Is prior antibiotic exposure a risk factor for the development of bacteraemia in bone marrow transplant patients?

Background: Bone marrow transplantation (BMT) is a unique immunosuppressed state, and the consequences of infection are often severe. We hypothesized that disruption of the faecal microbiota (such as with use of broad spectrum antibiotics) may predispose to gastrointestinal related sepsis post bone marrow transplantation. Methods: We reviewed the laboratory data from all BMT patients between January 2016 and August 2018 and recorded the presence of bacteraemia. We matched these patients to controls with no recorded bacteraemia. We then recorded antibiotic exposure in the immediate pre-transplant period. Results: 238 records were reviewed (81 allografts, 157 autografts). We identified 28 patients with bacteraemia from gastrointestinal related pathogens. 28 controls with no positive blood cultures were matched according to the type of BMT. In both groups there were 18 allografts, 12 of which were matched unrelated donors. In the bacteraemic group there were a total of 12 antibiotic episodes (60 days) pre-transplant, compared with 6 (41 days) in the control group. The most common antibiotics used were meropenem (47 days in the bacteraemic group, 24 control) and piperacillin/tazobactan (13 days in the bacteraemic group, 3 control). Conclusion: Our results support the hypothesis that broad spectrum antibiotics pre-transplant may predispose to post-transplant sepsis. Although the small population size limits this study, further studies are necessary to confirm this finding, and to investigate which components of the faecal microbiota are the most important to preserve prior to BMT. This may open the door to novel therapeutics in this patient group, such as faecal microbiota transplant.