Esophageal Bacteria, GERD, and Barrett's Esophagus

Rather than relying on the conventional methods of culturing bacteria in petri dishes in the laboratory, the researchers decided to mine DNA libraries that have been compiled of bacterial genes. They used a technique called PCR (polymerase chain reaction) to greatly amplify snippets of DNA extracted from biopsies of tissue from the esophagus, and they compared the sequences of the DNA in the biopsies to known bacterial DNA.

The biopsies were taken from four patients who each had a healthy esophagus. Specifically, the biopsies were taken from the distal esophagus, the part closest to the stomach. This area is especially vulnerable to injury due to the backwash of gastric contents that occurs as a consequence of GERD.

The researchers found 95 species of bacteria, and they estimated that they were able to sample 56 to 79 percent of the species in the biopsies. Therefore, even more species may be present. Many of these bacteria resemble garden-variety microorganisms that aren't known to cause disease.

More than 60 percent of the esophageal bacteria were shared among all four individuals, indicating that populations of certain bacterial species appear to be common to all people, according to the study. Although many of the bacteria in the esophagus were highly related to the bacteria found in the mouth, certain bacteria were not known residents of the mouth, says Dr. Pei. This finding suggests that some, if not all, "esophageal bacteria may be unique," he notes.

Importantly, Dr. Pei also directly viewed bacteria colonizing the surface of the esophagus, proving that the bacteria weren't simply traveling through the tube but had taken up residence in the tissue lining it.

Esophageal adenocarcinoma, a kind of cancer, has been increasing rapidly in white men, according to the National Cancer Institute, which sponsored the NYU study. "Animal studies suggest that inflammation and normal bacteria work in concert to cause colon cancer," says Dr. Pei. "Esophageal cancer arises in an area of the esophagus where chronic inflammation is occurring," notes Dr. Pei.

In the next phase of their work, the researchers plan to identify the bacteria in the esophagus in people who have GERD and other esophageal conditions. They suspect that they may find different bacteria in the samples of unhealthy esophageal tissue, which could suggest that microorganisms are playing a role.

"We are operating in the framework of the 'microbiome', a term coined by Nobel Laureate Joshua Lederberg," says Dr. Blaser. "It means that microbes are part of us, part of our identity. They aren't just passengers," he says, " but are, in essence, metabolic and physiologic compartments of the human body."