Incidence rate of fluoroquinolone-resistant gram-negative rod bacteremia among allogeneic hematopoietic cell transplantation patients during an era of levofloxacin prophylaxis.

There are concerns that emerging resistance to fluoroquinolones (FQ) may be leading to increasing rates of gram-negative rod (GNR) bacteremia in hematopoietic cell transplant (HCT) recipients. We set out to describe time trends in the incidence rates of GNR bacteremia and FQ-resistant GNR bacteremia in HCT recipients during an era of levofloxacin prophylaxis. We conducted a longitudinal retrospective study of adults undergoing allogeneic HCT between 2003 and 2012 at the Seattle Cancer Care Alliance (SCCA). Annual trends in the incidence rates of GNR bacteremia and FQ-resistant GNR bacteremia through 100 days after transplantation were assessed using Poisson regression. Cox proportional hazards regression was used to compare 30-day mortality between patients with FQ-resistant and those with FQ-sensitive GNR bacteremia. Of the 2306 patients included in this cohort, 280 (12.1%) had GNR bacteremia. The incidence rates of GNR bacteremia and FQ-resistant GNR bacteremia increased from 2003 to 2009 and decreased afterwards; however, the overall annual trends were not significant (incidence rate ratio [IRR], 1.01; 95% confidence interval [CI], .98 to 1.05; IRR, 1.01; 95% CI, .95 to 1.08, respectively). FQ-resistant GNR bacteremia was associated with increased mortality compared with FQ-sensitive GNR bacteremia, even after adjustment for underlying disease severity, conditioning regimen, and age at transplantation (hazard ratio, 2.11; 95% CI, 1.06 to 4.23). On average, rates of FQ-resistant GNR bacteremia have not significantly changed over 10 years of FQ prophylaxis, although FQ-resistant GNR bacteremia is associated with increased mortality compared with FQ-sensitive GNR bacteremia.