Emergence of quinolone-resistant Escherichia coli at a comprehensive cancer center
19623 Background: Quinolone prophylaxis is recommended in high-risk neutropenic patients. Although effective in reducing the frequency of febrile episodes and documented gram-negative infections, this approach can lead to the emergence of resistant organisms. Surveillance studies looking for changes in resistance patterns at institutions that care for high-risk patients are also recommended. Methods: Our institution has participated in the meropenem yearly susceptibility test information collection (MYSTIC) program since 2000. The susceptibility of E. coli isolates from our cancer patients to quinolones (ciprofloxacin and levofloxacin) and broad-spectrum agents often used in empiric antimicrobial regimens in such patients, was determined. These studies were conducted by JMI Laboratories, Iowa, USA, and combined results as well as results of each participating institution were provided. CLSI designated breakpoints for susceptibility were used. Ribotyping and PFGE studies were performed on recent isolates. Results: Table 1 documents the declining susceptibility of E. coli isolates to the quinolones. In 2006 only 40.7% were quinolone susceptible compared to 84.2% in 2000 (p = 0.0032). All E. coli isolates remain susceptible to the carbapenems (meropenem, imipenem, ertapenem) and 95.5% remain susceptible to cefepime, ceftazidime, piperacillin-tazobactam, and the aminoglycosides. Twenty-one resistant E. coli isolates underwent ribotyping. Fourteen isolates showed identical ribotype and similar PFGE patterns suggesting the presence of an endemic clone. The other 7 isolates showed variability in their molecular patterns. Conclusions: Quinolone resistance among E. coli strains isolated from cancer patients has increased substantially. Fortunately these isolates remain susceptible to most broad-spectrum beta-lactams and aminoglycosides. Effective infection control methods need to be implemented and enforced in order to reduce the spread of these organisms in high risk patients. No significant financial relationships to disclose. [Table: see text]