Disrupted tongue microbiota and detection of nonindigenous bacteria on the day of allogeneic hematopoietic stem cell transplantation

Abstract

Disruption of the intestinal microbiota caused by intensive chemotherapy, irradiation and antibiotics can result in development of severe gut graft-versus-host disease and infectious complications, leading to poorer outcomes among allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Although the oral cavity is also densely colonized by indigenous microorganisms, the bacterial composition in allo-HSCT recipients remains unclear. We determined the tongue microbiota composition of 45 patients with hematological disorders on the day of transplantation and compared them to 164 community-dwelling adults. The V1-V2 regions of the 16S rRNA gene sequences demonstrated that the allo-HSCT recipients had less diverse and distinct microbiota from that of community-dwelling adults. The full-length 16S rRNA gene sequences identified 146 bacterial taxa in the microbiota of allo-HSCT recipients, of which 34 bacterial taxa did not correspond to bacteria primarily inhabiting the oral cavity deposited in the expanded Human Oral Microbiome Database. Notably, the detection of Staphylococcus haemolyticus and/or Ralstonia pickettii was significantly associated with a higher risk of mortality during the follow-up period. These results demonstrate that the oral cavity of allo-HSCT recipients is colonized by a disrupted microbiota on the day of transplantation and suggest that detection of specific nonindigenous taxa could be a predictor of transplant outcome.

Fig 1. Unweighted UniFrac plot of microbiota composition between community-dwelling adults and allo-HSCT patients.

The ellipses cover 67% of the samples belonging to each sample type.

Fig 2. Relative abundances of predominant bacterial genera in the tongue microbiota of community-dwelling adults and allo-HSCT patients.

Only 17 bacterial genera commonly (>98%) present in community-dwelling adults are shown. *P <0.05 in a Wilcoxon rank-sum test followed by P value adjustment for multiple comparison.

Fig 3. Survival plots of the patients with detection or no detection of Staphylococcus haemolyticus and Ralstonia pickettii on the tongue generated by the Kaplan–Meier method.

Significant differences were determined using a log-rank test.