THE IMPACT OF GASTROINTESTINAL DYSMOTILITY ON THE AERODIGESTIVE MICROBIOME OF PEDIATRIC LUNG TRANSPLANT PATIENTS

Abstract Background Delayed gastric emptying has been associated with increased graft rejection though 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 patients. Methods We prospectively recruited 23 pediatric lung transplant patients 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. Results Lung transplant patients had significantly reduced alpha diversity in gastric and oropharyngeal sites compared to patients with respiratory symptoms. This reduction in alpha diversity was particularly 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). While monocolonies were seen in the lungs of transplant patients, these were not the same microbes seen in the stomach; the microbial overlap between lung and gastric sample within patients was low, and data indicated high individual variation between lung transplant patients. Other contributors to reduced alpha diversity included antibiotics in combination with proton pump inhibitors, particularly in gastric and oropharyngeal samples. Conclusions Lung transplant patients have reduced microbial diversity compared to non-transplant patients in gastric fluid and oropharynx. The decreased alpha diversity in gastric fluid may be associated with dysmotility.