title: Relapse of type A beta-lactamase-producing Staphylococcus aureus native valve endocarditis during cefazolin therapy: revisiting the issue.
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.
authors.affiliation: Center for the Study of Emerging and Re-emerging Pathogens, Department of Internal Medicine, University of Texas Medical School-Houston, Houston, TX 77030, USA.
authors.forename: Esteban C
authors.initials: EC
authors.lastname: Nannini
authors.forename: Kavindra V
authors.initials: KV
authors.lastname: Singh
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Murray
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002437:Cefazolin / Q000627:therapeutic use*; D004697:Endocarditis, Bacterial / Q000188:drug therapy* / Q000382:microbiology; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D012008:Recurrence; D013203:Staphylococcal Infections / Q000188:drug therapy*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000201:enzymology*; D001618:beta-Lactamases / Q000145:classification / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001618:beta-Lactamases; D002437:Cefazolin