Use of In Vitro Susceptibility Data to Direct Antibacterial Therapy of Bovine Respiratory Disease

Abstract

In vitro susceptibility assays, such as the agar diffusion technique and determination of minimum inhibitory concentrations (MIC), can be used to predict antibacterial activity of a drug against specific bacteria isolated from cattle suffering from bovine respiratory disease. Caution should be exercised in interpreting these data because they do not reflect the contribution of the host defenses to antibacterial efficacy nor do they take into account the effects of inflammatory responses and tissue damage on drug activity. Furthermore, the relevance of pharmacokinetic data used to classify the susceptibility of the isolate should be closely examined. Used appropriately, MIC data provided a more quantitative assessment of activity than the agar diffusion technique and can be used together with relevant kinetic data to guide selection of antibacterial agents and dosage regimens.