Research Article: Bacterial Microbiota Profiling in Gastritis without Helicobacter pylori Infection or Non-Steroidal Anti-Inflammatory Drug Use

Date Published: November 24, 2009

Publisher: Public Library of Science

Author(s): Xiao-Xing Li, Grace Lai-Hung Wong, Ka-Fai To, Vincent Wai-Sun Wong, Larry Hin Lai, Dorothy Kai-Lai Chow, James Yun-Wong Lau, Joseph Jao-Yiu Sung, Chunming Ding, Niyaz Ahmed.

Abstract: Recent 16S ribosomal RNA gene (rRNA) molecular profiling of the stomach mucosa revealed a surprising complexity of microbiota. Helicobacter pylori infection and non-steroidal anti-inflammatory drug (NSAID) use are two main contributors to gastritis and peptic ulcer. However, little is known about the association between other members of the stomach microbiota and gastric diseases. In this study, cloning and sequencing of the 16S rRNA was used to profile the stomach microbiota from normal and gastritis patients. One hundred and thirty three phylotypes from eight bacterial phyla were identified. The stomach microbiota was found to be closely adhered to the mucosa. Eleven Streptococcus phylotypes were successfully cultivated from the biopsies. One to two genera represented a majority of clones within any of the identified phyla. We further developed two real-time quantitative PCR assays to quantify the relative abundance of the Firmicutes phylum and the Streptococcus genus. Significantly higher abundance of the Firmicutes phylum and the Streptococcus genus within the Firmicutes phylum was observed in patients with antral gastritis, compared with normal controls. This study suggests that the genus taxon level can largely represent much higher taxa such as the phylum. The clinical relevance and the mechanism underlying the altered microbiota composition in gastritis require further functional studies.

Partial Text: Commensal microbiota is an integral part of a human being [1]. The vast majority of microbes inhabit our gastrointestinal tract, with more than 800 species from nine bacterial and one archaeal phyla. This diverse microbiota contributes to gut maturation [2], [3], [4], host nutrition and pathogen resistance [5]. Microbes also directly interact with human host by regulating intestinal epithelial proliferation, fat storage and inflammatory responses [3], [6], [7]. While some microbes can single-handedly cause serious illness, many chronic conditions are probably due to perturbations of the overall microbiota. For example, allergies and asthma are linked to childhood antibiotic use which may alter intestinal microbiota [8]. Other conditions associated with intestinal microbiota include late-onset autism [9], inflammatory bowel disease [10], and cancer [11].

In this study, we have profiled the bacterial microbiota in the paired gastric biopsies (antrum and body) from normal and antral gastritis patients. All patients are H. pylori negative and without NSAID use. Through broad-range 16S rRNA gene sequencing, we identified 1,223 non-H pylori bacteria clones, similar to a previous study (Bik study, 1,056 non-H pylori bacteria clones) [16]. Although the two studies analyzed two geographically (Hong Kong vs. California) and ethnically (Chinese vs. Caucasian, Hispanics and African American) divergent populations, the overall microbiota complexities are surprisingly similar (Table 3). Both studies identified approximately 130 (133 and 127 for this and the Bik study, respectively) phylotypes from seven to eight phyla. Majority of the clones (77.4% of this study and 79.8% of Bik study) were shared. The two most abundant genera (Streptococcus and Prevotella) were also identical. These two genera represented 40.6% and 41.5% of all clones in this study and the Bik study. Both studies indicated that approximately 200 different phylotypes may be present in the stomach mucosa. Such dramatic similarity between the two studies highlights the selective pressure for the microbiota under the harsh stomach environment. Additionally, we found little difference in bacterial microbiota between the two anatomical sites (antrum and body) in normal patients, despite of the clinical relevance for biopsy sampling at different anatomical sites [31].



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