Perils of Quinolone Exposure in Cancer Patients: Breakthrough Bacteremia with Multidrug-resistant Organisms

Background: The objective of this study was to determine the effect of antibiotic use (including prophylaxis) on the emergence of multidrug-resistant (MDR) breakthrough bacteremia in cancer patients.

Methods: In this retrospective study, the authors identified all bacteremia episodes from July 2005 to December 2006 at their tertiary cancer center and compared the bacteria types and antimicrobial resistance in isolates from patients who had received antimicrobial agents as therapy or prophylaxis (breakthrough infections) with those from patients who had not received antimicrobial agents (nonbreakthrough bacteremia).

Results: Breakthrough bacteremia was more likely to be associated with MDR Escherichia coli (P = .002), MDR Pseudomonas aeruginosa (P = .02), and vancomycin-resistant enterococci (P = .01). Multivariate analysis revealed that breakthrough bacteremia was associated with hematologic malignancies and neutropenia (odds ratios, 9.9 and 3.0, respectively). Fluoroquinolone use was associated significantly with the emergence of methicillin-resistant Staphylococcus aureus (P = .04), MDR E. coli (P < .001), and MDR P. aeruginosa (P = .05). A strong association was observed between fluoroquinolone use and breakthrough bacteremia in multivariate analysis (odds ratio, 22; P < .001). Patients who had received vancomycin were more likely to have vancomycin-resistant enterococci bloodstream isolates than patients who had not received antibacterial agents (P < .001).

Conclusions: Breakthrough infections were more common in neutropenic patients and in patients who had hematologic malignancies. The isolation of MDR organisms was associated strongly with the use of fluoroquinolones. The current findings demonstrated the importance of using a comprehensive approach to the prevention of MDR bacterial infections, including the initiation of antibiotic stewardship programs.