The rapid detection of cefotaxime-resistant Enterobacteriaceae by HPLC

Abstract

Aim: Antibiotic resistance mediated by extended-spectrum β-lactamases (ESBL) and AmpC β-lactamases is widespread and increasingly common, often rendering empiric antibiotic therapy ineffective. In septicemia, delays in initiating effective antibiotic therapy are associated with worse clinical outcomes. With current phenotypic antimicrobial susceptibility testing methods, there is often a delay of 18-24 h before the susceptibility of an isolate is known. Results: Using an HPLC assay, breakdown of the third-generation cephalosporin cefotaxime by ESBL- and AmpC- β-lactamase-producing organisms could be detected within 90 min with 86.4% sensitivity and 100% specificity; sensitivity for ESBL detection was 100%. Conclusion: This assay could be readily established in any clinical laboratory with an HPLC to rapidly detect ESBL-producing Enterobacteriaceae. Lay abstract In bloodstream infections, early initiation of effective antibiotics is critical. However, with increasing antimicrobial resistance empirical therapy may not be effective. Therefore rapid identification of resistant bacteria is required. Here we describe an assay that can detect resistant gram-negative bacteria within 90 min. Enteric gram-negative bacteria, including Escherichia coli, resistant to the extended-spectrum cephalosporin cefotaxime, could rapidly be identified by using HPLC to detect the breakdown of cefotaxime. This assay could reduce the time to detect resistant bacterial strains by almost a day.