Abstract
Antibiotic resistance patterns of the major groups of bovine mastitis pathogens (Streptococcus agalactiae, other streptococci, Staphylococcus aureus, and Staphylococcus epidermidis) were examined by determining the minimum inhibitory concentration (MIC) of 13 different antibiotics against bacterial isolates from dairy cattle. The bacterial strains were obtained from milk samples from each cow in 21 New York state dairy herd surveys. In 12 herd surveys (high antibiotic-use group), all 365 cows received antibiotic infusions into the udder at the cessation of each lactation cycle. The 324 animals in the other nine herd surveys (low antibiotic-use group) did not routinely receive antibiotics during the nonlactation period. The MICs from the two groups were compared by calculating for each bacterial group the average MIC, the antibiotic concentration necessary to inhibit 90% of the isolates, and the antibiotic concentration necessary to inhibit 50% of the isolates. Increased resistance to all 13 antibiotics was observed with Streptococcus agalactiae isolates from the high antibiotic use herds. However, there was relatively little difference between the two groups in the resistance patterns of the other bacterial species examined. The most important finding of the study was the identification of a multiple beta-lactam resistance phenotype in Streptococcus agalactiae.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Huber W. G. Antibacterial drug effectiveness against mastitis pathogens. J Am Vet Med Assoc. 1977 May 15;170(10 Pt 2):1182–1184. [PubMed] [Google Scholar]
- Natzke R. P. Elements of mastitis control. J Dairy Sci. 1981 Jun;64(6):1431–1442. doi: 10.3168/jds.S0022-0302(81)82713-0. [DOI] [PubMed] [Google Scholar]
- Smith A., Westgarth D. R., Jones M. R., Neave F. K., Dodd F. H., Brander G. C. Methods of reducing the incidence of udder infection in dry cows. Vet Rec. 1967 Nov 11;81(20):504–510. doi: 10.1136/vr.81.20.504. [DOI] [PubMed] [Google Scholar]