Study On The Modified Bismuth-containing Quadruple Therapy For Helicobacter Pylori Eradication

Part ?High dosage metronidazole and amoxicillin containing bismuth quadruple therapy for Helicobacter pylori treatmentObjective:To evaluate the efficacy and tolerability replacing tetracycline with amoxicillin in bismuth quadruple therapy.Methods:Subjects who were infected with H.pylori and na?ve to treatment were randomly?1:1?assigned to receive a 14-day therapy modified bismuth quadruple therapy:lansoprazole 30 mg,amoxicillin 1 g,bismuth potassium citrate 220 mg?elemental bismuth?,twice a day with metronidazole 400mg 4 times daily?metronidazole group?or clarithromycin 500 mg twice a day?clarithromycin group?.Six weeks after treatment,H.pylori eradication was assessed by¹³C-urea breath test.Antimicrobial susceptibility was assessed by the twofold agar dilution method.Results:Two hundred fifteen subjects were randomized.Both metronidazole and clarithromycin containing regimens achieved high cure rates:per-protocol/intention-to-treat cure rates were:94 of 97?96.9%,95%CI:93.5%-100%?and 93 of 98?94.9%,95%CI:90.5%-99.3%?and 88.9%?95%CI:83.0%-94.8%?and 88.8%?95%CI:82.8%-94.8%?.Amoxicillin,metronidazole and clarithromycin resistant rates were 1.5%,45.5%and 26.5%,respectively.Only clarithromycin resistance reduced treatment success?e.g.,susceptible 98.6%,resistant 76.9%,p=0.001?.Adverse events were more common in the metronidazole group.Conclusion:These results suggest that amoxicillin can substitute for tetracycline in modified 14 day bismuth quadruple therapy as first-line treatment and still overcome metronidazole resistance in areas with high prevalence of metronidazole and clarithromycin resistance.Substitution of clarithromycin for metronidazole was only effective in the presence of susceptible strains.Part?The preliminary study of Helicobacter pylori resistance against levofloxacin by vitro induction and investigate its effect of clarithromycin resistance and mechanismObjective:By in vitro induction of levofloxacin and clarithromycin resistance against H.pylori to investigate whether presence of cross resistance and its possible mechanism.Methods:H.pylori strains were isolated from gastric mucosa of patients,agar dilution method was used to determine its sensitivity to levofloxacin and clarithromycin and then randomly selected 10 strains sensitive bacteria in vitro induce H.pylori resistance against clarithromycin and levofloxacin;after induction,susceptibility test was done to determine their susceptibility to clarithromycin and levofloxacin,genomic DNA were extracted from wild type and induced strains,23S rRNA,gyrA,gyrB gene were amplified by PCR and sequenced.The gene sequences were aligned with standard strain 26695in order to find mutations.Results:10 H.pylori strains,after levofloxacin induced resistance,4 strains of bacteria resistant to levofloxacin,gyrA gene mutations were mainly 87 and 91 loci mutation;3 strains of clarithromycin resistance,among two strains were also resistant to levofloxacin,compared with the wild type strain,resistant bacteria did not find 23S rRNA gene mutations.After resistance induced by clarithromycin,we found no strain resistant to levofloxacin and the resistance related genes also found no mutation,3 strains resistant to clarithromycin,23S rRNA gene mutations were mainly A2143G.Conclusion:In vitro levofloxacin could induce clarithromycin resistance against H.pylori,and 23S rRNA gene did not arise mutation,the activation of efflux pump might be responsible for this phenomenon.And clarithromycin could not induce levofloxacin resistance against H.pylori.Thus in the initial treatment of H.pylori infection,levofloxacin should not be the first choice.Part ? The effect of bile reflux on gastric microbiotaObjective:Bile reflux is one of the common symptoms in the GI department,but the changes of gastric mucosal flora in the course of bile reflux are not clear.In this study,the changes of gastric mucosal flora in patients with bile reflux were analyzed.Methods:Total of 29 patients was recruited including 6 patients with bile reflux remnant gastritis,6 patients with normal appearances of remnant,12 patients with bile reflux gastritis,5 patients with normal appearances of stomach.Genomic DNA was extracted from the mucosal tissue,16S rRNA amplification,cloning and sequenced by 454 pyrosequencing.The structure,diversity and abundance of gastric microbiota were analyzed.Results:216363 high quality reads were captured from the 29 samples.29 phyla and224 genera were identified,in which Proteobacteria,Firmicutes,Actinobacteria,Bacteroidetes and Fusobacteria accounted for more than95%of sequences.There was no difference among groups when We estimated the species richness in four different groups,but the content is different.Proteobacteria was significantly reduced in bile reflux patients,normal gastric microbiota was mainly formed by Proteobacteria and Firmicutes,the diversity of phyla was significantly lower than other groups.We found that the Streptococcus were significantly more abundant in bile reflux and remnant gastritis,while Prevotella oralis was more abundant in bile reflux patients.Conclusion:gastric microbiota harbors a complex microbial community,is mainly composed of Proteobacteria and Firmicutes.And microbiota imbalance happened in bile reflux patients,Proteobacteria was decreased,while Firmicutes,Actinobacteria and Bacteroidetes were enriched,streptococcus and Prevotella oralis were also enriched in bile reflux patients.The flora characteristics as an important biological labels,can be used to predict and monitor host health status.