Background: Fluoroquinolone prophylaxis in patients with neutropenia and hematological malignancies is said to be effective on febrile netropenia (FN)-related infection and mortality; however, the emergence of antibiotic resistance has become a concern. Ciprofloxacin and levofloxacin prophylaxis are most commonly recommended. A significant increase in the rate of quinolone-resistant Escherichia coli in fecal flora has been reported following ciprofloxacin prophylaxis. The acquisition of quinolone-resistant E. coli after levofloxacin use has not been evaluated. Methods: We prospectively examined the incidence of quinolone-resistant E. coli isolates recovered from stool cultures before and after levofloxacin prophylaxis in patients with neutropenia from August 2011 to May 2013. Some patients received chemotherapy multiple times. Results: In this trial, 68 patients were registered. Levofloxacin-resistant E. coli isolates were detected from 11 and 13 of all patients before and after the prophylaxis, respectively. However, this was not statistically significant ( P= 0.65). Multiple prophylaxis for sequential chemotherapy did not induce additional quinolone resistance among E. coli isolates. Interestingly, quinolone-resistant E. coli, most of which were extended-spectrum β-lactamase (ESBL) producers, were already detected in approximately 20% of all patients before the initiation of prophylaxis. FN-related bacteremia developed in 2 patients, accompanied by a good prognosis. Conclusions: Levofloxacin prophylaxis for neutropenia did not result in a significant acquisition of quinolone-resistant E. coli. However, we detected previous colonization of quinolone-resistant E. coli before prophylaxis, which possibly reflects the spread of ESBL. The epidemic spread of resistant E. coli as a local factor may influence strategies toward the use of quinolone prophylaxis.
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