| Since the discovery of Helicobacter pylon (H.pylori) by Australian scientists Marshall and Warren in 1982, numerous studies have shown that H. pylon is the main cause of chronic active gastritis and peptic ulcer disease. H. pylon is also closely associated with gastric malignancies (gastric cancer, MALT). Both the World Health Organization (WHO) and National Anticancer Union have classified H. pylon as a class one carcinogen, therefore eradication of H. pylon is very important in terms of treatment and prevention of these diseases. Metronidazole is more stable within the stomach and has a stronger anti-H. pylon activity than other antibiotics; it was one of the first antibiotics used to treat H. pylon infection. Metronidazole diffuses into H. pylon and while in the cytoplasm, it is reduced to its active metabolic products by nitroreductase, the reduction products are known to cause DNA damage and hence cell death. With frequent use of metronidazole, drug resistance has become a big concern. Studies have shown that metronidazole resistance rate in the United States and Western Europe is 10-30%; while in China and other developing countries the rate is 70-90%. Thus, it is very important to investigate the mechanism of metronidazole-resistance and research ways to reverse this process. Currently, there are very few studies conducted to investigate metronidazole-resistance in H. pylon. Recent studies noted that Mutations in the rdxA gene have been associated with the acquisition of resistance to metronidazole in H.pyloni[7,16,17]. This gene encodes an NADPH nitroreductase whose expression is necessary for intracellular activation of the drug. Also, Kwon et al[9] discovered that null mutations in ferredoxin-like protein (designated fdxB) and NAD(P)H flavin oxidoreductase (frxA) can induce different degrees of drug-resistance. Experimental results from our prior studies have shown that the proton pump inhibitor Losec [12] and Verapamil[13] can restrict the drug efflux pumps, decrease the excretion of medication, and have a reversal effect on drug-resistant H. pylon; this suggests this is one of the mechanism by which H. pylon become drug-resistant. However, there are no reports about the combination of the outer membrane of H.pylori and metronidazole. Our experiment utilized enzyme linked immunosorbent assay(ELISA) to study the combination of the outer membrane of H.pylori and metronidazole. Also. we purified the associated proteins from metronidazole-sensitive strain and metronidazole-resistant strain and compared the composition of these proteins. Materials & Methods 1. Bacterial strains and growth conditions: drug-sensitive strains of H.pylori used in this study were ATCC43629, (MIC 8ugIml) also a drug-resistant strain was clinically isolated (M~C>25ugIm1). The strains were grown on Pylon plates at 37~C in a microaerobic atmosphere for the first 72 hours, then cultured on Colombia agar plates. 2. Determinations of minimal inhibition concentration(MIC): The MICs were determined by the Paper test 3. The linkage of metronidazole and bovine serum albumin(BSA) was used with the EDC assay 4. The combination of outer membrane of the H. pylon and metronidazole was studied with ELISA: at first, the link of metronidazole and BSA were adhered to the wall of small vessel and washed with phosphate-buffered saline(PBS) for three times after 12 hours. Then, they w...
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