Molecular typing of fluoroquinolone-resistant and fluoroquinolone-susceptible Escherichia coli isolated from blood of neutropenic cancer patients in a single center.

OBJECTIVE: To investigate the molecular epidemiology of fluoroquinolone-resistant (FQ-R) and fluoroquinolone-susceptible (FQ-S) bacteremic Escherichia coli isolates from neutropenic patients by pulsed-field gel electrophoresis (PFGE) and random amplified polymorphic DNA (RAPD) analysis. METHODS: Nineteen FQ-R and 27 FQ-S isolates of E. coli, obtained from patients on a hematologic ward over a 7-year period, were genotyped by PFGE and RAPD using two different random primers (1247 and 1283). RESULTS: PFGE analysis was able to type all FQ-S isolates and most (17/19, 89%) FQ-R isolates of E. coli. All isolates were genotypically unrelated, with the exception of two indistinguishable FQ-R isolates from different patients in the same period. RAPD analysis typed all isolates, including those FQ-R isolates untypable by PFGE, but was unable to distinguish between some isolates that were different by PFGE. Using primer 1247, RAPD analysis identified six pairs and one triad, while primer 1283 identified seven pairs and one triad of indistinguishable isolates. CONCLUSIONS: No spread of epidemic FQ-R or FQ-S E. coli isolates was documented among neutropenic patients. RAPD analysis is a powerful genotyping method, but appeared to be less reproducible and discriminatory than PFGE for investigating E. coli isolates.