title: Minimum inhibitory concentrations of equine Corynebacterium pseudotuberculosis isolates (1996-2012).
abstract: BACKGROUND
  Few studies report the minimum inhibitory concentrations for antimicrobials against equine Corynebacterium pseudotuberculosis isolates.
  
  
  OBJECTIVE
  To evaluate trends in the in vitro activities of 20 antimicrobials against equine Corynebacterium pseudotuberculosis isolates from 1996 to 2012 and to determine if a relationship exists between the minimum inhibitory concentration (MIC) and location of the abscess.
  
  
  METHODS
  Corynebacterium pseudotuberculosis isolates from 196 horses with naturally occurring disease.
  
  
  METHODS
  Retrospective and cross-sectional design. Medical records were reviewed to obtain clinical and MIC data. Minimum inhibitory concentrations were determined by the microdilution technique. The MIC results over 3 periods were compared (1996-2001, 2002-2006, 2007-2012).
  
  
  RESULTS
  The MIC90 values for clinically relevant antimicrobials were as follows: chloramphenicol ≤ 4 μg/mL, enrofloxacin ≤ 0.25 μg/mL, gentamicin ≤ 1 μg/mL, penicillin =0.25 μg/mL, rifampin ≤ 1 μg/mL, tetracycline ≤ 2 μg/mL, trimethoprim-sulfamethoxazole (TMS) ≤ 0.5 μg/mL, ceftiofur =2 μg/mL, and doxycycline ≤ 2 μg/mL. There were no significant changes in MIC results over the study period. There was no relationship between MIC patterns and abscess location.
  
  
  CONCLUSIONS
  The MIC50 and MIC90 values of antimicrobials evaluated in this study for equine isolates of C. pseudotuberculosis did not vary over time. Abscess location was not associated with different MIC patterns in cultured isolates. Several commonly used antimicrobials are active in vitro against C. pseudotuberculosis in vitro.
authors.affiliation: School of Veterinary Medicine, W.R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, CA.
authors.forename: D M
authors.initials: DM
authors.lastname: Rhodes
authors.forename: K G
authors.initials: KG
authors.lastname: Magdesian
authors.forename: B A
authors.initials: BA
authors.lastname: Byrne
authors.forename: P H
authors.initials: PH
authors.lastname: Kass
authors.forename: J
authors.initials: J
authors.lastname: Edman
authors.forename: S J
authors.initials: SJ
authors.lastname: Spier
mesh_terms: D000038:Abscess / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003354:Corynebacterium Infections / Q000382:microbiology / Q000662:veterinary*; D016925:Corynebacterium pseudotuberculosis / Q000187:drug effects*; D024881:Drug Resistance, Bacterial; D005260:Female; D006734:Horse Diseases / Q000382:microbiology*; D006736:Horses; D008297:Male; D008826:Microbial Sensitivity Tests; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents
keywords: Antibiotics; Horse; Infection; Susceptibility