Gut Microbiota and Intestinal Monodomination as a Predictor for Bacteremia in Allogeneic Hematopoietic Cell Transplant Recipients.

BACKGROUND

Bacteremia is a frequent complication in patients undergoing allogeneic hematopoietic cell transplantation (HCT). Alterations to the gut microbiota after HCT have been associated with adverse outcomes including bacteremia and reduced overall survival. Previous studies suggest that loss of gut bacterial diversity and domination by a single species may predict bloodstream infections, but the degree of domination leading to the optimal positive predictive value (PPV) has not been defined.

METHODS

Stool samples were collected weekly from allogeneic HCT recipients and were analyzed by 16S rRNA gene PCR with sequencing to determine gut microbiota composition and document domination events. Bacteremia events were captured by review of medical records. The PPV for bacteremia of any detection of that species in stool and for domination events at 10%, 30%, and 50% abundance were calculated.

RESULTS

Of 277 HCT recipients, 95 experienced bacteremia, with 130 bacteremia events. Intestinal domination was associated with but not highly predictive for bacteremia, reflected by low PPV. Presence of coagulase-negative Staphylococcus in the gut at >30% relative abundance was associated with increased risk of coagulase-negative Staphylococcus bloodstream infections with PPV of 38%.

CONCLUSIONS

Hematopoietic cell transplantation is associated with significant disruption to the gut microbiota, particularly in patients who subsequently develop bacteremia. Intestinal domination may not be as useful as previously thought given its low PPV for most species implicated in bloodstream infections. The association between gut colonization with Staphylococcus and bacteremia events suggests that the gut may be an under-recognized portal of entry for these organisms in patients after HCT.