Eliminating Staphylococcus aureus Intramammary Infections Using Immune Enhancement and Antibiotic Therapy

Abstract

Staphylococcus aureus intramammary infections are difficult to treat and eliminate from lactating cows. Antibiotic therapy during lactation has often resulted in poor cure rate ofless than 10% and has not been considered economically sound.⁵ Lack of success with antibiotic therapy has been attributed to susceptibility, inaccessibility of the organisms, limited exposure to antibiotic, and poor immune function. The use of multiple antibiotic treatments demonstrate marginal in cure of 38%, with greater responses when milk somatic counts were less than a 1,000,000 cells/ml.¹ Since somatic cell response at time of therapy affects bacteriologic clearance, it might be possible to optimize the animal immune response to assist in this bacteriologic clearance.¹ Staphylococcal vaccines have been most successful when highly encapsulated strains of S. aureus were used.^3,4 These vaccines provide good cross activity between strains and have been used to reduce new infections in heifers. Although these preparations have been successful in preventing new infections, vaccination has not been successful in eliminating existing infections.² Most bacterins do not produce lasting antibody levels, but if timed with antibiotic therapy, the animal's immune status might be optimize to enhance bacteriologic clearance. This clinical trial was designed to incorporate immune enhancement and antibiotic therapy.