Antibiotics in Hematopoietic Cell Transplantation: Adversaries or Allies?

Rising rates of infections resulting from antibiotic-resistant bacteria (ARB) have led to a worldwide public health crisis calling for a significant improvement in antimicrobial stewardship in all healthcare settings [1]. The burden of antibiotic resistance is high for immunocompromised patients or those who have prolonged exposure to a healthcare setting; particularly vulnerable populations include those who undergo allogeneic hematopoietic stem cell transplantation (allo-HCT) [2]. Immunocompromised patients have higher rates of morbidity and mortality as a result of ARBs [3–6] and colitis resulting from Clostridium difficile (CDI) [7]. This finding is corroborated by the report by Bilinski et al. [8] in this issue of Biology of Blood and Marrow Transplantation in which intestinal colonization of allo-HCT patients with ARBs was associated with higher mortality. In their retrospective analysis, patients were screened for ARBs, including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp., and extended-spectrum beta-lactamase-producing or carbapenamase-producing Enterobacteriaceae, before HCT by rectal swab and culture methods. Within the cohort of 107 allo-HCT patients, gut colonization by ARBs on admission was not only associated with decreased overall survival compared with noncolonized patients (34% versus 74%, respectively, at 24 months, P < .001) but also with an increased incidence of systemic infection, acute graft-versus-host disease (GVHD), and nonrelapse mortality. In a multivariate analysis the only significant predictor for overall survival was gut colonization by ARBs (hazard ratio, 3.53; 95% confidence interval, 1.71 to 7.28). Positive blood cultures were observed more often in colonized patients, and these patients were also more likely to die from infection. Although details of these infectious deaths are not presented, it would be interesting to know which specific systemic infections were found and whether CDI contributed to the increase in mortality, as has been found previously [7]. Assuming that in-hospital use of broad-spectrum antibiotics is a major driver of ARB colonization, the report by Bilinksi et al. supports a growing body of evidence that promotes antimicrobial stewardship practices even—and perhaps especially—in those who are immunocompromised.