Background:Helicobacter pylori (H. pylori) is a spiral Gram negative bacteria that can transform to the coccoid form in adverse conditions.Objectives:The aim of this study was to determine the in vitro morphological and bactericidal effects of metronidazole, amoxicillin and clarithromycin on H. pylori.Materials and Methods:The standard strain 26695 of H. pylori was cultured on Brucella agar (BA) and the minimum inhibitory concentrations (MICs) of three antibiotics were determined by E-test method. The bacteria were exposed to antibiotics at 1/2 MIC, MIC and 2X MIC concentrations in Brucella broth (BB). Induced coccoid forms were confirmed by Gram staining and light microscopy. The viability of cells as well as the susceptibility of viable coccoids to antibiotics were examined using the flow cytometry method.Results:All of the three antibiotics at sub-MIC induced coccoid forms. The highest rates of coccoids (> 90%) were induced at 0.008 μg/mL concentration (1/2 MIC) of amoxicillin, 72 hours postexposure. Metronidazole and clarithromycin with 1/2 MIC (0.5 and 0.125 µg/mL respectively) induced lower rates of coccoid forms (60% and 40% respectively). Potent bactericidal effects on coccoids were observed with Metronidazole at 2X MIC and clarithromycin at MIC (0.25 µg/mL) (80 - 90%). Amoxicillin with MIC and 2X MIC had no bactericidal effect on coccoid forms.Conclusions:Despite the good in vitro bactericidal effect of amoxicillin on spiral forms of H. pylori, this antibiotic has little effect on induced coccoids that may develop after the inappropriate in vivo antibacterial treatment. Hence, for successful therapy, it is essential not only to eradicate the spiral forms, but to eliminate the viable coccoids.

Helicobacter pylori has grown to colonize inside the stomach of nearly half of the world's population, turning into the most prevalent infections in the universe. Medical care failures noticeably confirm the need for a vaccine to hinder or deal with H. pylori. This review is planned to discuss the most known factors as a vaccine candidate, including single (AhpC, BG, CagA, KatA, Fla, Hsp, HWC, Lpp, LPS, NAP, OMP, OMV, SOD, Tpx, Urease, VacA) and multi-component vaccines. Many promising results in the field of single and multivalent vaccine can be seen, but there is no satisfactory outcome and neither a prophylactic nor a therapeutic vaccine to treat or eradicate the infection in human has been acquired. Hence, selecting suitable antigen is an important factor as an appropriate adjuvant. Taken all together, the development of efficient anti-H. pylori vaccines relies on the fully understanding of the interactions between H. pylori and its host immune system. Therefore, more work should be done on epitope mapping, analysis of molecular structure, and determination of the antigen determinant region as well due to design a vaccine, preferably a multi-component vaccine to elicit specific CD4 T-cell responses that are required for H. pylori vaccine efficacy.

Background:Helicobacter pylori (H. pylori) is one of the most common infectious diseases in the world. It colonizes about 50-60% of the world's population. The estimated prevalence of H. pylori infection is approximately 65% in Iran. Objectives: The aim of the present study was to investigate the antimicrobial resistance of H. pylori to metronidazole, clarithromycin and amoxicillin. Materials and Methods: A total of 110 biopsy specimens were collected from patients with clinical symptoms of gastrointestinal disorders who were referred to the endoscopy unit at Al-Zahra Hospital, Isfahan, Iran. We investigated the frequency of H. pylori resistance to metronidazole, clarithromycin and amoxicillin among 48 positive isolates of H. pylori from the referred patients. After the culture of biopsy specimens and identification of H. pylori strains, susceptibility tests were done using the E test (epsilometer test) Results: The overall rates of resistance to metronidazole, clarithromycin and amoxicillin were 56.3%, 14.6% and 4.2% respectively. In our study, there was a significant correlation between resistance to metronidazole and gender (P < 0.05) but there was no significant correlation between resistance to amoxicillin and clarithromycin and gender (P ˃ 0.05). Conclusions: Information on antibiotic susceptibility profile plays an important role in empiric antibiotic treatment and management of refractive cases. With regards to this study, using metronidazole in the Isfahan region, can lead to eradication failure in clinical therapies due to having the highest rate of resistance but amoxicillin and clarithromycin are prescribed for first and second lines of treatment against H. pylori. Actually, susceptibility testing of H. pylori isolates in different geographical areas is advised because it aids the selection of optimal therapy regimens.

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Backgrounds:Antibiotic resistance is an increasing problem throughout the developed world, and knowledge about different resistance mechanisms is consequential for efficient treatment of bacterial infections. Although metronidazole has been frequently used in treatment regimens for H. pylori infection, but antibiotic resistance is now a major contributing factor in treatment failure. Nevertheless metronidazole has been greatly used as a critical component of combination therapies for H. pylori infection.Objective:This study is trying to describe the mutational mechanisms of metronidazole resistance in H. pylori in our clinical isolates in Isfahanian patients, Iran and compare with the findings of previous studies in world.Materials and Methods:MIC values of metronidazole for H. pylori strains were determined by E- test. Both rdxA and glmM genes used for confirmation of isolates as H. pylori and then amplification of another rdxA oligonucleotide pair was done. Finally, the six resistant strains were sent to sequencing for other processing and further analysis was done by software.Results:The result of six clinical isolates in comparison with 26695, J99 and 69A as a sensitive and resistant reference strains showed plenty of mutations. No frame shift and nonsense mutation was seen in our clinical isolates.Conclusion:An interesting finding in metronidazole-resistant strains in our study was the detection of one mutation not previously described in the literature in the rdxA gene and this W(209)R substitution presumably plays a role in inducing metronidazole resistance.