Minimum inhibitory concentrations of cephalosporin compounds and their active metabolites for selected mastitis pathogens.

Abstract

OBJECTIVE:

To compare the minimum inhibitory concentration (MIC) of cephapirin and ceftiofur with MICs of their active metabolites (desacetylcephapirin and desfuroylceftiofur) for selected mastitis pathogens.

SAMPLE:

488 mastitis pathogen isolates from clinically and subclinically affected cows in commercial dairy herds in Wisconsin.

PROCEDURES:

Agar dilution was used to determine MICs for Staphylococcus aureus (n = 98), coagulase-negative staphylococci (99), Streptococcus dysgalactiae (97), Streptococcus uberis (96), and Escherichia coli (98).

RESULTS:

All S aureus isolates were susceptible to cephapirin and ceftiofur. Most coagulase-negative staphylococci were susceptible to cephapirin and ceftiofur. For E coli, 50 (51.0%; cephapirin) and 93 (94.95%; ceftiofur) isolates were susceptible to the parent compounds, but 88 (89.8%) were not inhibited at the maximum concentration of desacetylcephapirin. All S dysgalactiae isolates were susceptible to ceftiofur and cephapirin, and consistent MICs were obtained for all compounds. Most S uberis isolates were susceptible to cephapirin and ceftiofur. Of 98 S aureus isolates classified as susceptible to ceftiofur, 42 (42.9%) and 51 (52%) were categorized as intermediate or resistant to desfuroylceftiofur, respectively. For 99 coagulase-negative staphylococci classified as susceptible to ceftiofur, 45 (45.5%) and 17 (17.2%) isolates were categorized as intermediate or resistant to desfuroylceftiofur, respectively. For all staphylococci and streptococci, 100% agreement in cross-classified susceptibility outcomes was detected between cephapirin and desacetylcephapirin. No E coli isolates were classified as susceptible to desacetylcephapirin.

CONCLUSIONS AND CLINICAL RELEVANCE:

Differences in inhibition between parent compounds and their active metabolites may be responsible for some of the variation between clinical outcomes and results of in vitro susceptibility tests.

• Authors: Cristina S Cortinhas, Leane Oliveira, Carol A Hulland, Marcos V Santos, Pamela L Ruegg
• Journal: American journal of veterinary research (Am J Vet Res) Vol. 74 Issue 5 Pg. 683-90 (May 2013) ISSN: 1943-5681 [Electronic] United States
• PMID: 23627380 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Anti-Bacterial Agents
• Cephalosporins

Topics

• Animals
• Anti-Bacterial Agents (administration & dosage, metabolism, pharmacology)
• Bacteria (classification, drug effects)
• Cattle
• Cephalosporins (administration & dosage, metabolism, pharmacology)
• Drug Resistance, Multiple, Bacterial
• Female
• Mastitis, Bovine (microbiology)
• Microbial Sensitivity Tests
• Species Specificity