| Objective: Lactobacillus is a major constituent of microbiota present widely on the mucosal surface. The physiological and pathological roles of lactobacillus are not well understood.This study is aimed to explorethechanges of lactobacillus in the carcinogenic process of stomach through determination of the prevalence and species distribution of lactobacillus in gastric mucosa from non-atrophic gastritis(NAG), intestinal metaplasia(IM)and gastric cancer(GC).To further clarify roles of lactobacillus in the development of GC, the association between lactobacillus with gastric microbiota and Helicobacter pylori(Hp) infection has been investigated as well.Methods:(1) 160 gastric mucosal biopsies were collected from the antrum of each patient, including 71 NAG, 44 IM and 45 GC. Hp was detected by a pathological method. Lactobacillus was isolated from the gastric mucosa. Bacterial DNA was extracted, and then the 16 S r RNA gene was PCR amplified. The PCR product was directly sequenced. Sequences were analyzed with bioinformaticapproaches. The bacterial species was identified accordingly. The prevalence and species of lactobacillus in gastric mucosa were then determined.(2) The genomic DNA was extracted from gastric antral mucosa biopsies of 130 patients with chronic gastritis. Hp was detected by a pathological method. Real-time quantitative PCR was used to detect lactobacillus and total bacteria qualitatively and quantitatively.Results:(1) Sixty-three lactobacillus strains belonging to eleven species of lactobacillus were isolated by the selective culture. Among them, L. mucosae, L. crispatus and L. oris were first isolated from human stomach. There were nine species in patient with GC, which was more than NAG and IM group.(2) Lactobacillus was present in 62 of 160 patients and the prevalence of Lactobacillus was averaged to 38.4% in human gastric mucosa. The lactobacillus positive rate in NAG, IM and GC group were 24.7%(18/71),38.6%(17/44) and 60.0%(27/45) respectively, showing a gradually increased trend. The prevalence of lactobacillus in gastric cancer was significantly higher than that in NAG and IM(P < 0.05).(3) Of the 160 patients, there are 63 patients were positive for Hp(39.4%). Although lactobacillus positive rate with Hp infection(43.8%) was higher than that without Hp infection(35.4%), the difference was not statistically significant(P > 0.05).(4) Real-time quantitative PCR was carried out using the gastric mucosa genome DNA from 130 NAG. The results showed that the quantity of total bacteria(Log) in gastric mucosa was 7.63 ± 0.70, which meaned that the load of bacteria in gastric mucosa was 4.27×107/μg DNA. The quantity of total bacteria(Log) between lactobacillus positive group and negative group had no significant difference(P > 0.05). The quantity of lactobacillus(Log) in gastric mucosa had no significant association with that of total bacteria(P > 0.05). There was no significant difference in positive rate and quantity of lactobacillus between Hp positive and negative group(P > 0.05).Conclusions:(1) L. mucosae, L. crispatus and L. oris are first isolated from human stomach.(2) The prevalence and species of lactobacillus in gastric mucosa of GC patient are significantly higher than that of NAG and IM group. This indicates that lactobacillus may participate in the occurrence of GC.(3) Lactobacillus in gastric mucosa has no significant effect on Hp and gastric microbiota. This indicates that lactobacillus is involved in the development of GC not though influencing the infection of Hp and gastric microbiota. In the clinic, the efficacy of lactobacillus in improving the Hp eradication rates needs to be reassessed. |
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