Abstract
BackgroundThe distal esophagus harbors a complex bacterial population. We hypothesized that a better understanding of bacterial communities in the esophagus would facilitate understanding of the role of bacteria in esophageal disease. Here, we investigated bacterial composition in the distal esophagus in subjects with a normal esophagus, reflux esophagitis, and Barrett’s esophagus.MethodsTwo biopsy specimens were obtained from the distal esophagus at 1 cm above the gastroesophageal junction under endoscopic examination in 18 patients (6 each with normal esophagus, reflux esophagitis, and Barrett’s esophagus) and used for histological examination and DNA extraction. Fragments of 16S rDNA genes were amplified by PCR using general bacterial primers, and bacterial populations were examined. A third biopsy specimen was taken from the patients with Barrett’s esophagus to histologically confirm the replacement of squamous epithelium with columnar epithelium in the distal esophagus.ResultsEndoscopic diagnoses of normal esophagus, esophagitis, and Barrett’s esophagus were confirmed by histological findings. The total amount of bacterial DNA detected did not significantly differ among groups (p > 0.1). On average, each of the 18 subjects yielded about 350 clones, of which 40 were randomly picked and sequenced. Analysis of 147 16S rDNA sequences from 240 clones of 6 subjects with normal esophagus yielded four phyla, Proteobacteria (49%), Firmicutes (40%), Bacteroidetes (8%), and Actinobacteria (3%). Similar analysis of 139 16S rDNA sequences from 240 clones of 6 patients with reflux esophagitis yielded 6 phyla, Proteobacteria (43%), Firmicutes (33%), Bacteroidetes (10%), Fusobacteria (10%), Actinobacteria (2%), and TM7 (2%). while that of 138 16S rDNA sequences from 240 clones of 6 cases of Barrett’s esophagus yielded 5 phyla, Firmicutes (55%), Proteobacteria (20%), Bacteroidetes (14%), Fusobacteria (9%), and Actinobacteria (2%). Thus, microbial communities differed among patients with a normal esophagus, reflux esophagitis and Barrett’s esophagus.ConclusionsEsophageal bacterial composition differs under conditions of normal esophagus, reflux esophagitis, and Barrett’s esophagus. Diverse bacterial communities may be associated with esophageal disease.
Highlights
The distal esophagus harbors a complex bacterial population
Quantification of bacterial populations Measurement of total bacterial load in mucosal biopsy samples from the distal esophagus in control subjects and patients with reflux esophagitis and Barrett’s esophagus showed high variability among samples, but no significant difference in the total amount of bacterial DNA between the three groups (p > 0.1) (Figure 1)
Two hundred and forty clones (40 clones from each subject) yielded 147 16S rDNA sequences, all of which were classified into 4 phyla
Summary
The distal esophagus harbors a complex bacterial population. We hypothesized that a better understanding of bacterial communities in the esophagus would facilitate understanding of the role of bacteria in esophageal disease. We investigated bacterial composition in the distal esophagus in subjects with a normal esophagus, reflux esophagitis, and Barrett’s esophagus. In western countries, where gastroesophageal reflux disease (GERD) has long been common, the incidence of esophageal adenocarcinoma has increased progressively since the 1970s [1]. The digestive microbiota is a diverse and dynamic system which has developed a synergistic relationship with its host. It plays a crucial role in the development of the host’s innate and adaptive immune system for the maintenance of a normal physiological environment [14,15]. According to an estimate by Pei et al [13], the bacterial biota in the normal distal esophagus is composed of approximately 6 phyla and 140 species. The determined phyla include Firmicutes, Bacteroides, Actinobacteria, Proteobacteria, Fusobacteria, and TM7, of which Firmicutes is the most common, followed by Bacteroidetes
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