Cefazolin Surrogacy for Oral Cephalosporin Susceptibility in Urinary Tract Infections
This review examines the evidence behind CLSI's cefazolin surrogate breakpoint, which predicts susceptibility of seven oral cephalosporins for E. coli, K. pneumoniae, and P. mirabilis in uncomplicated UTIs. The authors discuss PK/PD profiles, operational challenges for laboratory implementation, and highlight the limited clinical outcome data supporting this widely adopted testing strategy.
The original study
Cefazolin as a predictor of urinary cephalosporin activity in indicated Enterobacterales.
- Authors
- Bryson AL, Bhalodi A, Liesman RM, Mathers AJ
- Journal
- Journal of clinical microbiology
- Type
- Journal Article, Review
- PMID
- 38457194
Original abstract
Traditionally, cephalothin susceptibility results were used to predict the susceptibility of additional cephalosporins; however, in 2013-2014, the Clinical and Laboratory Standards Institute (CLSI) revisited this practice and determined that cefazolin is a more accurate proxy than cephalothin for uncomplicated urinary tract infections (uUTIs). Therefore, a cefazolin surrogacy breakpoint was established to predict the susceptibility of seven oral cephalosporins for Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis in the context of uUTIs. Clinical microbiology laboratories face several operational challenges when implementing the cefazolin surrogacy breakpoint, which may lead to confusion for the best path forward. Here, we review the historical context and data behind the surrogacy breakpoints, review PK/PD profiles for oral cephalosporins, discuss challenges in deploying the breakpoint, and highlight the limited clinical outcome data in this space.