IN-VITRO KINETICS OF BACTERICIDAL ACTIVIT Y OF A SOLUTION CONTAINING A COMBINATION OF ANTIBIOTICS IN MILK

The kinetics of bactericidal activity of a combination of neomycin, ba citracin and tetracycline, recommended in the treatment of bovine mast itis, is studied in vitro by replacing the usual culture mediums by UH T semi-skimmed milk. Bactericidal activity is needed against Staphyloc occus aureus and Streptococcus uberis. The antibiotic concentrations t ested were the same as those measured in milk after a treatment perfor med during a pharmacocinetic study. At the concentrations tested the t etracycline dominated the other antibiotics. Bacitracin and neomycin a ppeared to have a clear synergistic action and despite the reduction i n activity linked to the presence of milk, this combination remained e ffective and often bactericidal. The results obtained show that this m ethodological can contribute to a better understanding of the in vivo conditions needed for effective treatment of the mammary gland by a co mbination of locally administered antibiotics.