Background: The gut microbiota interacts extensively with the host immune system and thus may modify the risk of graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (HSCT). During the post-transplant neutropenic period, the majority of allogeneic HSCT recipients receive empirical broad-spectrum antibiotics for febrile neutropenia. We hypothesized that receipt of an antibiotic regimen with an anaerobic spectrum of activity is associated with a higher risk of grade II-IV acute GVHD than receipt of a non-anaerobic antibiotic regimens.

Methods: In this single-center retrospective cohort study, we evaluated associations between peri-transplant receipt of antibiotics with an anaerobic spectrum of activity and the risk and severity of GVHD among 877 adults who received an allogeneic HSCT between January 1, 2005 and December 31, 2016. We identified 609 patients who developed febrile neutropenia after HSCT and compared GVHD risk and mortality among patients who received anaerobic antibiotics (piperacillin-tazobactam or carbapenems; n=333) to patients who received only antibiotics with minimal activity against anaerobes (aztreonam, ceftazidime, or cefepime; n=276). Antibiotics received by patients between 7 days before and 28 days after allogeneic HSCT and GVHD diagnoses were verified via manual review of medication orders and provider notes in electronic medical records.

Results: Receipt of anaerobic antibiotics was associated with an increased risks of grade II-IV acute GVHD (hazard ratio (HR): 1.41; 95% confidence interval (CI): 1.10-1.79; P=0.01) and acute GVHD mortality (HR: 1.87; 95% CI: 1.13, 3.11; P=0.02). This hazard was primarily associated with acute GVHD of the gut or liver (HR: 1.38; 95% CI: 1.06, 1.79; P=0.02). The association remained with even short (<7 days) courses of anaerobic antibiotics. Anaerobic antibiotic exposure was not associated with acute skin GVHD (HR: 0.97; 95% CI: 0.69, 1.37; P=0.88), chronic GVHD diagnosis (HR: 0.93; 95% CI: 0.70, 1.23; P=0.43), or chronic GVHD mortality (HR: 0.89; 95% CI: 0.44, 1.81; P=0.76).

Conclusions: Receipt of anaerobic antibiotics for febrile neutropenia post-HSCT is associated with an increased risks of acute GVHD of the gut or liver and acute GVHD mortality. Limiting use of antibiotics with an anaerobic spectrum of activity after allogeneic HSCT may reduce acute GVHD incidence and mortality.


Sung:Novartis: Research Funding; Merck: Research Funding; Seres: Research Funding. Martin:Novartis Pharmaceuticals: Other: research support; Jazz Pharmaceuticals: Other: research support.

Author notes


Asterisk with author names denotes non-ASH members.