Ecological analysis of Helicobacter pylori in oral cavities

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A strong association between Helicobacter pylori and chronic active inflammation of the gastric antrum and duodenal ulceration has been recognized. Recently, some molecular ecological studies showed that H.pylori was detected in the dental plaques of patients, suggesting that the human oral cavity represents the natural reservoir of H.pylori. In this study, to estimate the prevalence of H.pylori in human dental plaques, we attempted to measure the population density of H.pylori in the dental plaques of 60 healthy volunteers by the PCR method. Among the subjects, specimens (13%) were found to contain H.pylori DNA.Furthermore, we examined by PCR the existence of H.pylori in dental plaques from various sites in the oral cavity of a gastric H.pylori-positive patient. Of eleven specimens including saliva and 10 dental plaques taken, four specimens of dental plaques were H.pylori-positive.Therefore, it was concluded that human oral cavity is a possible reservoir of H.pylori During the analyses, we found that DNA purification step is critical to detection of H.pylori in dental plaques by our PCR method.To further our understanding of the ecology of H.pylori, we also studied the effect of growth conditions on the growth and bacillary-to-coccoid morphologic conversion of H.pylori using chemostat culture techniques. We have obtained a steady state culture of H.pylori at a relatively low dilution rate (0.04 h-1) under a microaerobi condition. Although the relatively low growth rate, no morphologic conversion was observed in that culture. Further studies are now in progress to ascertain the initiation factors of spherical cell formation under controlled condition in a chemostat.