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

Abstract

<bold>Background:</bold> 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 (IR) of GNR bacteremia and FQ-resistant GNR bacteremia in HCT recipients during an era of levofloxacin prophylaxis. <bold>Methods:</bold> We conducted a retrospective cohort study of adults undergoing allogeneic HCT between 2003 and 2012 at the Seattle Cancer Care Alliance (SCCA). Annual trends in the IRs of GNR bacteremia and FQ-resistant GNR bacteremia through 100 days post-transplant 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. <bold>Results:</bold> Of the 2306 patients included in this cohort, 283 (12.3%) had GNR bacteremia. The IRs 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]: 0.98, 1.05 and IRR=1.03; 95% CI: 0.97, 1.10, respectively). FQ-resistant GNR bacteremia was associated with increased mortality compared to FQ-sensitive GNR bacteremia, even after adjustment for underlying disease severity, conditioning regimen, and age at transplant (Hazard ratio=2.31; 95% CI: 1.16, 4.62).<bold> Conclusions:</bold> On average, rates of FQ-resistant GNR bacteremia have not significantly changed at the SCCA over 10 years of FQ prophylaxis, although FQ-resistant GNR bacteremia is associated with increased mortality compared to FQ-sensitive GNR bacteremia.