk than in normal milk, suggesting a possible synergistic effect between these exogenous antibacterials and the indigenous antibacterial agents in mastitic milk.
Fang
W
W
Department of Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Helsinki, Finland.
Pyörälä
S
S
D000667:Ampicillin / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents; D001770:Blood Bactericidal Activity; D002417:Cattle; D000077422:Enrofloxacin; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology*; D004927:Escherichia coli Infections / Q000382:microbiology*; D005260:Female; D024841:Fluoroquinolones; D005839:Gentamicins / Q000494:pharmacology; D005966:Glucuronidase / Q000032:analysis; D008414:Mastitis, Bovine / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000737:chemistry; D015363:Quinolones / Q000494:pharmacology; D013413:Sulfadoxine / Q000494:pharmacology; D013752:Tetracycline / Q000494:pharmacology; D014295:Trimethoprim / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D005839:Gentamicins; D015363:Quinolones; D000077422:Enrofloxacin; D000667:Ampicillin; D013413:Sulfadoxine; D014295:Trimethoprim; D005966:Glucuronidase; D013752:Tetracycline