Date of Defense

Fall 12-12-1997

Department

Biological Sciences

First Advisor

Jeffrey L. Watts, Pharmacia & Upjohn

Second Advisor

Silvia Rossbach, Biological Sciences

Third Advisor

Susan F. Kotarsky, Pharmacia & Upjohn

Abstract

Minimum inhibitory concentrations were determined with 700 strains of Staphylococcus aureus isolated from cases of bovine mastitis in nine countries. The countries and number of isolates included England (92), Finland (95), Germany (103), Iceland (22), Ireland (42), Norway (101), Sweden (123), Switzerland (69), and United States (53). The antimicrobial agents tested were ampicillin, oxacillin, cephalothin, ceftiofur, amoxicillin+clavulanate, penicillin+novobiocin, erythromycin, lincomycin, clindamycin, pirlimycin, neomycin, and premafloxacin. The MIC90 for these antimicrobial agents for all strains were 2.0, 1.0, 0.5, 1.0, <= 0.06, 0.13, 0.5, 16.0, 2.0, 1.0, 2.0, and <=0.0078 µg/ml, respectively. Overall, only small variation was observed for lincomycin, clindamycin, and neomycin. Isolation of methicillin-resistant S. aureus was low with only 12 of 700 (1.7%) S. aureus strains resistant to oxacillin. Of the strains tested, 58.3% were positive for β-lactamase production. Of the 257 ampicillin resistant β-lactamase positive S. aureus strains, only 1 strain was resistant to amoxicillin+clavulanate and 2 strains were resistant to penicillin+novobiocin. Erythromycin, clindamycin, and pirlimycin demonstrated good activity against the S. aureus strains, with only 3.4%, 6.1%, and 3.0% resistance to these agents, respectively. Premafloxacin showed excellent activity against all strains tested, with the overall MIC90 of <=0.0078 µg/ml.

Access Setting

Honors Thesis-Campus Only

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