Epidemiology of bloodstream infections after myeloablative and non-myeloablative allogeneic hematopoietic stem cell transplantation: A single-center cohort study

Background: Patients who undergo allogeneic hematopoietic stem cell transplantation (allo-HSCT) often develop bloodstream infections (BSI). We aimed to describe the etiologies and antibiotic resistance patterns of BSI after allo-HSCT, and, as knowledge about the impact of conditioning regimen is limited, we looked at the incidence, timing, risk factors, and mortality of BSI separately for myeloablative (MA)- and non-myeloablative (NMA)-conditioned patients. Methods: All 460 patients (207 MA- and 253 NMA-conditioned) who underwent their first allo-HSCT at our center from 2008 to 2013 were included in a historical cohort. BSI were registered from initiation of conditioning to day 360 after transplantation. Results: BSI occurred in 34% (95% confidence interval [CI]: 28%, 41%) of MA-conditioned patients and in 17% (95% CI: 12%, 22%) of NMA-conditioned patients. Of all isolates, 68% were gram-positive bacteria (GPB), 23% gram-negative bacteria (GNB), and 9% fungi. The GPB/GNB ratio declined from 2008 to 2014 (P for trend <.01). Of all GNB, 47% were multidrug resistant (MDR), but the proportion declined over the study period. In a multivariate Cox regression model, only acute graft-versus-host disease was associated with a higher hazard of first BSI (hazard ratio 2.50, 95% CI: 1.48, 4.21). Overall 30-day survival after a BSI was higher for MA-conditioned patients than for NMA-conditioned patients (89% vs 74%, P=.04). Conclusion: MA-conditioned patients experience BSI more often than NMA-conditioned patients in the year after allo-HSCT. While BSI are increasingly caused by GNB, the rate of MDR GNB is declining.