Study of the upper gastrointestinal microbiome has shown that other bacteria besides Helicobacter pylori flourish despite the hostile environment.
Whilst H. pylori is the most studied bacteria in this region with a defined role in inflammation and neoplasia, it is apparent that other bacteria may contribute to UGI disease.
Drs Talley and Walker reviewed current knowledge of bacteria inhabiting the esophagus, stomach and duodenum.
The research team reviewed published studies on the upper gastrointestinal microbiome.
The stomach is a hostile environment for bacteria.
|Eradication of H. pylori is associated with an increase in asthma|
|Alimentary Pharmacology & Therapeutics|
However, recent studies categorising the microbiota have shown surprising results.
H. pylori has been intensively studied since 1984 and recent sequencing analysis of other gastric microbiota shows that H. pylori is not alone.
The team reported that composition can be influenced by acid suppression, gastritis and abundance of H. pylori.
Eradication of H. pylori, whilst decreasing gastric cancer is associated with an increase in asthma, reflux and obesity.
A future approach may be to selectively eradicate bacteria which predispose to inflammation and cancer as opposed to a comprehensive knockout policy.
In the esophagus, viridans streptococci are the most common bacteria influenced by both oral and gastric bacteria.
The team noted that esophagitis and Barrett's oesophagus are characterized by a significant decrease in Gram-positive bacteria, and an increase in Gram-negative bacteria.
The research team described an inverse association of H. pylori and esophageal adenocarcinoma.
The duodenal microbiome has been shown to influence small intestinal bacterial overgrowth, irritable bowel syndrome and celiac disease.
The team noted that numbers of bacteria recoverable by culture are variable in the stomach mucosa and gastric juice, typically 102–104 colony-forming units (CFU)/g or mL and in the esophagus, up to 104 bacteria per mm2 mucosal surface.
In the small bowel, in health, 103 CFU/mL are normal.
Dr Talley and colleague concludes, "This review highlights current knowledge of upper gastrointestinal bacteria and associations with disease."