Clarithromycin resistance of Helicobacter pylori strains isolated from children' gastric antrum and fundus as assessed by fluorescent in-situ hybridization and culture on four-sector agar plates

Helicobacter pylori heteroresistance to clarithromycin in adults-New data by in situ detection and improved concept

BACKGROUND

Clarithromycin (Cla) heteroresistance of Helicobacter pylori (H pylori) infections is commonly assessed by comparing the resistance status of antrum and corpus biopsy samples and by demonstrating the discrepancy between them (interniche heteroresistance). However, fluorescence in situ hybridization (FISH) technique is capable of showing the synchronous presence of susceptible and resistant bacteria (intraniche heteroresistance), enabling the detection of heteroresistant H pylori populations within one biopsy sample.

MATERIALS AND METHODS

Antrum and corpus biopsy specimens of 305 H pylori-infected patients were investigated with an rRNA-targeted Cla-resistance FISH test. Anamnestic data were collected from the institutional electronic register. Prevalence rates of susceptible, homo- and heteroresistant cases were correlated with the anamnestic and clinicopathological data.

RESULTS

Overall Cla-resistance rate was 23.9% (73 cases), consisting of 35 (11.5%) homoresistant and 38 (12.5%) heteroresistant cases. Thirty-five patients had at least one biopsy site where susceptible and resistant bacteria were present simultaneously. From this subset, 20 cases demonstrated intraniche heteroresistance on both sites. Prior Cla-based eradication attempts were more frequent in homoresistant than in susceptible and heteroresistant cases (P < .001, P < .001, respectively). Cla-containing therapy eradicated heteroresistant infections at a significantly lower rate in comparison with susceptible cases (P = .0112), but more effectively than homoresistants (P = .0393).

CONCLUSIONS

The most frequent type of Cla-heteroresistance is the coexistence of susceptible and resistant H pylori bacteria in the same location (intraniche heteroresistance). A previous Cla-based eradication attempt predisposes patients to homoresistant infection. Heteroresistance is characterized by a non-eradication-related background and intermediate characteristics in many respects when compared to susceptible and homoresistant cases.

Increasing metronidazole and rifampicin resistance of Helicobacter pylori isolates obtained from children and adolescents between 2002 and 2015 in southwest Germany

BACKGROUND

Increasing antibiotic resistance has been reported for Helicobacter pylori, but data on the prevalence of antibiotic resistance of H. pylori in pediatric patients and the development of resistance over time are sparse.

METHODS

Data for 610 H. pylori isolates obtained between 2002 and 2015 from gastric biopsies of 582 (mainly treatment-naïve) pediatric patients from southwest Germany were analyzed retrospectively regarding the antibiotic susceptibility determined by Etest and patients' characteristics.

RESULTS

Overall resistance to metronidazole, clarithromycin, and rifampicin was 28.7%, 23.2%, and 13.3%, respectively, while resistance to amoxicillin was rare (0.8%). Simultaneous resistance to metronidazole and clarithromycin was observed for 7.7% of the isolates, and 2.3% were resistant to metronidazole, clarithromycin, and rifampicin. Differences between primary vs secondary resistance existed for metronidazole (24.7% vs 38.8%, P=.01) and clarithromycin (17.2% vs 54.1%, P=.0001). From 2002-2008 to 2009-2015, resistance to metronidazole increased from 20.8% to 34.4% (P=.003) and to rifampicin from 3.9% to 18.8% (P=.0001); this was not associated with increased numbers of patients previously treated for H. pylori infection in the second study period. In contrast, resistance to clarithromycin did not change significantly over time. Resistance was not associated with age, sex, or family origin in Europe.

CONCLUSIONS

The considerable antibiotic resistance of H. pylori isolates argues for standard antibiotic susceptibility testing of H. pylori in pediatric patients prior to the initiation of antibiotic therapy.

Fluorescence in situ hybridization (FISH) in the microbiological diagnostic routine laboratory: a review

Early identification of microbial pathogens is essential for rational and conservative antibiotic use especially in the case of known regional resistance patterns. Here, we describe fluorescence in situ hybridization (FISH) as one of the rapid methods for easy identification of microbial pathogens, and its advantages and disadvantages for the diagnosis of pathogens in human infections in the laboratory diagnostic routine. Binding of short fluorescence-labeled DNA or nucleic acid-mimicking PNA probes to ribosomes of infectious agents with consecutive analysis by fluorescence microscopy allows identification of bacterial and eukaryotic pathogens at genus or species level. FISH analysis leads to immediate differentiation of infectious agents without delay due to the need for microbial culture. As a microscopic technique, FISH has the unique potential to provide information about spatial resolution, morphology and identification of key pathogens in mixed species samples. On-going automation and commercialization of the FISH procedure has led to significant shortening of the time-to-result and increased test reliability. FISH is a useful tool for the rapid initial identification of microbial pathogens, even from primary materials. Among the rapidly developing alternative techniques, FISH serves as a bridging technology between microscopy, microbial culture, biochemical identification and molecular diagnostic procedures.

Epidemiology, Diagnosis, and Risk Factors of Helicobacter pylori Infection in Children

H. pylori infection is a global public health problem associated with some gastrointestinal diseases in children, especially in developing countries, since prevalence of H. pylori is low in the developed world. Both noninvasive (stool antigen test, urea breath test, and blood test) and invasive (histology, rapid urease test, and microbiological culture) tests have been utilized to detect H. pylori infection. However, a single test is not reliable enough and does not provide accurate enough data to determine H. pylori infection among children. Risk factors of H. pylori infection in children were related to ethnicities, household properties, geographic location, living conditions, water sources, type of housing, presence/absence of sewage systems, and garbage collection within the living environment. These risk factors were usually associated with the socioeconomic status of the family. This review article aims to determine the gaps in the knowledge of the epidemiology, risk factors, and diagnostic tests of H. pylori infection among children. How to cite this article: Ozbey G, Hanafiah A. Epidemiology, Diagnosis, and Risk Factors of Helicobacter pylori Infection in Children. Euroasian J Hepato-Gastroenterol 2017;7(1):34-39.

In vitro antimicrobial susceptibility of Helicobacter pylori to nine antibiotics currently used in Central Italy

OBJECTIVE

Helicobacter pylori expresses an increased resistance in respect to antimicrobials currently used in therapy. The aim of this study was to evaluate the antimicrobial profiles of H. pylori isolates to nine conventional antibiotics used in a Central Region (Abruzzo) of Italy.

MATERIALS AND METHODS

Biopsies were taken from antrum and fundus of 112 adult and 3 children with Urea Breath Test positive with dyspeptic symptoms and analyzed for H. pylori culture and antibacterial activity. Antimicrobial susceptibility tests were performed for clarithromycin, metronidazole, levofloxacin, moxifloxacin, ciprofloxacin, tetracycline, amoxicillin, ampicillin, and rifabutin by a modified agar dilution susceptibility test.

RESULTS

Bacterial culture was successful in 100 out of 115 patients. Helicobacter pylori strains were isolated from 98 antrum and 83 fundus samples. The rate of recovery of H. pylori strains was 90.50% (181/200). The percentages of resistance were as follows: clarithromycin 72.44% antrum, 72.28% fundus; metronidazole 34.69% antrum, 42.16% fundus; levofloxacin 42.85% antrum, 53.01% fundus; moxifloxacin 37.35% antrum, 46.57% fundus; ciprofloxacin 39.47% antrum, 44.28% fundus; tetracycline 2.63% antrum, 2.85% fundus; amoxicillin 1.02% antrum, 1.20% fundus; ampicillin 0% antrum and fundus and rifabutin 0% antrum, 1.20% fundus. A total of 35 subjects harbored multi-resistant strains.

CONCLUSIONS

This study underlines the high rate of resistance to clarithromycin, metronidazole and quinolones, which may reflect an overuse of them. Culture and susceptibility test, should be performed to prevent the emergence of multi-resistance and to assess an efficacious regimen.

Emerging rapid resistance testing methods for clinical microbiology laboratories and their potential impact on patient management

Atypical and multidrug resistance, especially ESBL and carbapenemase expressing Enterobacteriaceae, is globally spreading. Therefore, it becomes increasingly difficult to achieve therapeutic success by calculated antibiotic therapy. Consequently, rapid antibiotic resistance testing is essential. Various molecular and mass spectrometry-based approaches have been introduced in diagnostic microbiology to speed up the providing of reliable resistance data. PCR- and sequencing-based approaches are the most expensive but the most frequently applied modes of testing, suitable for the detection of resistance genes even from primary material. Next generation sequencing, based either on assessment of allelic single nucleotide polymorphisms or on the detection of nonubiquitous resistance mechanisms might allow for sequence-based bacterial resistance testing comparable to viral resistance testing on the long term. Fluorescence in situ hybridization (FISH), based on specific binding of fluorescence-labeled oligonucleotide probes, provides a less expensive molecular bridging technique. It is particularly useful for detection of resistance mechanisms based on mutations in ribosomal RNA. Approaches based on MALDI-TOF-MS, alone or in combination with molecular techniques, like PCR/electrospray ionization MS or minisequencing provide the fastest resistance results from pure colonies or even primary samples with a growing number of protocols. This review details the various approaches of rapid resistance testing, their pros and cons, and their potential use for the diagnostic laboratory.

Comparison of sequential and standard therapy for Helicobacter pylori eradication in children and investigation of clarithromycin resistance

AIMS

The aim of the present study was to compare the efficacy of sequential and standard triple-drug regimen for Helicobacter pylori (H pylori) eradication in children and to determine the primary resistance rate to clarithromycin.

METHODS

Children with H pylori infection randomized to receive either standard regimen (n = 28) consisting of lansoprazole for 30 days, amoxicillin and clarithromycin for 14 days or sequential regimen (n = 16) consisting of lansoprazole for 30 days, amoxicillin for 7 days, followed by clarithromycin and metronidazole for the next 7 days. Clarithromycin susceptibility of H pylori was assessed with fluorescence in-situ hybridization technique. Eradication was controlled by C urea breath test or monoclonal stool antigen test 4 weeks after the end of the therapy.

RESULTS

H pylori eradication rate was higher in the sequential therapy group (93.7%), compared with the standard therapy group (46.4%) (P = 0.002). There was no difference in adverse drug reactions and in compliance to the treatment between the groups. Primary clarithromycin resistance rate for H pylori was found as 25.7% (n = 9). All of the patients having clarithromycin resistance were coincidentally in the standard therapy group. After the exclusion of these 9 patients, sequential therapy was again found to be more effective than the standard therapy (P = 0.02).

CONCLUSIONS

Sequential therapy seems highly effective for eradicating H pylori in children; however, the difference between 2 groups in resistant strains was the limitation of the study. Our country needs to reassess the effectiveness of standard triple therapy regimen for H pylori eradication.

Helicobacter pylori clarithromycin resistance detected by Etest and TaqMan real-time polymerase chain reaction: a comparative study

The aim of the work was to compare H. pylori clarithromycin-resistance according two methods. Etest was performed on H. pylori isolated from gastric biopsy samples. TaqMan Real-Time-PCR (RT-PCR) was performed on paraffin-embedded gastric biopsy samples of the same patients. Forty-seven out of 88 strains were resistant to clarithromycin by Etest, whereas RT-PCR detected this resistance on paraffin-embedded specimens of 50 patients. RT-PCR performed on paraffin-embedded biopsy specimens of 47 patients infected with H. pylori resistant to clarithromycin as detected by Etest, revealed the presence of a resistant strain only in 40 samples. RT-PCR performed on samples of 41 patients harbouring clarithromycin-susceptible H. pylori strains showed the presence of 31 susceptible and 10 resistant strains. RT-PCR detected 18 cases with heteroresistant status. The difference between the two tests in detecting clarithromycin-resistance was not statistically significant even if RT-PCR detected more resistant cases. The genotyping resistance on paraffin-embedded gastric biopsy specimens may be used to establish resistance to clarithromycin before the treatment when culture and susceptibility testing are not available. In case of failure of an empirical clarithromycin-based triple antimicrobial treatment, RT-PCR performed on paraffin-embedded biopsy sample will establish the primary resistance to clarithromycin. In addition, this test can be useful for epidemiological investigation as well as for monitoring the evolution of clarithromycin resistance along the time.

Monitoring of antibiotic resistance rates of Helicobacter pylori in Austrian children, 2002-2009

We retrospectively studied antibiotic resistance rates of H. pylori and their temporal changes in children. Resistance rates were 21.6% for both clarithromycin and metronidazole. There was no overall difference between children with or without migrational background. Resistance rates increased over time, and patients without migrational background showed a significant increase in metronidazole resistance. Our study emphasizes antibiotic resistance monitoring of H. pylori in children.

Sequential therapy versus tailored triple therapies for Helicobacter pylori infection in children

AIMS

The aim of the study was to compare sequential versus tailored triple therapy regimens on Helicobacter pylori (H pylori) eradication rates in children and to assess the effect of antimicrobial susceptibility.

PATIENTS AND METHODS

Prospective, open-label, multicenter study. Children received randomly either a 10-day sequential treatment comprising omeprazole (OME) with amoxicillin for 5 days and OME, clarithromycin (CLA), and metronidazole (MET) for the remaining 5 days, or a 7-day triple therapy comprising OME with amoxicillin and CLA in cases of a CLA-susceptible strain or MET in cases of CLA-resistant strain. H pylori eradication was assessed by C-urea breath test.

RESULTS

One hundred sixty-five children, 95 girls and 70 boys, of median age 10.4 years, were included. The intention-to-treat (ITT) eradication rate was 76.9% (sequential 68/83 = 81.9%, triple therapy 59/82 = 71.9%, ns), and the per-protocol (PP) eradication rate was 84.6% (sequential 68/77 = 88.3%, triple therapy 59/73 = 81.8%, ns). Eradication rates tended to be higher using the sequential treatment, but the difference was only statistically significant for ITT analysis in children harboring both CLA- and MET-susceptible strains (87.8% vs 68.5%, odds ratio [OR] 3.3, P = 0.03). Both ITT and PP eradication rates were significantly lower with sequential treatment in CLA-resistant compared with CLA-susceptible strains (ITT: 56.2% vs 72.7%, OR 5.5, P = 0.008; PP 64.3% vs 80.0%, OR 7.9, P = 0.009). Both treatments were well tolerated.

CONCLUSIONS

Sequential treatment is greatly effective for eradicating H pylori in children except in CLA-resistant strains. Sequential treatment can be used as a first-line therapy, but only in areas with a low CLA resistance rate.

Clarithromycin-resistant genotypes and eradication of Helicobacter pylori

OBJECTIVE

To compare the eradication rates among the different point mutations and the efficacy of triple therapy and a sequential regimen according to genotypic resistance.

STUDY DESIGN

Post hoc retrospective cohort study in a tertiary referral center for pediatric gastroenterology in southern Italy. All 168 children who were positive for Helicobacter pylori were enrolled. Patients had received clarithromycin-based 7-day triple therapy (73 children) or 10-day sequential therapy regimen (95 children). Real-time polymerase chain reaction for assessing clarithromycin resistance was performed on sections of paraffin-embedded gastric biopsy samples.

RESULTS

H pylori eradication was achieved in 16 of 32 (50%) children with the A2143G mutation, in 8 of 10 patients with either A2142G or A2142C strains (80%), and in 112 of 116 children with susceptible strains (88.9%). The presence of A2143G mutation was associated with a lower cure rate compared with the rate in the absence of this mutation (50% vs. 89%; P = .001). The sequential regimen achieved a higher cure rate than triple therapy in patients with A2143G mutant strains (80% vs nil; P < .001).

CONCLUSIONS

The A2143G mutation confers higher risk of treatment failure. Sequential regimen has higher efficacy than standard therapy, even in children with A2143G mutatant strains.

Phenotypic and genotypic Helicobacter pylori clarithromycin resistance and therapeutic outcome: benefits and limits

INTRODUCTION

Primary clarithromycin resistance is increasing worldwide, and it has been regarded as the main factor reducing the efficacy of Helicobacter pylori therapy. However, the clinical consequence of either phenotypic or genotypic resistance still remains unclear. This study aimed to evaluate: (i) the concordance between phenotypic (culture) and genotypic (real-time PCR) tests in assessing primary clarithromycin resistance; and (ii) the role of both in therapeutic outcome.

METHODS

A post hoc subgroup study was selected from a double-blind, placebo-controlled trial, enrolling 146 patients with dyspepsia or peptic ulcers never previously treated. Real-time PCR and Etest on bacterial culture for assessing clarithromycin resistance were performed. [(13)C]urea breath test (UBT), histology and rapid urease tests at entry and UBT after 4-8 weeks were used to assess infection and eradication. All patients received a 10 day therapy.

RESULTS

Prevalence of clarithromycin phenotypic resistance was significantly lower as compared with genotypic resistance (18.4% versus 37.6%, P < 0.001). A concordance between the two methods was present in 71.2% of cases. A significant difference in the eradication rate was seen between clarithromycin-susceptible and -resistant strains, when assessed with either Etest (92.4% versus 55.5%, P < 0.001) or a PCR-based method (94.5% versus 70.9%; P < 0.001). Of note, the eradication rate showed the lowest value (30.7%) when phenotypic bacterial resistance was genetically linked to the A2143G point mutation.

CONCLUSIONS

This study showed that: (i) there is a relevant discordance between the two methods; and (ii) phenotypic clarithromycin resistance markedly reduces H. pylori eradication when it is linked to a specific point mutation.

Helicobacter pylori diagnostic tests in children: review of the literature from 1999 to 2009

The array of tests that can be used for diagnosis of Helicobacter pylori infection is large, and it can be confusing to define which test to use particularly in children where results may not be comparable to those obtained in adult patients. Using PubMed, we reviewed the English literature from January 1999 to May 2009 to identify articles that determined sensitivity and specificity of H. pylori invasive and non-invasive diagnostic tests in children. We excluded articles that presented a review of the literature, abstracts, case reports, or series where children's results could not be separated from adult populations. Of the tissue based methods, rapid urease tests have better sensitivity than histology to detect presence of H. pylori; however, histology can detect the pathology associated with disease including gastritis, intestinal metaplasia, and other conditions that could be the cause of the child's symptoms. Culture of gastric tissues or stool has 100% specificity but sensitivity is low. Of the serologic tests, immunoblot has the best sensitivity. The urea breath tests have >75% sensitivity for detection of H. pylori before and after treatment. Immunoassays in stool using monoclonal antibodies have >95% sensitivity for detection of H. pylori before and after treatment. PCR testing can be performed in tissue and stool samples and can detect genes associated to antibiotic resistance. In summary, the current commercial non-invasive tests have adequate sensitivity and specificity for detecting the presence of H. pylori; however, endoscopy with histopathology is the only method that can detect H. pylori and lesions associated with the infection.

Diagnosis of Helicobacter pylori infection

The articles published this last year in the field of Helicobacter pylori diagnosis reported the development of in vivo histology, small improvements in some invasive methods (urease test, culture, and histology) and new kits for the stool antigen tests. They also contributed to increasing our knowledge, by further exploration into specific conditions for the urea breath test and into the significance of cagA antibodies. The role of serum markers of atrophy was also confirmed. Molecular methods are still being developed for direct genotyping, detection of H. pylori and its clarithromycin resistance, either by polymerase chain reaction or fluorescent in-situ hybridization. For the first time, there was a report on a possible interest of magnetic resonance spectroscopy.

Helicobacter pylori infection in pediatrics

his review summarizes the articles published on Helicobacter pylori infection in children between April 2008 and March 2009. Recent evidence highlights the decreasing prevalence trend of H. pylori infection and supports both intrafamilial and extrafamilial transmission. The association with various symptoms is still being debated. Interestingly, H. pylori infection seems inversely associated with allergic diseases. Monoclonal stool antigen tests are widely used and accurate for the diagnosis of H. pylori infection, but less accurate in young children. The new biprobe real-time PCR assay applied to stools showed a poor sensitivity in children. Using the urea hydrolysis rate next to the delta over baseline values, the (13)C-urea breath test provides excellent results for all age children, even for young children. Treatment of H. pylori infection remains a challenge, considering suboptimal efficacy of current therapy. Among emerging alternatives, sequential treatment appears promising. The adjunction of probiotics to conventional regimens, although eliciting great interest, has shown limited therapeutic benefit.