Susceptibility to antimicrobial agents among bovine mastitis pathogens isolated from North American dairy cattle, 2002-2010.

Abstract

Approximately 8,000 isolates of Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus aureus, and Escherichia coli, isolated by 25 veterinary laboratories across North America between 2002 and 2010, were tested for in vitro susceptibility to beta-lactam, macrolide, and lincosamide drugs. The minimal inhibitory concentrations (MICs) of the beta-lactam drugs remained low against most of the Gram-positive strains tested, and no substantial changes in the MIC distributions were seen over time. Of the beta-lactam antimicrobial agents tested, only ceftiofur showed good in vitro activity against E. coli. The MICs of the macrolides and lincosamides also remained low against Gram-positive mastitis pathogens. While the MIC values given by 50% of isolates (MIC50) for erythromycin and pirlimycin and the streptococci were all low (≤0.5 µg/ml), the MIC values given by 90% of isolates (MIC90) were higher and more variable, but with no apparent increase over time. Staphylococcus aureus showed little change in erythromycin susceptibility over time, but there may be a small, numerical increase in pirlimycin MIC50 and MIC90 values. Overall, the results suggest that mastitis pathogens in the United States and Canada have not shown any substantial changes in the in vitro susceptibility to beta-lactam, macrolide, and lincosamide drugs tested over the 9 years of the study.

• Authors: Cynthia J Lindeman, Ellen Portis, Lacie Johansen, Lisa M Mullins, Gillian A Stoltman
• Journal: Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc (J Vet Diagn Invest) Vol. 25 Issue 5 Pg. 581-91 (Sep 2013) ISSN: 1943-4936 [Electronic] United States
• PMID: 23907894 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Anti-Bacterial Agents

Topics

• Animals
• Anti-Bacterial Agents (pharmacology)
• Cattle
• Escherichia coli (growth & development)
• Escherichia coli Infections (drug therapy, microbiology, veterinary)
• Female
• Mastitis, Bovine (drug therapy, microbiology)
• Microbial Sensitivity Tests (veterinary)
• North America
• Staphylococcal Infections (drug therapy, microbiology, veterinary)
• Staphylococcus (growth & development)