The impact of gastrointestinal dysmotility on the aerodigestive microbiome of pediatric lung transplant recipients

Delayed gastric emptying has been associated with increased graft rejection, although the mechanism of this association is not known. This study aims to investigate the interrelationship between delays in gastrointestinal motility and the diversity and composition of gastric, oropharyngeal, and lung microbiomes in pediatric lung transplant recipients.We prospectively recruited 23 pediatric lung transplant recipients and 98 pediatric patients with respiratory symptoms undergoing combined endoscopy and bronchoscopy. Gastric, oropharyngeal, and bronchoalveolar lavage samples were collected for 16S sequencing. Gastric samples were also analyzed for bile composition using liquid chromatography.Patients who underwent lung transplantation had significantly reduced alpha diversity in gastric and oropharyngeal sites compared with patients with respiratory symptoms. This reduction in alpha diversity was especially evident in gastric samples in patients with delayed gastric emptying defined as abnormal gastric emptying on nuclear scintigraphy or as an elevation in gastric bile concentration (p ≤ 0.05). Whereas monocolonies were seen in the lungs of patients who underwent transplantation, these were not the same microbes seen in the stomach; the microbial overlap between lung and gastric samples within patients was low, and data indicated high individual variation between lung transplant recipients. Other contributors to reduced alpha diversity included antibiotics in combination with proton pump inhibitors, especially in gastric and oropharyngeal samples.Lung transplant recipients have reduced microbial diversity in gastric fluid (GF) and oropharynx compared with patients who did not undergo lung transplantation. The decreased alpha diversity in GF may be associated with dysmotility.