A simple method for determining metronidazole resistance of Helicobacter pylori.

The reliability of methods for determination of Helicobacter pylori resistance to metronidazole has been found to depend upon the incubation time. Because the disk diffusion method is more vulnerable than other methods to prolonged incubation, this method has not been recommended for H. pylori. However, because media designed for rapid growth of H. pylori have been introduced, the time has come to look at the clinical usefulness of this inexpensive and simple method again. The correlation of readings obtained with the E test (AB Biodisk, Solna, Sweden) and Rosco's (Taastrup, Denmark) disk diffusion method for in vitro metronidazole resistance determination for H. pylori with a short incubation time (24 to 31 h) was studied. Plates which could not be read after 24 to 31 h were reincubated for another night. Fifty-seven consecutive clinical strains were tested. Because the rate of regrowth of H. pylori depends upon the age of the colonies inoculated, the reproducibility of resistance test results for young colonies versus old colonies was also studied. Resistance plates could be read after 24 to 31 h of incubation for 28 of 29 strains when the inoculum consisted of young colonies (3 to 4 days old). For these 29 strains, a high correlation (r = -0.937) was found between results obtained with the E test and those obtained with the disk diffusion test. A poorer correlation was found for old colonies (> or = 5 days old) (r = -0.742), which required a prolonged incubation for 8 of 23 strains. In conclusion, short incubation was successfully applied with young colonies. Results obtained with the simple and inexpensive disk diffusion method correlated well with those obtained with the E test.     

幽门螺杆菌耐甲硝唑基因分型与序列分析

目的 探讨幽门螺杆菌（Helicobacter pylori,Hp)rdxA基因型及其与甲硝唑耐药性的关系及耐药的分子机制。方法 对54例包括胃炎、消化性溃疡、胃癌患者的Hp分离株进行甲硝唑敏感实验，得到敏感株和耐药株；提取Hp基因组DNA，PCR扩增rdxA基因，并进行限制性片段长度多态性（RFLP）分型；统计学分析基因型和耐药性关系；对1株敏感株和2株耐药株rdxA基因测序分析突变情况。结果 rdxA基因可分为两型：Ⅰ型和Ⅱ型。Ⅰ型中的敏感株和耐药株所占比例为56%和44%，Ⅱ型中的敏感株占16％，耐药株占84％。经统计学分析，rdxA基因Ⅱ型与耐药性有相关性。rdxA基因测序分析显示耐药株存在编码区碱基置换及插入造成的移码突变；非编码区亦存在单个碱基缺失及置换突变。结论 rdxA基因Ⅱ型与Hp的甲硝唑耐药性密切相关，耐甲硝唑株主要表现为Ⅱ型。rdxA基因突变是耐甲硝唑的主要原因。     

High levels of resistance to metronidazole and clarithromycin in Helicobacter pylori strains in children

The aim of the study was to evaluate the prevalence of resistance to amoxicillin, metronidazole, and clarithromycin before treatment of Helicobacter pylori infection in children and to assess the evolution of resistance with time. The study was carried out between 1994 and 1999 with 150 H. pylori-positive children through gastric culture (antimicrobial susceptibility) and histology. All cultured H. pylori strains were sensitive to amoxicillin, 64 (43%) were resistant to metronidazole, 32 (21%) were resistant to clarithromycin, and 14 (9%) were resistant to both metronidazole and clarithromycin. The overall prevalence of resistance to metronidazole and clarithromycin did not change significantly with time. The study highlights the generalized high-level and stable metronidazole and clarithromycin resistance of H. pylori strains from children.     

Ribotyping patterns and emergence of metronidazole resistance in paired clinical samples of Helicobacter pylori.

Metronidazole-susceptible pretreatment isolates and metronidazole-resistant posttreatment isolates of Helicobacter pylori from 11 patients before and after unsuccessful triple therapy consisting of metronidazole, amoxicillin, and colloidal bismuth subcitrate were studied. Ribotyping (rRNA gene restriction pattern analysis) of the isolates demonstrated that all patients except one had identical digest patterns for pre- and posttreatment isolates.     

Characterization of the genes rdxA and frxA involved in metronidazole resistance in Helicobacter pylori

Metronidazole (Mtz) resistance in Helicobacter pylori has been found to be associated with mutations in rdxA, a gene encoding an oxygen-insensitive NADPH nitroreductase, and enhanced by mutations in frxA, a gene encoding a NAD(P)H-flavin oxidoreductase. The roles of these two genes in Mtz resistance in H. pylori were examined in this study. The rdxA and frxA genes were sequenced in nine pairs of strains isolated from biopsies obtained from patients before and after failed eradication treatments which included Mtz and resulted in the appearance of resistant strains. Metronidazole resistance could be explained in seven of these pairs of strains by mutations in rdxA and frxA. However, in one pair of strains, rdxA was identical in the susceptible and resistant strains, and only changes in frxA were observed; and in another pair, neither rdxA nor frxA were different in the susceptible and resistant strains. Sequencing of the upstream region of frxA and of the recA gene in the latter pair of strains did not reveal any mutations. To establish whether mutations in frxA alone could be involved in Mtz resistance, a resistant Escherichia coli strain transformed with the frxA of a Mtz susceptible H. pylori strain was rendered susceptible, and transformation with a mutated H. pylori frxA gene under the same conditions did not change the resistant E. coli phenotype. The results suggested that a Mtz resistance phenotype may arise in H. pylori without mutations in rdxA or frxA, or with mutations only in frxA.     

Morphological transformation of Helicobacter pylori during prolonged incubation: association with decreased acid resistance.

The survival of clinical isolates of H pylori at two cultural ages (two and four days) at pH 2, in the presence of different buffers, with and without urea, was investigated. It was found that the morphological changes which occur with longer incubation of H pylori have an inverse correlation with its resistance to an acidic environment. The finding that the addition of urea almost reversed this phenomenon and prolonged survival of the cultures emphasises the role of urea in the survival of H pylori in acidic environments.     

Universal high-level primary metronidazole resistance in Helicobacter pylori isolated from children in Egypt

Antimicrobial susceptibility testing was performed on 48 isolates of Helicobacter pylori recovered from Egyptian children undergoing routine endoscopies. The isolates were universally highly resistant to metronidazole, but resistance to other tested antimicrobial agents was rare (4% for clarithromycin, erythromycin, and azithromycin resistance versus 2% for ciprofloxacin and ampicillin resistance). Use of metronidazole for the treatment of H. pylori in Egypt should be avoided.     

Comparison of isolates of Helicobacter pylori and Helicobacter mustelae.

On the basis of analysis of protein profiles, isolates of Helicobacter pylori and Helicobacter mustelae were less than 40% similar. Cytotoxin produced by H. pylori was not detected in isolates of H. mustelae. Both bacterial species agglutinated human erythrocytes. These results substantiate a taxonomic difference between H. pylori and H. mustelae.     

Prevalence of primaryHelicobacter pylori resistance to metronidazole and clarithromycin in The Netherlands

The minimum inhibitory concentrations of metronidazole and clarithromycin were determined for 780Helicobacter pylori strains collected in 1994 and 1995 from three different regions in The Netherlands. The overall prevalence of primary metronidazole resistance was 17%, with resistance found more frequently in women (24%) than in men (13%). There was no significant difference between the levels of resistance in the three regions. Primary clarithromycin resistance was rare (1%) and relatively infrequent as compared to that found in other countries. Four of the six strains resistant to clarithromycin were also resistant to metronidazole.     

Comparison of Helicobacter pylori and attaching-effacing Escherichia coli adhesion to eukaryotic cells.

Adhesion of Helicobacter pylori was reported previously to be morphologically identical to "attaching and effacing" Escherichia coli. Therefore, the aim of the present study was to define the adhesion phenotype of H. pylori LC-11 to HEp-2, KATO-III, HEL, and CHO tissue culture cells. By using both staining of F-actin with fluorescein-labeled phalloidin and ultrastructural analysis, diffuse bacterial adhesion to discrete microvillus-denuded regions of the plasma membrane was observed in each of the infected cell lines. However, strain LC-11 did not induce formation of F-actin adhesion pedestals on the eukaryotic cells. H. pylori was negative by colony blot hybridization with an E. coli attaching and effacing gene probe. Elevations in inositol triphosphates followed infection of HEp-2 cells with H. pylori (405% of control values +/- 147%; P < 0.05). To correlate the observed histopathology with expression of the H. pylori phosphatidylethanolamine receptor, a thin-layer chromatography overlay-binding assay was used to identify receptors in each of the cell lines. H. pylori adhered to eukaryotic cells regardless of the presence (HEp-2, KATO-III, and CHO cells) or absence (HEL cells) of the lipid receptor as detected under the assay conditions. However, in comparison to cell lines that possess the phosphatidylethanolamine receptor, HEL cells demonstrated less quantitative H. pylori binding. These findings suggest that mechanisms distinct from E. coli enteropathogens underlie the adhesion of H. pylori to mucosal surfaces. In addition to the phosphatidylethanolamine H. pylori receptor, another host factor(s) likely mediates the attachment of H. pylori to human eukaryotic cells.     

Cytopathic effects of Helicobacter pylori on cultured mammalian cells.

Cytopathic effects of broth-culture filtrates from eight clinical isolates and one reference strain of Helicobacter pylori on three cultured mammalian cell lines were investigated. All the strains, including NCTC 11637, produced cytotoxic factors that caused intracellular vacuolation on these cell lines. AGS and SflEp cells were more sensitive than HEp-2 cells. To examine the role of urease in the cytotoxic effect, a urease-negative mutant was produced. Filtrates from both wild-type and mutant strains produced similar vacuolation on SflEp cells in the absence of urea, suggesting that H. pylori produces a cytotoxic substance other than urease. In contrast, ammonia alone, or jack bean urease with urea, also induced rounding and detachment of SflEp cells, whereas ammonium salts induced the production of small vacuoles. The combination of the broth filtrate of the wild-type strain and urea induced vacuolation followed by rounding and detachment of SflEp cells. Evidence is presented that the latter changes are due to ammonia produced during incubation. Nevertheless, the amounts produced were less than that needed to induce cytopathic effects by itself. These results suggest that the cytotoxic substance induces intracellular vacuolation, and that the vacuolated cells are more susceptible to killing by ammonia. Thus both the cytotoxic substance and urease may contribute to the lethal cytotoxicity of H. pylori in vitro.     

Attention to metabolic hunger and its effects on Helicobacter pylori infection

A significant decrease in the bacterial count of small intestinal mucosa has been observed in children with recurrent diarrhea or abdominal pain in the time that has elapsed from the previous meal. Humans may be trained to recognize metabolic feelings of hunger that are associated with a steady and slightly lower glycemia than baseline, between 4.7 and 3.9 mmol/L (intervention). An eating habit associated with a decrease in preprandial glycemia prevented diarrhea relapses, and was expected to impair intestinal microflora growth, including Helicobacter pylori in the stomach. The development of Helicobacter pylori infection might be prevented during childhood, and recovery from infection may be expected with intervention. The improvement in attention to metabolic feelings consisted of acquiring a predictive ability of glycemia by distinction between unsolicited hunger feelings (metabolic hunger) and those associated with external cues. Matching intake to the inbetween energy needs served to predict the subsequent emergence of the metabolic hunger. The matching was further compensated for the early or late emergence of metabolic hunger at the subsequent meals. Fruit and vegetables were increased to avoid abrupt glycemia lowering. This intervention was trained in 5-month periods. Subjects (209, 44, and 58) completed their training during 4-year periods between 1982 and 1994, and were enrolled in a prospective, controlled, randomized, interventional, preventive, and cohort study. The "prevention" hypothesis was tested in a subgroup of 86 healthy infants who were recalled in the years 1996 to 1998. A "recovery" study of approximately a 1-year intervention was investigated in 47 healthy subjects between ages 5 and 25, who were positive for anti-H. pylori and had no need for an immediate antibiotic treatment at entry. The following behavioral factors were recorded in a 7-day home diary and calculated: the fraction of meals induced by metabolic hunger out of 21 main mealtimes; average preprandial glycemia (DAP glycemia); daily intakes, activity; and bedtime hours. The decrease in preprandial glycemia was the objective measure of compliance with the recognition of "metabolic" hunger. Anthropometric measures and blood tests were obtained for nutritional and functional verifications. Average preprandial glycemia was 8.5 and 8.6% lower in the intervention groups than the control groups in the "prevention" and "recovery" studies, respectively, at the end of follow-up (p<0.05 and <0.001, respectively). A 4.7% seroprevalence of H. pylori infection was observed in the intervention group, with 30.2% in the control group at a mean age of 10 years after approximately an 8-year follow-up in the "prevention" study (p<0.0005). The seroprevalence decreased to 9 of 24 (37.5%) under intervention as opposed to 20 of 23 controls (87%) in the recovery study (p<0.002). A significant positive correlation was found between DAP glycemia and the anti-H. pylori serum antibody concentration (r = 0.52; p = 0.0002). A decrease in the level of immune stimulation by H. pylori infection was observed due to the intervention, which may have a preventive and therapeutic role on the infection.     

幽门螺杆菌对克拉霉素耐药分子机制研究进展

幽门螺杆菌（Hpylori,Hp）是慢性胃炎,消化性溃疡的重要致病因素。研究表明,Hp的根治和清除有利于溃疡的治愈。而Hp耐药直接影响Hp的根治和清除,Hp耐大环内酯类药物（克拉霉素）的机制与其23SrRNA的V区上的点突变有关。随着Hp耐药率的逐年升高,有关Hp的耐药分子机制和检测技术成为研究热点。因此,开展Hp耐药的相关研究对Hp的诊断和治疗有重大意义。     

Heterogeneity in susceptibility to metronidazole among Helicobacter pylori isolates from patients with gastritis or peptic ulcer disease.

Combination therapies that include metronidazole (MTZ) are the most successful therapies used in eradicating Helicobacter pylori. In this study, the prevalence and the relevance of heterogeneity in susceptibility to MTZ among H. pylori populations of 156 patients were evaluated. The results of this study show that 37 patients (24%) were infected with MTZ-resistant H. pylori (MIC > or = 8 micrograms/ml). Furthermore, 33% (52 of 156) of the patients were found to be infected with H. pylori populations heterogeneous for their susceptibility to MTZ. The reassessment of the MICs of MTZ for these 52 H. pylori populations revealed MTZ resistance in 28 of them, increasing the number of MTZ-resistant H. pylori populations among the 156 patients to 65 (42%). Out of 20 isolates, 2 (10%) heterogeneous in their susceptibility to MTZ also appeared to be heterogeneous at the genome level as determined by randomly amplified polymorphic DNA fingerprinting. In conclusion, the results show the limitations and risk of possible misinterpretations when only a single colony, picked from the primary H. pylori populations isolated from patients, is analyzed for its susceptibility to MTZ.     

Comparison of commercial diagnostic tests for Helicobacter pylori antibodies.

A number of serological tests measuring the presence of Helicobacter pylori-specific serum immunoglobulin G (IgG) are now commercially available. The aim of this study was to evaluate the clinical accuracy of five commercial H. pylori antibody tests: GAP-IgG (Biomerica), HELpTEST (AMRAD, Kew, Victoria, Australia), HELICO-G (Porton Cambridge), Pyloriset (Orion Diagnostica), and ROCHE (Roche Diagnostics). A total of 162 subjects presenting for routine upper endoscopy were studied. H. pylori was diagnosed if culture, histology, or both were positive. Ten milliliters of venous blood was collected at the time of endoscopy for serological assessment. The sensitivity and specificity of each test (GAP-IgG, HELpTEST, HELICO-G, Pyloriset, and ROCHE) were as follows: 83 and 79%, 92 and 77%, 86 and 65%, 89 and 56%, and 98 and 69%, respectively. Positive and negative predictive values were 97 and 83%, 90 and 91%, 76 and 83%, 68 and 84%, and 86 and 97%, respectively. The specificity of most tests increased by approximately 10% when sera from subjects less than 45 years old were examined. The number of sera falling into the grey zone for each test (an indeterminate result with respect to H. pylori status) varied between 2.5 and 19%. This study highlights the need for all serological kits to be independently evaluated on the population to be studied by testing against a microbiologically defined panel of H. pylori-positive and -negative sera.     

Antimicrobial resistance of Helicobacter pylori in Germany, 2015 to 2018

ObjectivesNational and international guidelines recommend empiric first-line treatments of individuals infected with Helicobacter pylori without prior antimicrobial susceptibility testing. For this reason, knowledge of primary resistance to first-line antibiotics such as clarithromycin is essential. We assessed the primary resistance of H. pylori in Germany to key antibiotics by molecular genetic methods and evaluated risk factors for the development of resistance.MethodsGastric tissue samples of 1851 yet treatment-naïve H. pylori-positive patients were examined with real-time PCR or PCR and Sanger sequencing for mutations conferring resistance to clarithromycin, levofloxacin and tetracycline. Clinical and epidemiological data were documented and univariable and multivariable logistic regression analyses were conducted.ResultsOverall primary resistances were 11.3% (210/1851) to clarithromycin, and 13.4% (201/1497) to levofloxacin; resistance to tetracycline (2.5%, 38/1497) was as low as combined resistance to clarithromycin/levofloxacin (2.6%, 39/1497). Female sex and prior antimicrobial therapies owing to unrelated bacterial infections were risk factors for clarithromycin resistance (adjusted OR (aOR) 2.3, 95% CI 1.6–3.4; and 2.6, 95% CI 1.5–4.5, respectively); older age was associated with levofloxacin resistance (aOR for those ≥65 years compared with those 18–35 years: 6.6, 95% CI 3.1–14.2).ConclusionsClarithromycin might still be recommended in first-line eradication therapies in yet untreated patients, but as nearly every tenth patient may carry clarithromycin-resistant H. pylori it may be advisable to rule out resistance ahead of treatment by carrying out susceptibility testing or prescribing an alternative therapy.