| Backgrounds: H.pylori is a microaerophilic, Gram-negative, spiral bacterium. Since Australian researchers Warren and Marshall successfully isolated H.pylori in gastric mucosa from a patient with gastritis for the first time in 1983, studies on H.pylori have become a hot spot in research fields. A great number of researches have shown the close relationship between H.pylori and the occurrence of diseases in gastro-intestinal tract (GIT) like dyspepsia, chronic gastritis, peptic ulcer, MALT lymphoma and gastric cancer. H.pylori is a chief risk factor of chronic gastritis and peptic ulcer, and also one of the causative factors of gastric adenocarcinoma as well as gastric lymphoma. There is an extremely high infection rate of H.pylori around the world with 30 % to 50 % of adults in the developed countries and 40 % to 80 % in the developing countries. Epidemiological studies in China showed a high result of 40 % to 90 % and an average rate of 59 %. Therefore, the infection of H.pylori has been drawing more and more attention among people. Krajden et al. first isolated H.pylori in dental plaques from a patient of gastritis in 1989, inferring that oral cavity may be an important reservior of H.pylori besides the stomach and Ferguson DA et al. first isolated H.pylori in saliva from one patient of gastritis out of nine in 1993. From then on, many researchers in and out of China demonstrated detections of H.pylori in the oral cavity. As a result, a large number of them showed that there was H.pylori in dental plaques of patients with gastro-intestinal diseases, and H.pylori in the oral cavity had a similarity with gastric H.pylori in morphology, biochemical characteristics and immune characteristics. An obvious homology was also found in H.pylori from the stomach and from the oral cavity in the same patient when gene-typing was done.Studies on the H.pylori in the oral cavity were focused on its relationship with H. pylori in the stomach or its relationship with various kinds of gastric diseases. Besides, its relationship with oral diseases became an investigative hot spot nowadays. H.pylori commonly exists in oral cavities of both healthy individuals and unhealthy individuals. It remains unclear whether it is a kind of conditional pathogenic bacteria in the mouth or not.So far, oral diseases linked with oral H.pylori according to epidemiological information mainly included halitosis, glossitis, periodontitis, burning mouth syndrome, oral lichen planus, recurrent aphthous stomatitis, recurrent oral ulcer and so on.Another important pathogenic function of H.pylori in the oral cavity may rely on its role as an important source of H.pylori for gastro-intestinal tract, as oral cavity served as an important reservoir of H.pylori and H. pylori existing in the oral cavity as well as food, saliva might be sent to gastro-intestinal tract together leading to the occurrence or recurrence of gastro-intestinal diseases which meant oral H.pylori became the key source of gastric H.pylori infection or reinfection after eradication.Objectives: (1)An epidemiological study on the correlation beween oral H.pylori and dental caries was conducted to determine the presence of H.pylori DNA in the dental plaques of examined children aged 3-6 years old with nested PCR and to investigate the relationship between this infection and the occurrence of dental caries or oral hygiene index. (2)The correlation between oral H.pylori and gastric H.pylori was conducted to determine the prevalence of H.pylori in the oral cavity of the studied population with nested PCR, to investigate whether the existence of oral H.pylori can implicate the infection of stomach, and further discuss the relationship between gastric H.pylori infection and the presence of the bacteria in the oral cavity.Methods: (1)214 children from a kindergarten in Guangzhou City of China were evaluated. The children's plaques were assessed by plaque indices of Quigley-Hein. Dental plaque was analysed by nested PCR for two sets of primers directed to the 860-bp fragment of H.pylori genomic DNA. (2)451 dyspeptic patients who were referred for upper gastrointestinal endoscopy in he Center of Digestive Endoscopy of Nanfang Hospital participated in the study. Gastric H.pylori infection was detected by the rapid urease test (RUT) and histological section staining, direct mucosa smear or PCR. And the presence of the bacteria in the oral cavity was observed by nested PCR from dental plaques as in our first epidemiological study. A total of 451 symptomatic subjects (252 males and 199 females; the median age 37 years; range from 12 to 79 years) referred for upper gastrointestinal endoscopy were enrolled in this study.Results: (1)H.pylori was detected in dental plaque samples from 126 children and 70 (55.56%) children with dental caries carried H.pylori in dental plaque. Of these children without infection, only 36 (40.91%) children in 88 suffered dental caries. Besides, the average dental plaque index of 126 H.pylori-positive children was higher than that of 88 children without infection. In the present study there was a significant correlation between H.pylori infection and dental caries (X~2=4.446, P=0.035, OR=1.806) or dental hygiene (Z=-2.873, P=0.004). (2)Oral H.pylori was found in 268 (59.42%) of all 451 individuals in dental plaques, while H.pylori was found in the stomach in 277 (61.42%). In the age group≤29 years, 43 (74.14%) of 58 subjects harboring H.pylori in the dental plaque showed concomitant stomach infection, while 22 (48.89%) of 45 individuals without H.pylori in the dental plaque had H. pylori infection in the stomach (X~2=6.939, P=0.008) . In the age group 30～39 years, 58 (61.70%) of 94 subjects with H.pylori in the dental plaque showed concomitant stomach infection, while 32 (43.24%) of 74 oral-H.pylori negative individuals had H.pylori infection in the stomach (X~2=5.672, P=0.017). 55 (79.71%) of 69 oral-H.pylori positive subjects in the age group 40~49 years had concomitant stomach infection, while 21 (51.22%) of 41 oral-H.pylori negative individuals had gastric H.pylori infection (X~2=9.775, P=0.002) .36 (76.60%) of 47 oral-H.pylori positive subjects in the age group≥50years showed concomitant stomach infection, while 10 (43.48%) of 23 individuals without H.pylori in the dental plaque had H. pylori infection in the stomach (X~2=7.517, P=0.006) . The prevalence of gastric infection was significantly higher in the patients positive for H.pylori in dental plaques than in the patients wihout H.pylori in their dental plaques within all four age groups (P<0.05).Conclusions: (1)There is H.pylori in oral cavities, and the oral cavity may be a potential reservoir for H.pylori besides the stomach. (2)A significant correlation was found beween H.pylori in the oral cavity and the occurrence of dental caries of children, and children with H.pylori in their mouths had a higher prevalence of dental caries than those without H.pylori. H.pylori in dental plaques may play a role in the occurrence of dental caries. (3)Oral H.pylori had a close relationship with oral hygiene, and children who were positive for H.pylori in the oral cavity had a worse oral hygiene than those who were negative for oral H.pylori. The poor oral hygiene may represent a risk factor for H.pylori in the oral cavity. (4)There may be a close relationship between H.pylori in the oral cavity and the bacteria in the stomach. The prevalence of gastric infection was significantly higher in the patients positive for H. pylori in dental plaques than in those negative patients.
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