Title | Prevalence and Characterization of the Cefazolin Inoculum Effect in North American Methicillin-Susceptible Staphylococcus aureus Isolates. |
Publication Type | Journal Article |
Year of Publication | 2022 |
Authors | Dingle TC, Gamage D, Gomez-Villegas S, Hanson BM, Reyes J, Abbott A, Burnham C-AD, Bard JDien, Fritz S, Miller WR, Westblade LF, Zimmer B, Arias CA, Butler-Wu S |
Corporate Authors | CLSI Cefazolin High Inoculum Ad-Hoc Working Group |
Journal | J Clin Microbiol |
Volume | 60 |
Issue | 7 |
Pagination | e0249521 |
Date Published | 2022 Jul 20 |
ISSN | 1098-660X |
Keywords | Anti-Bacterial Agents, Bacteremia, Cefazolin, Humans, Methicillin, North America, Prevalence, Staphylococcal Infections, Staphylococcus aureus |
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 × 105 CFU/mL) and a high inoculum (~5 × 107 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 < 0.0001). Conversely, more CzIE-negative isolates (39.5%) had standard inoculum MICs of 0.25 μg/mL than the CzIE positive isolates did (5.3%) (P < 0.0001). The most common BlaZ β-lactamase types found in the CzIE-positive strains were type C (53.7%) and type A (44.4%). ST8 and ST30 were the most common sequence types among CzIE-positive isolates and correlated with BlaZ type C and A, respectively. The CzIE was present in up to a quarter of clinical MSSA isolates from North American clinical laboratories. Further studies to determine the impact of the presence of the CzIE on clinical outcomes are needed. |
DOI | 10.1128/jcm.02495-21 |
Alternate Journal | J Clin Microbiol |
PubMed ID | 35578988 |
PubMed Central ID | PMC9297818 |
Grant List | P01 AI152999 / AI / NIAID NIH HHS / United States R21 AI143229 / AI / NIAID NIH HHS / United States R01 AI134637 / AI / NIAID NIH HHS / United States K24 AI121296 / AI / NIAID NIH HHS / United States R01 AI148342 / AI / NIAID NIH HHS / United States K08 AI135093 / AI / NIAID NIH HHS / United States |
Related Faculty:
Lars Westblade, Ph.D.