Related Experiment Video
Updated: Aug 30, 2026

Experimental Endocarditis Model of Methicillin Resistant Staphylococcus aureus (MRSA) in Rat
Published on: June 4, 2012
Relapse of type A beta-lactamase-producing Staphylococcus aureus native valve endocarditis during cefazolin therapy:
Esteban C Nannini1, Kavindra V Singh, Barbara E Murray
1Center for the Study of Emerging and Re-emerging Pathogens, Department of Internal Medicine, University of Texas Medical School-Houston, Houston, TX 77030, USA.
Abstract:
Our experience with a patient with methicillin-susceptible Staphylococcus aureus aortic native valve endocarditis, who had a relapse involving fever and positive blood culture results while receiving cefazolin, led us to evaluate this organism's ability to hydrolyze cefazolin at high inocula, a previously well-documented phenomenon. Analysis of the infecting strain disclosed a high minimum inhibitory concentration of cefazolin when a large inoculum was used, as well as rapid and complete cefazolin degradation, which was associated with regrowth in a time-kill experiment. DNA sequencing of the beta-lactamase gene showed that it was identical to that of the S. aureus type A beta-lactamase, known to efficiently inactivate cefazolin. A word of caution is given regarding the use of this antibiotic for treatment of endocarditis caused by this type of S. aureus isolate.
Related Concept Videos
Endocarditis III: Medical Management
Clinical Significance of Antibiotic Resistance
Endocarditis IV: Nursing Management
Mechanism of Antibiotic Resistance in MRSA
Endocarditis I: Introduction
Mitral Stenosis III: Medical Management