1. Prevalence and Characterization of the Cefazolin Inoculum Effect in North American Methicillin-Susceptible Staphylococcus aureus Isolates
- Author
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Tanis C. Dingle, Dulini Gamage, Sara Gomez-Villegas, Blake M. Hanson, Jinnethe Reyes, April Abbott, Carey-Ann D. Burnham, Jennifer Dien Bard, Stephanie Fritz, William R. Miller, Lars F. Westblade, Barbara Zimmer, Cesar A. Arias, and Susan Butler-Wu
- Subjects
Microbiology (medical) ,Methicillin ,Staphylococcus aureus ,Cefazolin ,North America ,Prevalence ,Humans ,Bacteriology ,Bacteremia ,Staphylococcal Infections ,Anti-Bacterial Agents - Abstract
Antistaphylococcal penicillins and cefazolin remain the primary treatments for infections with methicillin-susceptible Staphylococcus aureus (MSSA). The cefazolin inoculum effect (CzIE) causes the cefazolin MIC to be elevated in proportion to the number of bacteria in the inoculum. The objective of this multicenter study was to evaluate the prevalence of the CzIE in North American MSSA isolates. Clinical MSSA isolates from six microbiology laboratories in the United States and one microbiology laboratory in Canada were screened for the CzIE by broth microdilution at a standard inoculum (~5 × 10(5) CFU/mL) and a high inoculum (~5 × 10(7) CFU/mL). Genome sequencing was performed to further characterize the MSSA isolates. The CzIE was present in 57/305 (18.6%) MSSA isolates, ranging from 0% to 27.9% across study sites. More of the CzIE-positive isolates (29.8%) had standard inoculum cefazolin MICs of 1.0 μg/mL than the CzIE-negative isolates did (3.2%) (P
- Published
- 2022