Endocarditis Due to Methicillin-Resistant Staphylococcus Aureus in Rabbits: Expression of Resistance to Beta-Lactam Antibiotics in Vivo and in Vitro

J Infect Dis. 1984 Jun;149(6):894-903. doi: 10.1093/infdis/149.6.894.


Whether a strain of methicillin-resistant Staphylococcus aureus susceptible to cephalothin by the disk-diffusion method was also susceptible to cephalothin in vivo was evaluated in the rabbit model of endocarditis. Rabbits with aortic-valve endocarditis due to methicillin-resistant S. aureus that were treated for four days with cephalothin had the same numbers of organisms in vegetations as did untreated rabbits. Treatment with cephalothin caused emergence of a highly resistant subpopulation in aortic-valve vegetations. Organisms highly resistant to cephalothin were also highly resistant to nafcillin. Thus broth-dilution and disk-diffusion tests may not predict therapeutic failure for cephalothin against strains of methicillin-resistant S. aureus. Because of cross-resistances among beta-lactam drugs, these strains should be considered uniformly resistant to this general class of antimicrobial agents, regardless of results from these tests.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • Anti-Bacterial Agents / therapeutic use
  • Cephalothin / pharmacology
  • Cephalothin / therapeutic use
  • Endocarditis, Bacterial / drug therapy
  • Endocarditis, Bacterial / microbiology*
  • Methicillin / pharmacology*
  • Microbial Sensitivity Tests
  • Nafcillin / pharmacology
  • Penicillin Resistance
  • Rabbits
  • Staphylococcal Infections / drug therapy
  • Staphylococcal Infections / microbiology*
  • Staphylococcus aureus / drug effects*
  • Vancomycin / pharmacology
  • Vancomycin / therapeutic use


  • Anti-Bacterial Agents
  • Nafcillin
  • Vancomycin
  • Methicillin
  • Cephalothin