infections in our population between 2000 and 2005. Metronidazole resistance is 29.1% inthe treatment naive population compared to 43.2% in those who have had prior therapy,even though none had taken metronidazole for H. pylori eradication purposes. Metronidazoleresistance was more likely to occur in females (35.4% vs 28.5%) than males, probablyreflecting greater use of Metronidazole for gynaecologic infection. In 1997 metronidazoleresistance in the treatment-naive cohort was 27.1%. This reflects the fact that metronidazoleuse in the community is static. Conclusion: This study illustrates that resistance to clarithro-mycin amongst Irish patients infected with H. pylori has increased considerably since 1997.The problems of resistance and poor compliance with treatment are intertwined. The futureof treatment may well lie in greater use of culture and sensitivity analysis prior to treatment.This would promote more accurate treatment and given the latency and long term sequelaeof H. pylori infection, this would appear to be the best approach.

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Quadruple Therapy With Bismuth Subcitrate Potassium, Metronidazole,Tetracycline, and Omeprazole is Superior to Triple Therapy With Omeprazole,Amoxicillin, and Clarithromycin in the Eradication of Helicobacter pyloriPeter Malfertheiner, Francis Megraud, Monique Giguere, Marc Riviere

Background: Helicobacter pylori is associated with a number of conditions including pepticulcer disease (PUD) and dyspeptic symptoms and is the main risk factor for gastric carcinoma.Recommended first-line therapy for H. pylori eradication in Europe is PPI, amoxicillinor metronidazole, and clarithromycin triple therapy given for 7 days. Bismuth-containingquadruple treatments are an alternative first choice. Aim: Compare the rate of H. pylorieradication after quadruple therapy with a single-triple capsule of bismuth subcitrate potas-sium, metronidazole, and tetracycline, given with omeprazole (OBMT) versus omeprazole,amoxicillin, and clarithromycin (OAC) in H. pylori-positive patients with/without presence/history of PUD. Methods: Patients with upper GI symptoms and confirmed H. pylori by C-13 urea breath test (UBT) and rapid urease test with ≥1 of 2 positive results includinghistology and culture were randomized (1:1) to a 10-day course of OBMT or 7-day courseof OAC. Eradication was confirmed by 2 negative UBTs 6 and 10 weeks after treatmentonset. Study was designed for noninferiority, but analysis of superiority was accounted fora priori. Safety and compliance were also assessed. Results: Of 440 patients in the ITTpopulation, 438 received study drug (216 OMBT; 222 OAC), 339 patients were in the PPpopulation. Baseline characteristics including metronidazole (~30%) and clarithromycin(20%) resistance were similar between groups. Compliance was high (>96%) in both groups.Eradication rates were 93.3% (88.5%, 96.5%) with OBMT and 69.6% (61.8%, 76.6%) withOAC in the PP population (P<.001) and 79.8% (73.9%, 84.9%) and 55.4% (48.6%, 62.1%),respectively in the ITT population with imputed data (P<.001). The eradication rate ofOBMT was independent of whether strains were susceptible (95.1%) or resistant (90.5%)to metronidazole at baseline in the PP population (P=.283). The eradication rate of OACwas different in strains resistant to clarithromycin at baseline (8.0%) in the PP populationcompared with susceptible strains (84.9%, P<.001). Both treatments had similar safetyprofiles. About 50% of patients in each group reported an AE with mild to moderate GIcomplaints (dyspepsia, diarrhea, nausea, vomiting) the most frequent (~34% of patients ineach group). Serious AEs were reported in ~2% of patients. Conclusions: H. pylori eradicationrates with OBMT quadruple therapy for 10 days were superior to OAC triple therapy for7 days in patients with/without presence/history of PUD. Safety profiles of the 2 regimenswere similar.

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Induction of H. pylori Resistance to Metronidazole Through EnhancedExpression of a Bacterial Efflux PumpHitoshi Tsugawa, Hidekazu Suzuki, Hiroe Muraoka, Sachiko Suzuki, Kenro Hirata,Juntaro Matsuzaki, Yoshimasa Saito, Toshifumi Hibi

Background.Metronidazole (Mtz) is an important component of H. pylori eradication regi-mens. Mtz enters the cells by diffusion; its antimicrobial toxicity is dependent on thereduction of its nitro group to nitro anion radicals and generation of superoxide radicals.Since NADPH nitroreductase (RdxA) of H. pylori reduces the nitro group of Mtz to activemetabolities that produce DNA strand breaks and oxidative stress, ultimately causing rapidcell death, mutational inactivation of the rdxA gene may be expected to be associated withthe development of resistance to Mtz (Mol. Microbiol. 28:383-93, 1998). However, wepreviously isolated Mtz-resistant strains with an intact RdxA protein (Aliment. Pharmacol.Ther. 24:81-7, 2006), strongly suggesting the existence of a mechanism other than RdxAinactivation for Mtz resistance. The present study was designed to examine the mechanismof acquisition of resistance of H. pylori to Mtz other than RdxA inactivation In Vitro. Methods.Mtz-susceptible H. pylori strains (KS0309, KS0313, KS0317, KS0318, KS0329, KS0330,KS0371, KS0372, KS0381 and KS0391) were used. To induce Mtz resistance In Vitro,the Mtz-susceptible strains were cultured on blood agar plates containing sub-inhibitoryconcentrations of Mtz, with 10 passages every 3 days. The mRNA expression of the genesencoding the efflux pump (HP0605-HP0607, HP0969-HP0971, HP1327-HP1329 andHP1487-HP1489) in the bacteria under Mtz exposure was measured by quantitative RT-PCR, and compared between the susceptible strains and the induced Mtz-resistant strains.Results. Mtz-resistance was induced In Vitro in 10 Mtz-susceptible strains, with MICs rangingfrom 0.5 to 1 μg/mL. After 10 passages of Mtz-susceptible strains on blood agar platescontaining sub-inhibitory concentrations of Mtz, the MICs increased to levels seen for theMtz-resistant strains (MIC>8 μg/mL) in 9 of the strains (8-64 μg/mL). The mRNA expressionlevels of the bacterial efflux pump in the Mtz-susceptible strains were scarcely induced inthe presence of under 0.5 μg/mL Mtz. In contrast, the mRNA expression levels of HP0605and HP1327 in the Mtz-resistant strains increased by about 1.2-1.9 fold (p<0.05) and 1.3-4.6 fold (p<0.05), respectively, in the presence of 0.5 μg/mL Mtz. These results show thatMtz-resistant strains acquire the ability for enhanced expression of HP0605 and HP1327 inresponse to Mtz exposure. Conclusion. Overexpression of two efflux pump genes (HP0605and HP1327) is an initial step in the acquisition of Mtz resistance in H. pylori.

S-33 AGA Abstracts

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Antibiotic Susceptibility Patterns in Helicobacter pylori in 1617 PatientsPerforming an EGDSLuigi Gatta, Nimish B. Vakil, Chiara Ricci, Federico Perna, Ilaria M. Saracino, ValentinaCastelli, Giulia Fiorini, Francesco Di Mario, Dino Vaira

Background: Antimicrobial resistant strains of Helicobacter pylori (H. pylori) have been increas-ing worldwide, and it has been speculated that this may account for progressive decreasein eradication rates reported in the literature. It is therefore clinical and microbiologicallyuseful to periodically survey the prevalence of resistant strains for the most frequently usedantibiotics used in the eradication treatment. Aim: To assess the prevalence of resistantstrains to metronidazole (M), clarithromycin(C), and levofloxacin (L) in a cohort of patientsperforming an EGDS for dyspeptic symptoms in Italy. Methods: Between 2007 and 2009,1617 patients (M/F: 39.5%/60.4%; median age: 52 years; 25th and 75th: 40 and 62 yearsrespectively) underwent upper endoscopy and a biopsy sample was also obtained to performculture and an In Vitro antimicrobial susceptibility testing. Susceptibility testing was per-formed by epsilometer test (Etest) and the following MIC breakpoints were used: resistanceto C (>1 microgram/ml); resistance to M (>8 microgram/ml), and resistance to L (> 1microgram/ml). Results: 773 out of 1617 patients were H. pylori positive (47.8%), andculture was available for the 92% of the infected patients. Resistance to: M was found in61% of the strains, C in 47.1% of the strains, and L in 18.3% of the strains. Double resistanceto: C+M was found in 36.5% of the strains; C+L in 11.3% of the strains; and M+L in 14.7%.10.2% of the strains were resistant to M+C+L. Considering resistance to a single antibiotic,resistance to M was more frequent in women (p<0.001); considering the double resistance,women were also more likely to have resistance to both antibiotics in CM group (p<0.001),CL group (p=0.0005), and ML group (p=0.01); women were finally more probable toharbour strains also resistant to all 3 antibiotics tested (p=0.004). Conclusions: 1. Theprevalence of strains resistant to Clarithromycin and Metronidazole is now very high account-ing for the poor results with conventional triple therapy. 2. Levofloxacin resistance hasreached 18% making it unlikely that this frequently used salvage regimen will be effectivein the future. New treatment regimens and new anti-microbial agents are urgently needed.

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Test, Treat and Re-Test. Who is Best at Checking for Helicobacter pyloriEradication After Apositive Urea Breath Test (UBT), Family Physicians orGastroenterologists?Anthony O'Connor, Niall R. O'Moráin, Mark Dobson, Asghar Qasim, Barbara M. Ryan,Niall Breslin, Humphrey J. O'Connor, Colm A. O'Morain

Introduction: Helicobacter pylori infection causes dyspepsia, peptic ulcers and is a class Icarcinogen. Urea breath test is an accurate and non-invasive test used to diagnose H. pyloriinfection. Current guidelines require re-testing to confirm eradication once infection hasbeen diagnosed and treatment administered. Aims: To assess the adherence of healthcareproviders to ensuring eradication confirmation checks are organised after a positive UBT.Method: 545 patients underwent 13-C UBT testing for the investigation of dyspepsia. Baselineand 15-min gas samples after ingestion of 100 mg 13C-labeled urea were analyzed for excess13CO2/12CO2 ratio (ECR). A cut off point of 4.0 was used to diagnose persistent H. pyloriinfection. 160 (29.8%) were subsequently diagnosed with H. pylori infection. Clinical anddemographic Data was gathered from endoscopy reports, patient charts and pathologyreports. Results: 174 patients had been referred by gastroenterologists for UBT followingdyspepsia consultations without endoscopy, median age 35, 71 males(40.8%). 371 werereferred by family physicians, median age 40, 148 males (39.9%). 35.6% of those referredby gastroenterologists and 26.4% of those referred by family physicians had positive tests.Of 62 patients referred by gastroenterologists who turned out to have a positive UBT 62.9%had eradication checks organised. Of the 98 patients with positive UBT having been referredfrom family physicians 54.6% subsequently had eradication checks organised. Conclusion:Patients referred from gastroenterology clinics with dyspepsia are more likely to have positiveUBTs than those referred from family physicians. There is much failure to adhere to test, treatand re-test policies which has been replicated in other studies, however gastroenterologists aremore likely to comply with these guidelines than family physicians.

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Glutathione Peroxidase-7: An Epigenetically Silenced Gene With DualFunctions in Esophageal AdenocarcinomasDunFa Peng, Tian-Ling Hu, Regine Schneider-Stock, Rupesh Chaturvedi, Keith T. Wilson,Wael M. El-Rifai

Background: Chronic gastroesophageal reflux disease is a major risk factor in the developmentof Barrett's esophagus (BE) and subsequent progression to EACs. Progressive accumulationof reactive oxygen species and subsequent oxidative DNA damage has been reported in BEand EACs. The glutathione peroxidase (GPX) family members protect against oxidative stressby scavenging and inactivating hydrogen and lipid peroxides to water or lipid hydroxyls ina glutathione-dependent reductive reaction. GPX7 is a recently identified GPX with unknownbiological functions. Methods and Results: We examined GPX7 gene promoter methylationusing quantitative Pyro-sequencing technology. None of 37 normal samples, 2 of 11 BE, 7of 11 Barrett's dysplasia (P<.001), and 67 of 106 EACs (P<.001) showed promoter DNAhypermethylation. The DNA hypermethylation correlated with the down-regulation of GPX7expression (P<.01). Three of four EAC cell lines showed methylation of GPX7 and hadstrong expression of DNMT1 and DNMT3b as compared with two BE cell lines. QuantitativeChIP assay of histone modifications along the GPX7 promoter using antibodies specific forH3K9ac, H3K9me, and H3K4me followed by qPCR confirmed the presence of a higherlevel of the repressor histone code (H3K9me) than the activator codes (H3K9ac andH3K4me)in the EAC cell lines. An opposite finding was true in the BE cells. Treatment of EAC cellswith 5-Aza led to demethylation of the GPX7 promoter and re-expression of the GPX7. Were-constituted GPX7 expression in two EAC lines (OE33, FLO-1). Cells stably expressingGPX7 had more than four-fold reduction in growth rate as compared to vector controls.

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