Narrow-spectrum cephalosporin susceptibility testing of Escherichia coli with the BD Phoenix automated system: questionable utility of cephalothin as a predictor of cephalexin susceptibility.
The resistance of Escherichia coli to cephalothin was found to be overestimated when the Phoenix automated susceptibility system was used to determine resistance compared to reference broth microdilution, a finding that jeopardized the use of cephalexin for first-line treatment of urinary tract infections in children. In addition, using broth microdilution, we studied the accuracy of either cephalothin or cefazolin in predicting cephalexin susceptibility. In contrast to the recommendation of the Clinical Laboratory Standards Institute (CLSI), we found that cephalothin is not a reliable predictor of cephalexin susceptibility. Cefazolin performs no better in this role. We suggest that laboratories should consider testing and reporting cefazolin and cephalexin independently, according to clinical need.
Zhang
Sean X
SX
Division of Microbiology, Hospital for Sick Children, Toronto, Ontario, Canada.
Parisian
Fern
F
Yau
Yvonne
Y
Fuller
Jeffrey D
JD
Poutanen
Susan M
SM
Richardson
Susan E
SE
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002506:Cephalexin / Q000494:pharmacology*; D002512:Cephalothin / Q000494:pharmacology*; D003470:Culture Media; D004926:Escherichia coli / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*
D000900:Anti-Bacterial Agents; D003470:Culture Media; D002506:Cephalexin; D002512:Cephalothin