Validation of a modified Kirby-Bauer disk diffusion method for metronidazole susceptibility testing of Helicobacter pylori.
ABSTRACT Triple antimicrobial therapy that includes metronidazole has been recommended as a first-line therapy for Helicobacter pylori because it has the highest eradication rates. However, resistance in H. pylori to metronidazole has been reported worldwide and its presence may reduce the efficacy of triple therapy. Various methods for testing H. pylori against metronidazole have been used including agar dilution, disk diffusion and the Etest but there has been little standardization of methods. One hundred isolates of H. pylori from different patients were tested for susceptibility to metronidazole by agar dilution, Etest and disk diffusion (5 micrograms disk). The agar dilution results confirmed the MIC susceptibility breakpoint to be < or = 8 micrograms/ml. Using this breakpoint there was close agreement (98%) between Etest and agar dilution results. For susceptible strains, MICs by E-test were generally one twofold dilution lower. Using the error-rate bounded method, agreement between disk diffusion zone diameter and MIC was 98% for agar dilution with breakpoints of > or = 12 mm and < or = 8 micrograms/ml and 100% for Etest with breakpoints of > or = 12 mm and < or = 8 micrograms/ml. The Etest discriminated better than agar dilution between susceptible and resistant strains and was simple to perform. The disk diffusion test is a reliable and cheaper alternative to the Etest with susceptibility being a zone diameter > or = 12 mm with a 5 micrograms disk. The prevalence of metronidazole resistance in this study was 40% by Etest.
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ABSTRACT: Recent studies have shown that the combination of proton pump inhibitor, amoxicillin and clarithromycin is one of the best choices for Helicobacter pylori eradication therapy. However, increasing number of cases of H. pylori infection showing resistance to clarithromycin therapy has been reported and this is currently the main cause of eradication failure. We investigated the annual changes of the antimicrobial susceptibility to clarithromycin, amoxicillin and minocycline during a period of 12 years in Japan. This study comprised 3521 patients (mean age (SD), 55.4 (13.7) years-old, 2467 males and 1054 females) positive for H. pylori as assessed by microaerobic bacterial culture from 1996 through 2008. All patients were previously untreated for H. pylori and were enrolled in the study to assess primary resistance to the three antibiotics. The overall primary resistance to clarithromycin, amoxicillin and minocycline were 16.4%, (577/3521), 0.03% (1/3521) and 0.06% (2/3521), respectively. From 1996 through 2004, the resistance rate to clarithromycin increased gradually to approximately 30% and then it remained without marked fluctuation since 2004. Analysis by gender showed a significant increase (p < .0001) in resistance rate to clarithromycin among females (217/1057, 20.6%) compared to males (360/2467, 14.6%). Analysis by age, disclosed significantly (p < .0001) higher resistance rate to clarithromycin in patients of more than 65-years-old compared to the younger population. The resistance rate of H. pylori infection to clarithromycin in Japan has increased gradually to approximately 30% from 1996 through 2004, and remained unchanged since 2004. Elderly and females were at high risk of having resistance to clarithromycin. Our results suggested that the level of clarithromycin resistance in Japan has now risen to the point where it should no longer be used as empiric therapy.Helicobacter 10/2009; 14(5):86-90. · 3.51 Impact Factor
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ABSTRACT: The heterocyclic analogues of chalcones were synthesized by Claisen Schmidt reaction of (a) benzaldehyde with 2-acetylfurane, 2-acetylpyrrole and 2-acetylthiophene and (b) acetophenone with furfural, thiophene-2-carbaldehyde and pyrrole-2-carbaldehyde. The photolysis of class (a) and (b) chalcones under UV lamp gave different products. The stereoselective photodimerization of 1-(furane-2-yl)-3-phenylprop-2-en-1-one (1), 3-phenyl-1-(1H-pyrrole-2-yl)-prop-2-en-1-one (2) gave β-truxinic type dimers, (3,4-diphenylcyclobutane-1,2-diyl)bis (furane-2-yl methanone) (7), (3,4-diphenylcyclobutane-1,2-diyl)bis ((1H-pyrrol-2-yl) methanone) (8) by syn head-to-head coupling whereas 3-phenyl-1-(thiophen-2-yl)-prop-2-en-1-one (3) gave δ-truxinic type dimers, (3,4-diphenylcyclobutane-1,2-diyl)bis (thiophen-2-yl methanone) (9) by anti head-to-head coupling. The photolytic products of 3-(furane-2-yl)-1-phenylprop-2-en-1-one (4), 1-phenyl-3-(thiophen-2-yl)-prop-2-en-1-one (5) and 1-phenyl-3-(1H-pyrrole-2-yl)- prop-2-en-1-one (6) were identified as corresponding 1,6-di(furane-2-yl)-3,4-diphenylhexa-1,5-diene-3,4-diol (10), 3,4-diphenyl-1,6-di(thiophen-2-yl)hexa-1,5-diene-3,4-diol (11) and 3,4-diphenyl-1,6-di(1H-pyrrol-2-yl)hexa-1,5-diene-3,4-diol (12) pinacol dimers. The antibacterial and antifungal activity of the precursor chalcones and the dimeric products showed antimicrobial activities of different extents with respect to individual compounds. In general, photolysis of heteroaryl chalcones causes the depletion of antimicrobial activity. KeywordsChalcones–Photodimerization–Pinacol dimer–Cyclobutane dimer–Antimicrobial activityMedicinal Chemistry Research 01/2012; · 1.61 Impact Factor
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ABSTRACT: Objective(s) Resistance to antimicrobial agents, particularly metronidazole and clarithromycin, is frequently observed in Helicobacter pylori and may be associated with treatment failure. This resistance rate varies according to the population studied. The aim of this study was to assess the pattern of antimicrobial resistance of H. pylori isolates from dyspeptic patients in Isfahan. Materials and Methods Antral gastric biopsies from 230 dyspeptic patients were cultured. Susceptibility testing to commonly used antibiotics performed on pure cultures of 80 H. pylori-positive isolates by Modified Disk Diffusion Method (MDDM). Genomic DNA extracted and subjected for study of entire genomic pattern using Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR). Results The overall rates of primary resistance were 30.0%, 8.75%, 6.25%, 3.75%, 3.75%, and 2.50% for metronidazole, ciprofloxacin, clarithromycin, azithromycin, tetracycline, and amoxicillin, respectively. Multiple antibiotic resistances were observed in 8 of 27 resistant isolates (29.6%) that mainly were double resistance with the prevalence of 6.25%. No association between antimicrobial resistance and either the gender, age or clinical presentation of the patients were detected. In RAPD-PCR, great diversity observed in 27 resistant strains isolated from different patients and this heterogeneity was not significantly different from susceptible strains. Conclusion Primary H. pylori resistance to metronidazole in our population was lower than the developing world and even other parts of Iran, to ciprofloxacin was considerable in comparison with results in most other countries. Moreover, antibiotic resistance had no effect on genomic pattern of H. pylori isolates. Finally, pretreatment H. pylori isolates susceptibility testing is highly recommended.Iranian Journal of Basic Medical Sciences Iran J Basic Med Sci. 01/2008; 11(11):174-182.