Effect of Metronidazole Resistance on Bacterial Eradication of Helicobacter pylori in Infected Children

A prospective study was performed with 23 Helicobacter pylori-infected children (mean age, 9.5 ± 4.4 years) with clinical symptoms of gastritis and positive results of culture and histologic examination of gastric biopsy specimens to evaluate the influence of antibiotic resistance on eradication. Positive children were treated for 4 weeks with lansoprazole and for 2 weeks with either amoxicillin-metronidazole or spiramycin (a macrolide)-metronidazole. At endoscopy 1 month after the discontinuation of therapy, the eradication rate and improvement of histologically related gastritis were significantly dependent on the susceptibility or the resistance of the infecting organism to metronidazole (83 versus 17% and 88 versus 16.6%, respectively). Pretreatment determination of the susceptibility is appropriate in any anti-H. pylori regimen, including one with metronidazole.     

Quinolone-Based Third-Line Therapy for Helicobacter pylori Eradication

Currently, a standard third-line therapy for Helicobacter pylori (H. pylori) eradication remains to be established. Quinolones show good oral absorption, no major side effects, and marked activity against H. pylori. Several authors have studied quinolone-based third-line therapy and reported encouraging results, with the reported H. pylori cure rates ranging from 60% to 84%. Resistance to quinolones is easily acquired, and the resistance rate is relatively high in countries with a high consumption rate of these drugs. We recently reported a significant difference in the eradication rate obtained between patients infected with gatifloxacin-susceptible and gatifloxacin-resistant H. pylori, suggesting that the selection of quinolones for third-line therapy should be based on the results of drug susceptibility testing. As other alternatives of third-line rescue therapies, rifabutin-based triple therapy, high-dose proton pump inhibitor/amoxicillin therapy and furazolidone-based therapy have been suggested.     

含左氧氟沙星的序贯疗法对根除幽门螺杆菌的疗效观察

目的 探讨含左氧氟沙星的10 d序贯疗法根除幽门螺杆菌(HP)的疗效.方法 将胃镜检查确诊为慢性胃炎和消化性溃疡伴HP阳性的86例患者采用随机数字表法分为两组,每组43例.治疗组前5d给予埃索美拉唑20 ng+阿莫西林1000 mg,2次/d,后5d给予埃索美拉唑20rg2次/d+左氧氟沙星500 mg 1次/d+呋喃唑酮100 mg2次/d;对照组三联疗法为埃索美拉唑20 mg+阿莫西林1000mg+克拉霉素500 mg,2次/d,疗程7d.用药方法均为口服,比较治疗后两组患者的HP根除率.结果 治疗组HP根除率为93.0％ (40/43),对照组为74.4％( 32/43),两组HP根除率差异有统计学意义(x2 =4.18,P＜0.05).结论 含左氧氟沙星的10 d序贯疗法治疗HP感染具有较高的根除率.     

含左氧氟沙星序贯疗法根除幽门螺杆菌的疗效观察

目的观察由雷贝拉唑、左氧氟沙星、阿莫西林、呋喃唑酮组成的10日序贯疗法根除幽门螺杆菌（Hp）的疗效。方法将经胃镜检查确诊为慢性胃炎和消化性溃疡且Hp阳性的患者88例随机分为两组,治疗组（44例）方案为前5d给予雷贝拉唑、阿莫西林,后5d给予雷贝拉唑、左氧氟沙星、呋喃唑酮;对照组（44例）三联疗法为雷贝拉唑、阿莫西林、克拉霉素,疗程7d。比较治疗后两组患者Hp根除率。结果治疗组Hp根除率为90．9％,对照组为75．0％,两组患者Hp根除率间差异有统计学意义（P〈0．05）。结论以雷贝拉唑、左氧氟沙星等组成的10日序贯疗法治疗Hp感染具有较高的根除率。     

A Redox Basis for Metronidazole Resistance in Helicobacter pylori

Metronidazole resistance in Helicobacter pylori has been attributed to mutations in rdxA or frxA. Insufficient data correlating RdxA and/or FrxA with the resistant phenotype, and the emergence of resistant strains with no mutations in either rdxA or frxA, indicated that the molecular basis of H. pylori resistance to metronidazole required further characterization. The rdxA and frxA genes of four matched pairs of metronidazole-susceptible and -resistant strains were sequenced. The resistant strains had mutations in either rdxA, frxA, neither gene, or both genes. The reduction rates of five substrates suggested that metabolic differences between susceptible and resistant strains cannot be explained only by mutations in rdxA and/or frxA. A more global approach to understanding the resistance phenotype was taken by employing two-dimensional gel electrophoresis combined with tandem mass spectrometry analyses to identify proteins differentially expressed by the matched pair of strains with no mutations in rdxA or frxA. Proteins involved in the oxireduction of ferredoxin were downregulated in the resistant strain. Other redox enzymes, such as thioredoxin reductase, alkyl hydroperoxide reductase, and superoxide dismutase, showed a pI change in the resistant strain. The data suggested that metronidazole resistance involved more complex metabolic changes than specific gene mutations, and they provided evidence of a role for the intracellular redox potential in the development of resistance.Metronidazole (Mtr) is an important component of therapeutic regimens that currently are used to treat many microbial infections. Metronidazole is considered a prodrug whose uptake and activation requires intracellular reduction, resulting in the production of cytotoxic short-lived radicals and other reactive species (29). 5-Nitroimidazole is activated via interactions with redox systems capable of reducing the low-potential (−415 mV) nitro group in position 5 of the imidazole ring (29). This property makes metronidazole effective against organisms in a low-intracellular-redox state, such as anaerobic bacteria and protozoa, as well as some microaerophiles, such as Campylobacter spp. and Helicobacter pylori (16).Helicobacter pylori is found in the gastric mucous layer or adhering to the epithelial lining of the human stomach and is one of the most prevalent infections in humans (1, 19, 39). The frequent use of metronidazole has resulted in increased resistance to the antibiotic by H. pylori. The emergence of resistant isolates that do not respond to the drug fostered an interest in understanding the primary causes of resistance to metronidazole in this bacterium. Extensive investigations of H. pylori established that the main causes of metronidazole resistance are mutations in the gene rdxA or frxA (6, 7, 14, 15). However, insufficient data correlating the oxygen-insensitive nitroreductase RdxA and/or the NAD(P)H flavin oxidoreductase FrxA with the resistant phenotype and the fact that a small percentage of resistant strains do not have mutations in either rdxA or frxA indicated that the molecular basis of H. pylori resistance to Mtr has not been characterized completely.Early studies showed that the oxygen tension has a large impact on the resistance of H. pylori to Mtr (23, 31-33), and several investigations have linked the activities of specific oxidoreductases to the Mtr-susceptible phenotype of the bacterium (9, 23, 36). Three disulfide reduction activities, which use dithiobis-2-nitrobenzoic acid (DTNB), oxidized glutathione (GSSG) and NADH, or ferredoxin (Fdx) and NADH as substrates, were identified in H. pylori (12). Metronidazole inhibited disulfide reduction competitively in each of the three activities, and the measured inhibition constants of Mtr for the reduction of different substrates indicated that the effects of Mtr were stronger in susceptible strains than in resistant ones (12). The presence of DTNB, GSSG, or Fdx inhibited Mtr reduction in situ, indicating that these substrates competed with Mtr as acceptors in redox reactions catalyzed by the corresponding disulfide reductases and suggesting that the enzymes participated in the reduction of Mtr (12). These results indicated a possible role in Mtr activation by enzymes catalyzing redox reactions that modulate the intracellular redox status, and that in metronidazole-susceptible strains, the cellular machinery regulating the redox status maintains an intracellular potential sufficiently low to activate metronidazole-reducing pathways (12).In this study, four matched pairs of susceptible and resistant strains with different mutations in their rdxA and frxA genes were investigated. The redox state of the cells and the metabolic reduction of five substrates were measured. A more global approach was required to understand the resistant phenotype; thus, changes in the proteome of a matched pair of strains with no mutations in rdxA or frxA and changes induced in the proteome of the Mtr-resistant strain subjected to Mtr were investigated using two-dimensional gel electrophoresis and mass spectrometry (MS).     

New Options in Eradication of Helicobacter pylori

Better treatment options to eradicate Helicobacter pylori are needed, while we await a possible effective vaccine against the world's most common infection. The goals of therapy for H. pylori infection should be an effective and low-cost therapy with a low frequency of side-effects. The currently available eradication regimens are cumbersome, which can lead to a reduction of compliance and a lower efficacy. More recent studies have shown, however, that the duration of antimicrobial treatment may be shortened, which also makes the treatment more cost-effective and more tolerable. At this point it seems relevant to treat H. pylori infection first with some antisecretory modification of triple therapy, while the therapeutic failures can be treated with other more relevant and suitable alternatives. Metronidazole is still a cornerstone of triple therapy and the more expensive clarithromycin is an alternative second-line treatment. Time will show the effectiveness and suitability of the latest topical 1-day treatments.     

Eradication of Helicobacter pylori in Japan]

Twenty five years has passed since the re-discovery of Helicobacter pylori. Many people have studied on this organism since that time. Some mechanisms about gastric mucosal inflammation have been clarified, and pathogenesis of peptic ulcer formation and gastric cancer have been solved. H. pylori infection is related to chronic gastritis, peptic ulcer, gastric carcinoma, and MALToma. In 1998, it was reported that gastric cancer occurred in H. pylori infected mongolian gerbils. In Japan, the prevalence of peptic ulcer and gastric cancer is very high. Therefore, the treatment for H. pylori infection is necessary to prevent occurrence of these diseases. To treat H. pylori infection, various regimen have been tried. Triple therapy with PPI and two antibiotics is recommended for cure of H. pylori infection in European and US guidelines. Some guidelines for management of H. pylori infection and regimen were shown in this part.     

Nitazoxanide in treatment of Helicobacter pylori: a clinical and in vitro study

Nitazoxanide (NTZ) is an antibiotic with microbiological characteristics similar to those of metronidazole but without an apparent problem of resistance. The aim of this study was the prospective evaluation of NTZ given as a single agent in the treatment of Helicobacter pylori infection. Twenty culture-positive patients with dyspepsia who had previously failed at least one course of H. pylori eradication therapy were enrolled. Subjects received 1 g of NTZ twice daily for 10 days. The safety and tolerability of the drug were assessed by physical examination, monitoring of adverse events, and clinical laboratory evaluation. Urea breath tests (UBTs) were performed 6 weeks posttreatment. H. pylori was isolated from UBT-positive patients by the string test or endoscopy with biopsy, and the MICs for these isolates were compared to those for isolates obtained pretherapy. The levels of tizoxanide, the active deacylated derivative of NTZ, were measured in blood, saliva, and tissue from two patients during treatment. The UBT results were positive for all 20 patients after completion of NTZ therapy. The MIC results demonstrated that the NTZ susceptibilities of none of the strains isolated from the patients posttherapy had changed significantly. No major adverse reactions were observed, but frequent minor side effects were observed. In conclusion, NTZ did not eradicate H. pylori when it was given as a single agent.     

Eradication therapy of Helicobacter pylori for elderly patients in Japan

In Japan, an eradication therapy of Helicobacter pylori(H. pylori) for peptic ulcers of stomach and duodenum was approved by a health insurance since November 1, 2000. A method of an eradication therapy is as follows. Adult patients are received lansoprazole 30 mg, amoxicillin 750 mg, clarithromycin 200-400 mg at the same time twice daily for seven days. This therapy is based on a guideline of a Japanese association of Helicobacter Research. Many elderly patients have complications such as hypertension, cerebral vascular disturbance, heart failure and so on. Moreover, they often take a several medicine including NSAIDs(non-steroidal anti-inflammatory drugs). Therefore, you should pay attention especially to interaction of drugs when planning an eradication therapy of H. pylori for elderly patients.     

Clarithromycin Resistance and Eradication of Helicobacter pylori in Children

Outcome of Helicobacter pylori infection was analyzed in 61 children treated with a triple therapy including clarithromycin. Bacterial eradication was obtained in all children with clarithromycin-susceptible strains but not in children with clarithromycin-resistant ones (P = 0.0001). H. pylori antimicrobial susceptibility is mandatory before choosing a treatment, and clarithromycin should be avoided in case of resistance.     

Eradication of Helicobacter pylori: recent advances in treatment

Helicobacter pylori plays a key role in dyspepsia, peptic ulcer disease, and gastric neoplasia and eradication of the infection has become an important treatment goal in clinical practice. Seven-day proton-pump inhibitor-amoxicillin-clarithromycin triple therapy is the current first-line therapy for H. pylori but eradication rates are compromised by poor compliance and antibiotic resistance. Ten-day sequential treatment may emerge as an alternative first-line therapy. Bismuth-based quadruple therapy is the second-line regimen of choice. Antimicrobial sensitivity testing is not recommended in the routine management of H. pylori infection. Novel triple-therapy regimens containing rifabutin, levofloxacin, or furazolidone may be useful alternatives as second- or third-line therapy.     

Risk of Development of In Vitro Resistance to Amoxicillin, Clarithromycin, and Metronidazole in Helicobacter pylori

We have studied initial killing, morphological alterations, the frequency of occurrence, and the selective growth of resistant subpopulations of Helicobacter pylori during exposure to amoxicillin, clarithromycin, or metronidazole by bioluminescence assay of intracellular ATP levels, microscopy, and a viable count assay. We found an induction of spheroplasts and a decrease in intracellular ATP levels after 21 h of exposure to high concentrations of amoxicillin. During clarithromycin exposure the onset of a decrease in intracellular ATP levels started after prolonged incubation, and with the highest concentration of clarithromycin an induction of coccoid forms was seen after 68 h. Metronidazole exposure resulted in the strongest initial decrease in intracellular ATP levels, and coccoid forms were seen after 21 h of exposure to high concentrations of metronidazole. Amoxicillin caused a low-level increase in resistant subpopulations, which indicates a need for surveillance of the amoxicillin susceptibility of H. pylori in order to detect decreasing susceptibility. No increase in the numbers of resistant subpopulations was demonstrated during clarithromycin exposure. Metronidazole selected resistant subpopulations, which caused high-level resistance in H. pylori.     

Efficacy and Pharmacological Mechanism of Pronase-Enhanced Low-Dose Antibiotics for Helicobacter pylori Eradication

This study examined the efficacy and pharmacological mechanism of pronase-assisted low-dose antibiotics for eradication of Helicobacter pylori. Mongolian gerbils infected with H. pylori received 7-day treatment (omeprazole, different concentrations of pronase, amoxicillin, and clarithromycin), and the efficacy was assessed using the eradication rate and the colonization of H. pylori. In Mongolian gerbils orally administered pronase, the thickness of the gastric mucous layer (GML) was examined using immunohistochemical and alcian blue staining, and the concentrations of amoxicillin in gastric tissue and serum were detected using high-performance liquid chromatography (HPLC). The eradication rates were 80.0% (12/15) in the high-pronase quadruple group (HPQG) and 86.7% (13/15) in the high-antibiotic group (HAG) (P = 1.000). The antibiotic dose in the HPQG was only 1/20 that in the HAG. Thirty minutes after oral treatment with pronase, the sticky protein of the GML was hydrolyzed, and the GML became thinner. Higher amoxicillin concentrations in both the gastric tissue and serum were observed in the pronase group than in the Am10 group. The concentration of amoxicillin in the Am10-plus-Pr108 group in gastric tissue was 3.8 times higher than in the Am10 group in 5 min. Together, these data suggest that pronase significantly reduced the dose of antibiotics used in H. pylori eradication. The pharmacological mechanism is likely pronase removal of the mucus layer, promoting chemical factor (i.e., gastric acid and pepsinogen) distribution and increasing the antibiotic concentrations in the deep GML, which acted on H. pylori collectively. Thus, pronase may enhance the level of antibiotics for eradication of H. pylori in the clinic.     

序贯疗法和三联疗法治疗幽门螺杆菌阳性溃疡的疗效观察

目的观察由奥关拉唑联合阿莫西林、克拉霉素、替硝唑组成的10日序贯疗法根除幽门螺杆菌（Hp）的疗效。方法210例Hp阳性的消化性溃疡患者,随机分为两组。治疗组采用前5d应用奥美拉唑20mg加阿莫西林1000mg,2次／d,后5d用奥美拉唑20mg加克拉霉素500mg加替硝唑500mg,2次／d,对照组采用10d奥美拉唑20mg加阿莫西林1000mg加克拉霉素500mg,2次／d。4周后复查Hp。结果治疗组Hp根除率92．4％,对照组78．1％,差异有统计学意义（P〈0．05）。结论以奥美拉唑、阿莫西林、克拉霉素、替硝唑组成的10日序贯疗法治疗成人Hp感染具有疗效高、耐受性和依从性好等优点。