Impact of Gut Colonization by Antibiotic-Resistant Bacteria on the Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation: A Retrospective, Single-Center Study

Gut colonization by antibiotic-resistant bacteria may underlie hard-to-treat systemic infections. There is also accumulating evidence on the immunomodulatory function of gut microbiota after allogeneic stem cell transplantation (alloSCT) and its impact on graft-versus-host disease (GVHD). We investigated the epidemiology and clinical impact of gut colonization after alloSCT and retrospectively analyzed data on 107 alloSCTs performed at a single transplant center. Pretransplant microbiology screening identified colonization in 31% of cases. Colonization had a negative impact on overall survival after alloSCT in univariate (34% versus 74% at 24 months, P < .001) and multivariate (hazard ratio, 3.53; 95% confidence interval, 1.71 to 7.28; P < .001) analyses. Nonrelapse mortality was significantly higher in colonized than in noncolonized patients (42% versus 11% at 24 months, P = .001). Colonized patients more frequently experienced bacteremia (48% versus 24%, P = .01), and more deaths were attributable to infectious causes in the colonized group (42% versus 11% of patients and 67% versus 29% of deaths, P < .05). We observed a significantly higher incidence of grades II to IV acute GVHD in colonized than in noncolonized patients (42% versus 23%, P < .05), especially involving the gastrointestinal system (33% versus 13.5%, P = .07). In summary, we determined that gut colonization by antibiotic-resistant bacteria decreases the overall survival of patients undergoing alloSCT by increasing nonrelapse mortality and the incidences of systemic infection and acute GVHD. (C) 2016 American Society for Blood and Marrow Transplantation.