Primary resistance to clarithromycin in clinical strains of Helicobacter pylori isolated from children in Poland.

Helicobacter pylori resistance to clarithromycin is an important factor in the failure of eradication therapy. The resistance results from point mutations in the 23S rRNA gene of H. pylori. The prevalence of primary resistance of H. pylori to clarithromycin in children and mutations associated with resistance were studied and it was found that 23.5% (23/98) of H. pylori strains isolated in our hospital during 1998-2000 were resistant to clarithromycin. The primary resistance was mainly caused by an A2143G mutation, but the isolates with an A2142G mutation had higher MICs for clarithromycin compared with those with an A2143G mutation: median MIC 256 versus 16 mg/l. Comparison of our data with previous results showed that the prevalence of H. pylori resistance to clarithromycin in children has increased in Poland over the last three years, however the difference was not significant (23.5 vs. 17%, P=0.22).     

幽门螺杆菌的耐药分析及对Hp根除的影响

目的探讨幽门螺杆菌(Hp)对常用抗菌药的耐药性及对Hp根除的影响,给临床提供合理用药的科学依据.方法采用用改良布氏活性炭培养基(平板)在微需氧环境中培养幽门螺杆菌,并利用琼脂稀释法行幽门螺杆菌的药敏试验.并用三联疗法对62例消化性溃疡进行Hp根除治疗.结果从112例消化性溃疡患者胃黏膜中培养出Hp 62株,对阿莫西林、四环素、克拉霉素、甲硝唑、替硝唑、呋喃唑酮的耐药率分别为1.61%、3.23%、11.2%、58.1%、3.23%、0%.7d根除治疗对Hp的总根除率为:对甲硝唑及克拉霉素敏感株根除率为91.5%,对甲硝唑耐药株根除率为52%,对克拉霉素耐药株根除率为0(P＞0.05).结论阿莫西林、替硝唑、四环素、呋喃唑酮的耐药率较低;而甲硝唑和克拉霉素耐药率较高.其耐药影响Hp根除.     

Primary clarithromycin resistance in Italy assessed on Helicobacter pylori DNA sequences by TaqMan real-time polymerase chain reaction

BACKGROUND: Helicobacter pylori clarithromycin resistance is increasing worldwide and different mutations are involved in its mechanisms. Recently, molecular methods have been proposed to assess these mutations. AIM: To assess prevalence of primary clarithromycin resistance in two Italian areas, and the distribution of involved mutations, by using a novel method for real-time polymerase chain reaction. METHODS: Two hundred and thirty-two H. pylori-positive patients undergoing oesophagogastroduodenoscopy in two Italian towns (Rome, centre Italy; Foggia, south Italy) were enrolled. Helicobacter pylori infection was detected by histology, rapid urease and urea breath tests. Clarithromycin resistance was assessed by TaqMan real-time polymerase chain reaction on paraffin-embedded antral biopsies. Results Primary clarithromycin resistance was detected in 62 (26.7%) patients. Its prevalence did not differ between the two areas (31.5%, centre vs. 23.3%, south; P=0.17) and between non-ulcer dyspepsia and peptic ulcer patients (28.4% vs. 20.7%, P=0.2). The A2143G point mutation was detected in 35 (56.4%) patients, A2142G in 14 (22.6%), A2142C in eight (12.9%), whilst a double mutation (A2143G plus A2142C or A2142G) was present in the remaining five (8.1%) cases. CONCLUSIONS: Our study found that primary clarithromycin resistance is highly prevalent in both central and southern Italy, and that A2143G is the most frequent point mutation involved in these areas.     

Primary Helicobacter pylori resistance to metronidazole and clarithromycin in the Finnish population

AIM: To systematically determine Helicobacter pylori primary antimicrobial resistance in Finland and the associated demographic and clinical features. METHODS: A total of 342 adult patients referred for gastroscopy at 23 centres in different parts of Finland and positive for the rapid biopsy urease test were recruited. Clinical and demographic data were collected via a structured questionnaire. Patients with positive H. pylori culture and successful antibiotic sensitivity determination by the E-test method (n = 292) were included in the present analysis. RESULTS: The study population consisted of 134 men and 158 women, mean age 56 years (95% CI, 55-58 years). Resistance to metronidazole was 38% (110 of 292) and to clarithromycin 2% (seven of 292). Resistance to metronidazole was higher in women than in men (48% vs. 25%, P < 0.001). Previous use of antibiotics for gynaecological infections predicted metronidazole resistance (P = 0.01), and previous use of antibiotics for respiratory (P = 0.02) and dental infections (P = 0.02) the clarithromycin resistance. We observed no major geographical variations in metronidazole resistance. CONCLUSIONS: The primary metronidazole resistance of H. pylori was 38% and was common in women previously treated for gynaecological infections. Primary clarithromycin resistance was uncommon (2%) and may associate with previous dental and respiratory infections.     

Metronidazole resistance in Helicobacter pylori

Modern triple drug regimens are highly effective for treating Helicobacter pylori infection, but bacterial resistance to one of the most effective antibiotics, metronidazole, is a serious and increasing problem. The activity of metronidazole in H. pylori is dependent on reduction of its nitro moiety to highly reactive compounds that cause DNA strand breakage. The acquisition of resistance is highly associated with mutational inactivation of the rdxA gene, which encodes an oxygen-insensitive NADPH nitroreductase. Recent evidence has suggested that inactivation of frxA (NADPH flavin oxidoreductase), fdxB (ferredoxin-like protein) and possibly other reductase-encoding genes may also contribute to the resistant phenotype. Improved understanding of the mechanisms of metronidazole resistance in H. pylori is essential for the development and validation of biopsy-based tests for detection of resistance in clinical practice.     

Role of NADPH-insensitive nitroreductase gene to metronidazole resistance of Helicobacter pylori strains

Background and the purpose of the study

Current anti-H. pylori therapies are based on the use of two antibiotics with a proton pump inhibitor and/or a bismuth component. Metronidazole is a key component of such combination therapies in Iran. The aim of this study was to determine the role of rdxA gene in resistant strains of H. pylori isolated from Shahrekord Hajar hospital to metronidazole.

Methods

This study was a cross-sectional method, which was carried out on 263 patients who referred to endoscopy department of Hajar hospital, in 2007. Biopsy samples were cultured on selective Brucella agar containing 10% blood and incubated under microerophilic condition at 370C for 3–7 days. Suspected colonies were tested by Gram staining, urease, oxidase and catalase activities. Organisms were confirmed to be H. pylori on the basis of the presence of ureC(glmM) gene by PCR.Specific primers were used for detection of rdxA gene mutation.

Results

Eighty and four strains of H. pylori determined by PCR method. Of the isolated strains, 49 (58.33%) were resistant, 7 (8.33%) were semi-sensitive to metronidazole and 200bp deletion in rdxA gene was observed in 2 strains.

Conclusion

Because of the high metronidazole resistance in patients under study it was necessary to replace it by other antibiotics in therapeutic regimens. On the basis of low frequency of resistance mutation in rdxA gene, sequence analysis for identification of other mechanisms is suggested.     

Factors affecting the variation in antibiotic resistance of Helicobacter pylori over a 3-year period

Strains of Helicobacter pylori, isolated from 300 patients between 1996 and 2000 were tested for their sensitivity to clarithromycin, metronidazole and amoxycillin. Primary resistances (95% CI) were 9. 7% for clarithromycin and 21.7% for metronidazole. No strains were resistant to amoxycillin. There was no significant difference between the number of resistant strains in the male and female groups. Clarithromycin resistance was more common in older patients (P<0.01) and metronidazole resistance was more common in patients with peptic ulcer compared with patients with chronic gastritis (P<0. 05). Logistic regression analysis confirmed these results.     

231例血液感染人苍白杆菌临床分布及耐药性分析

目的调查血液感染人苍白杆菌的临床分布及耐药性,为抗菌药物的使用及感染的控制提供流行病学资料。方法回顾性分析广东省深圳市中医院及四川省内江市第一人民医院2011年1月²013年12月住院及门诊就诊患者血液培养分离的人苍白杆菌的临床分布及对12种抗菌药物的耐药情况。结果分离出人苍白杆菌231株,主要集中在感染科、重症监护科、肿瘤科等;对哌拉西林、氨曲南、头孢唑啉、氨苄西林-舒巴坦、哌拉西林-他唑巴坦、头孢噻肟耐药率高,耐药率>90%;对头孢吡肟、厄他培南、亚胺培南、庆大霉素、环丙沙星、美罗培南敏感性较好,耐药率<10%。随时间的推移,其耐药率有逐年增高趋势。结论人苍白杆菌已成为血液感染的重要病原菌之一;持续、准确地监测其流行趋势及耐药情况对该菌感染的防治具有重要意义。     

Helicobacter pylori: cultivability and antibiotic susceptibility of coccoid forms

Helicobacter pylori is an actively dividing helical bacterium that changes to coccoid morphology as the culture ages. It has been suggested that the coccoid forms may be involved in transmission of infection and in relapses following antimicrobial therapy. The aim of this investigation was to determine the survival and susceptibility of the coccoid forms to amoxycillin, erythromycin, gentamicin and metronidazole. Colony counts and microscopic examination were performed after 1–4 weeks of culture. At 2 and 4 weeks, identical cultures were treated with the antibiotics for 24 h. Our results showed that 4-week cultures of coccoid forms were cultivable after antibiotic treatment.     

产超广谱β-内酰胺酶大肠埃希菌和肺炎克雷伯菌的耐药性研究

目的：了解我院临床分离产超广谱β-内酰胺酶（ESBLs）大肠埃希菌和肺炎克雷伯菌的检出率及耐药性情况，为指导临床用药提供依据。方法：对我院1999—2005年分离的854株大肠埃希菌、300株克雷伯菌用标准纸片扩散确证法检测其ESBLs产生率；采用K-B法进行药敏检测。结果：1999年我院产ESBLs大肠埃希菌和肺炎克雷伯菌的检出率分别为26．4％和21．9％，2005年的两者检出率分别增长为48．6％和47．7oA。除亚胺培南的耐药率为0％、产ESBLs大肠埃希菌和肺炎克雷伯菌对阿米卡星、呋喃妥因的耐药率分别为17．9％和6．2％外，2005年我院产ESBLs菌株对其他抗菌药物耐药率均达74．4％以上，且产ESBLs菌株的耐药率远高于非产ESBLs菌株。结论：医院应重视对产ESBLs菌株的检测，合理选用抗菌药物治疗感染。对于产ESBLs大肠埃希菌和肺炎克雷伯菌感染的治疗，亚胺培南应作为首选药物。     

Strategies to treat patients with antibiotic resistant Helicobacter pylori

Increased resistance to clarithomycin and metronidazole, the two main antibiotics used to treat Helicobacter pylori infection, has led to a search for alternatives to the proton pump inhibitor based triple therapies commonly used. The main rescuse therapy is a bismuth-based quadruple therapy. However, triple therapies with tetracycline and metronidazole or amoxicillin and metronidazole can be considered in the case of clarithomycin resistance. They can also be used in the case of metronidazole resistance by increasing the dose and duration of metronidazole. The only therapy without clarithomycin and metronidazole includes rifabutin and amoxicillin. Dual therapies with amoxicillin and a proton pump inhibitor at high dose can also be used.     

Successful Helicobacter pylori eradication incorporating a one-week antibiotic regimen

Background: The optimum regimen for the eradication of Helicobacter pylori remains unclear. The aim of this study was to determine the efficacy and tolerability of omeprazole 40 mg daily given for 2 weeks, plus amoxycillin 500 mg t.d.s. and metronidazole 400 mg t.d.s. given for the first 7 days, in the treatment of H. pylori associated peptic ulcer disease. Results: One hundred and thirty-two consecutive patients with peptic ulcer disease were entered into the study (89 male, 41 female; median age 47 years; inter-quartile range: 36–58 years). H. pylori was eradicated successfully in 109 of 130 patients (intention-to-treat: 83%; 95% confidence limits: 76–89%); per protocol: 85% (95% CI: 78–91%)). Ninety per cent of patients completed the full course of therapy. Only four patients (3%) stopped treatment as a result of side effects although these occurred in 41% of patients. One patient developed pseudomembranous colitis requiring hospital admission. Conclusion: Omeprazole combined with one week of treatment of amoxycillin and metronidazole is an effective and well tolerated Helicobacter eradication regimen. Occasional severe side effects remain a risk, even when the duration of antibiotic exposure is reduced.     

Primary and secondary clarithromycin, metronidazole, amoxicillin and levofloxacin resistance to Helicobacter pylori in southern Poland

The aim of this study was to assess the primary and secondary resistance of H. pylori strains cultured from adult patients of the Ma?opolska region of Poland, mainly of Kraków and the surrounding areas, to antibacterial agents (amoxicillin, clarithromycin, metronidazole and levofloxacin). In total, 115 H. pylori strains were isolated, of which 90 strains originated from patients who had never been treated for H. pylori infection, while the remaining 25 were isolated from patients in whom eradication of the infection failed after treatment. All tested H. pylori strains were susceptible to amoxicillin. Forty-four percent of strains isolated were resistant to metronidazole. The primary and secondary resistance to this antimicrobial chemotherapeutic reached 37% and 72% (p = 0.002), respectively. In total, 34% of strains were resistant to clarithromycin, and the ratio of strains with secondary resistance was significantly greater than that of the strains with primary resistance (80% vs. 21%, p < 0.001). The double resistance to both metronidazole and clarithromycin was confirmed in 23% of H. pylori strains. Five percent of H. pylori strains were resistant to levofloxacin, while primary and secondary resistance to this drug accounted for 2% and 16% (p = 0.006), respectively. In total, 4% of H. pylori strains were simultaneously resistant to metronidazole, clarithromycin and levofloxacin. Thus, the high resistance to metronidazole and clarithromycin excludes the possibility of using these drugs for treatment of H. pylori infection without earlier antibiogramming. Levofloxacin, as a drug of high efficacy against H. pylori, should be reserved for an “emergency” therapy and used in a limited capacity in order to preserve its potent antimicrobial activity. The Polish Society of Gastroenterology recommends levofloxacin as a third-line therapy [14].     

Review article: nitroimidazole resistance in Helicobacter pylori

The efficacy of a nitroimidazole-containing regimen for the treatment of Helicobacter pylori infection is decreased by nitroimidazole resistance. Nitroimidazoles are meta- bolized by H. pylori by several nitro-reductases of which an oxygen-insensitive NADPH nitroreductase encoded by the rdxA gene is the most important. Null mutations in this gene are associated with resistance.
Susceptibility testing to nitroimidazoles may give variable results. This is not only related to the slow growth under specific conditions, but also to variability in the activity of the other nitroreductases and the ability to deactivate toxic metabolites of an NI and to repair DNA damage. Moreover, co-infections with resistant and susceptible bacteria are frequently found. The presence of nitroimidazole resistance is related to the previous use of this drug. The prevalence of resistance is rising and nowadays 10–50% of the isolates are resistant.
Resistance reduces the efficacy of a treatment regimen to a variable degree. This is related to efficacy of the other components of the regimen and the treatment duration. Whether a nitroimidazole is still effective in resistant strains remains unresolved.
When nitroimidazole resistance is present, a nitro-imidazole-containing regimen should be avoided or a regimen with other highly effective components should be used.     

Antibiotic resistance problems with Helicobacter pylori.

Helicobacter pylori is very susceptible in vitro to most antibiotics, but when they are used in the clinical setting, eradication of the bacteria from the gastric mucosa is not obtained. Dual or triple therapy including two of the following antibiotics: amoxicillin, tetracycline, metronidazole or clarithromycin, plus a proton pump inhibitor, bismuth salt or ranitidine bismuth citrate is the most frequently used. Various in vitro susceptibility methods have been used: disk diffusion, agar dilution and Epsilometer test (E-test). Metronidazole resistance among H. pylori strains is now found worldwide, and resistance rates vary according to the population studied. It is higher in developing than in developed countries and it could reach 80-90% in Africa. The prevalence on clarithromycin resistance is much lower, usually below 10%, although very high values are reported in Peru. Infection with metronidazole- or clarithromycin-resistant H. pylori strains is correlated with treatment failure when using regimens including these antibiotics.     

Helicobacter pylori strains and histologically-related lesions affect the outcome of triple eradication therapy: a study from southern Italy

BACKGROUND: Certain evidence suggests that Helicobacter pylori strains expressing genes for cytotoxin production show a higher sensitivity than non-cytotoxic organisms to eradication treatment. No data are available on the involvement of bacterium-related lesions in different therapeutic outcomes. AIMS: (i) To investigate whether differences in eradication rates may be related to the different expression of virulent strains (cagA, vacA, iceA) in patients undergoing proton pump inhibitor-based triple therapy, and (ii) to evaluate whether therapeutic outcome may be affected by bacterium-induced gastric lesions. METHODS: One hundred and ten H. pylori-positive subjects were enrolled. H. pylori was genotyped by polymerase chain reaction. Treatment consisted of lansoprazole-amoxicillin-clarithromycin, twice daily for 1 week. Eradication was checked by urea breath test. RESULTS: The eradication rate was 70%, and the absence of cagA was associated with unsuccessful treatment. No difference between the groups with successful and unsuccessful eradication was found with regard to vacA and iceA. Lympho-epithelial lesions and fibrosis were associated with unsuccessful treatment. CONCLUSIONS: The present data confirm the importance of cagA (but not vacA and iceA) as a predictor of successful eradication. When fibrosis and lympho-epithelial lesions are present, therapy appears to be less effective. Therefore, these histological features may be involved in an unsuccessful therapeutic outcome.