title: Relevance of sensitivity testings (MIC) of S. aureus to predict the antibacterial action in milk.
abstract: Bacterial susceptibility testings were carried out in parallel Iso-sensitest broth (ISB) and bovine milk cultures using 16 antibacterials and 4 sensitive strains of mastitic isolates of Staphylococcus aureus. Bacterial activities were analyzed by continuous turbidity monitoring (broth cultures), continuous fluorometric monitoring of the resazurin-reducing redox activity, and by analyzing the triphenyltetrazolium (TTC)-reducing capacity at the end of the incubation period. To obtain an equipotent bacteria-suppressing activity, milk cultures required in general several times more antibiotic than the respective ISB cultures. Antibacterial activities of sulfadoxine-trimethoprim, vancomycin, novobiocin, macrolides, aminoglycosides and oxytetracycline were most effectively suppressed by milk. Aminoglycosides suffered additionally from reduction of oxygen in the incubation environment. The beta-lactams (penicillin G, oxacillin, cephalothin, ceftiofur, ampicillin, ampicillin-clavulanic acid), gentamicin and enrofloxacin showed extremely variable sensitivity results depending on the S. aureus/milk combination.
authors.affiliation: Department of Pharmacology and Toxicology, College of Veterinary Medicine, Helsinki, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Louhi
authors.forename: K
authors.initials: K
authors.lastname: Inkinen
authors.forename: V
authors.initials: V
authors.lastname: Myllys
authors.forename: M
authors.initials: M
authors.lastname: Sandholm
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D005260:Female; D008414:Mastitis, Bovine / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000382:microbiology / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents