Analysis of drug resistance and virulence-factor genotype of Irish Helicobacter pylori strains: is there any relationship between resistance to metronidazole and cagA status?

Rapid diagnosis and precision treatment of Helicobacter pylori infection in clinical settings

Helicobacter pylori is a gram-negative bacterium that colonizes the stomach of approximately half of the worldwide population, with higher prevalence in densely populated areas like Asia, the Caribbean, Latin America, and Africa. H. pylori infections range from asymptomatic cases to potentially fatal diseases, including peptic ulcers, chronic gastritis, and stomach adenocarcinoma. The management of these conditions has become more difficult due to the rising prevalence of drug-resistant H. pylori infections, which ultimately lead to gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphoma. In 1994, the International Agency for Research on Cancer (IARC) categorized H. pylori as a Group I carcinogen, contributing to approximately 780,000 cancer cases annually. Antibiotic resistance against drugs used to treat H. pylori infections ranges between 15% and 50% worldwide, with Asian countries having exceptionally high rates. This review systematically examines the impacts of H. pylori infection, the increasing prevalence of antibiotic resistance, and the urgent need for accurate diagnosis and precision treatment. The present status of precision treatment strategies and prospective approaches for eradicating infections caused by antibiotic-resistant H. pylori will also be evaluated.

Antibiotic susceptibility pattern of Helicobacter pylori against eight antibiotics: A study from North India

BACKGROUND

The purpose of this analysis is to evaluate the antimicrobial susceptibility of eight drugs effective against Helicobacter pylori (H. pylori) strains and the genetic diversity of H. pylori virulence genes to foresee clinical outcomes in North India.

MATERIALS AND METHODS

Fifty-eight H. pylori strains isolated from patients suffering from various gastrointestinal (GI) diseases were included in the study. MICs of various antibiotics were determined by the agar dilution method. The chi-squared test and Fisher exact test were used to determine the p-value, which was considered significant at p-value ≤ 0.05. RStudio 4.0 was used to for the data visualization.

RESULTS

The prevalence of drug resistance was found to be: cefixime (CFM) (41.3%), furazolidone (FZD) (34.4%), amoxicillin (AMX) (20.7%), levofloxacin (LVFX) (70.7%), metronidazole (MTZ) (39.6%), tetracycline (TET) (20.7%), clarithromycin (CLA) (17.2%), and rifabutin (RIF) (17.2%). Out of 58 H. pylori strains, 3 were pan susceptible. There were H. pylori strains with single-drug resistance (21.8%, 12/55), dual resistance (30.9%, 17/55), triple resistance (20%, 11/55), and multidrug resistance (27.3%, 15/55). The resistance rate in MTZ, CLA and RIF were found to be significantly higher in females as compared to males (p = 0.005, p = 0.002, and p = 0.02), respectively. The resistance to TET exhibited significantly higher levels in gastritis compared to GERD, DU, and other disease groups (p = 0.04) respectively.

CONCLUSION

TET, AMX, CLA, and RIF were found to be more effective antibiotics against H. pylori infections, whereas more studies are required to provide evidence on increasing resistance rate of LVFX.

Relationship between antibiotic resistance and the cagA and vacA genotypes among Helicobacter pylori strain isolates from patients in Xi'an

The issue of drug resistance of Helicobacter pylori is becoming increasingly serious. To analyze the correlation between the cagA and vacA genotypes of H. pylori strains and their resistance to metronidazole, levofloxacin, and clarithromycin in patients in Xi'an, we studied 117 H. pylori strains isolated from patients in Xi'an. Antibiotic susceptibility testing of H. pylori was performed. The cagA and vacA genotypes were investigated using PCR. Among 117 strains of H. pylori, the rate of detection of cagA was 91.45% (107/117), among which the detection rate of East Asian-type cagA was 85.05% (91/107) and that of Western-type cagA was 14.95% (16/107). There were only two genotypes of vacA: s1m1 and s1m2. The detection rate of vacAs1m1 was 47.01% (55/117) and that of vacAs1m2 was 52.99% (62/117). The dominant strains in Xi'an were cagA + vacAs1m2 strains. The metronidazole resistance rate of vacAs1m2 H. pylori strains was significantly higher than that of vacAs1m1 H. pylori strains (91.94% vs. 69.09%, P = 0.002). The levofloxacin resistance rate of Western-type cagA strains was significantly higher than that of East Asian-type cagA strains (56.25% vs. 20.88%, P = 0.004). The metronidazole resistance rate of cagA + vacAs1m2 H. pylori strains was significantly higher than that of cagA + vacAs1m1 H. pylori strains (91.23% vs. 66.00%, P = 0.001). Our results showed that Western-type cagA strains were more likely to develop levofloxacin resistance than East Asian-type cagA strains. VacAs1m2 strains were more prone to metronidazole resistance than vacAs1m1 strains.

Helicobacter pylori Strains Isolated from Raw Poultry Meat in the Shahrekord Region, Iran: Frequency and Molecular Characteristics

Even though Helicobacter pylori (H. pylori) is a serious pathogen, its origin is unknown. Poultry (chicken, turkey, quail, goose, and ostrich) is consumed as a regular protein source by many people across the world; therefore, sanitary ways of delivering poultry for food are important for global health. As a result, the distribution of the virulence genes cagA, vacA, babA2, oipA, and iceA in H. pylori isolates in poultry meat, as well as their antibacterial resistance, was investigated. A Wilkins Chalgren anaerobic bacterial medium was used to cultivate 320 samples of raw poultry meat. Disk diffusion and multiplex-PCR were used to investigate both antimicrobial resistance and genotyping patterns. H. pylori was found in 20 of 320 (6.25 %) raw chicken meat samples. The highest incidence of H. pylori was found in chicken raw meat (15%), whereas no isolate was recovered from goose or quail raw meat (0.00%). Resistance to ampicillin (85%), tetracycline (85%), and amoxicillin (75%) were the most commonly detected in the tested H. pylori isolates. The percentage of H. pylori isolates with a multiple antibiotic resistance (MAR) index value of more than 0.2 was 17/20 (85%). The most prevalent genotypes detected were VacA (75%), m1a (75%), s2 (70%) and m2 (65%), and cagA (60%). The most typically detected genotype patterns were s1am1a (45 %), s2m1a (45 %), and s2 m2 (30%). babA2, oipA+, and oipA- genotypes were found in 40%, 30%, and 30% of the population, respectively. In summary, fresh poultry meat was polluted by H. pylori, with the babA2, vacA, and cagA genotypes being more prevalent. The simultaneous occurrence of vacA, cagA, iceA, oipA, and babA2 genotypes in antibiotic-resistant H. pylori bacteria raises a serious public health concern regarding the consumption of raw poultry. Future research should evaluate antimicrobial resistance among H. pylori isolates in Iran.

Molecular Mechanisms of Antibiotic Resistance and Novel Treatment Strategies for Helicobacter pylori Infections

Helicobacter pylori infects approximately 50% of the world's population and is considered the major etiological agent of severe gastric diseases, such as peptic ulcers and gastric carcinoma. Increasing resistance to standard antibiotics has now led to an ever-decreasing efficacy of eradication therapies and the development of novel and improved regimens for treatment is urgently required. Substantial progress has been made over the past few years in the identification of molecular mechanisms which are conducive to resistant phenotypes as well as for efficient strategies to counteract strain resistance and to avoid the use of ineffective antibiotics. These involve molecular testing methods, improved salvage therapies, and the discovery of novel and potent antimicrobial compounds. High rates of prevalence and gastric cancer are currently observed in Asian countries, including Japan, China, Korea, and Taiwan, where concomitantly intensive research efforts were initiated to explore advanced eradication regimens aimed at reducing the risk of gastric cancer. In this review, we present an overview of the known molecular mechanisms of antibiotic resistance and discuss recent intervention strategies for H. pylori diseases, with a view of the research progress in Asian countries.

Detection of A2143G, A2142C, and A2142G Point Mutations with Real-Time PCR in Stool Specimens from Children Infected with Helicobacter pylori

Reports have indicated an increasing prevalence of clarithromycin resistance in children relative to adults. Thus, it is important to investigate primary clarithromycin resistance before therapy to avoid treatment failure. A2142G, A2143G, and A2142C point mutations in the peptidyltransferase region of the 23S ribosomal RNA (rRNA) of Helicobacter pylori (H. pylori) strains isolated from children with gastrointestinal symptoms and asymptomatic children were evaluated via real-time polymerase chain reaction (RT-PCR) using fecal DNA samples. The presence of H. pylori was determined using a fecal H. pylori antigen enzyme-linked immunosorbent assay (ELISA) kit from the stools of children (n = 543). A2143G, A2142C, and A2142G point mutations were detected via RT-PCR and confirmed by sequencing the 23S rDNA. Fecal H. pylori antigen testing was positive in 101 symptomatic (49) and asymptomatic (52) children. A significant difference was found between the 0–5- and 5–18-year-old groups in terms of the A2143G and A2142G point mutations (p = 0.001). The A2142C mutation was not detected. There was a significant difference in the A2143G mutation between the symptomatic and asymptomatic 5–18-year-old children (p = 0.019). Macrolides are frequently used to treat upper respiratory tract infections in children due to their selective pressure effect. We suggest that H. pylori strains carrying mutations in the 23S RNA subunit conferring clarithromycin resistance may lead to an intense inflammatory response in the gastric epithelial cells, allowing them to proliferate more rapidly and causing possible diarrhea, halitosis, or abdominal pain in children.

Clinical relevance of the cagA and vacA s1m1 status and antibiotic resistance in Helicobacter pylori: a systematic review and meta-analysis

BACKGROUND

The role of Helicobacter pylori (H. pylori) virulence factors of such as vacA s1m1 and cagA in designating clinical outcomes and eradication rate has been deeply challenged in the last decade. The goal of this analysis was to identify the potential relevance between cagA and vacA genotypes with reported antibiotic resistance observed in clinical H. pylori isolates.

METHODS

This literature search was conducted in databases such as Clarivate analytics, PubMed, Scopus, EMBASE, DOAJ, and Google Scholar by April 2022, regardless of language restrictions and publication date. Quality of the included studies was assessed by the Newcastle-Ottawa scale. Statistical analysis of retrieved studies was fulfilled using Comprehensive Meta-Analysis software version 2.2. Following quality appraisal of eligible studies, potential association between the status of cagA and vacA genes with resistance to clarithromycin, metronidazole, amoxicillin, tetracycline, and levofloxacin was measured using odds ratio with 95% confidence interval. We also used sensitivity analyses and meta-regression to eliminate the source of heterogeneity from the overall estimates. Publication bias was assessed using funnel plot, Egger's test, Begg's test with the trim and fill procedure to assess the presence and magnitude of publication bias in the included studies.

RESULTS

Our findings suggested that a significant relationship between cagA status ‎and increase resistance ‎to metronidazole (OR: 2.69; 95% CI: 1.24-5.83‎‏‎). In subgroup analysis, we ‎found that in the Western ‎population, infection with cagA-positive strains could be led to increase in ‎the resistance to ‎metronidazole (OR: 1.59; 95% CI: ‎0.78-3.21‎‏‎), ‎amoxicillin (OR: ‎19.68‎; 95% CI: 2.74-‎‎141.18), ‎and ‎levofloxacin (OR: ‎11.33; 95% CI: ‎1.39-‎‎91.85). After implementation of trim and fill method, the adjusted OR was not significantly differed from original estimates which in turn represented our subgroup analysis was statistically robust. On the other hand, vacA ‎genotypes usually ‎reduce the antibiotic resistance of this bacterium, so that vacA s1m1 significantly reduces the ‎resistance to ‎metronidazole (OR: 0.41; 95% CI: 0.20-0.86‎‏‎). Surprisingly, resistance of vacA s2m2 strains to antibiotics was low, the reason may be due ‎to the non-inflammatory properties of strains containing vacA s2m2. The meta-regression and sensitivity analyses successfully reduced the effect of heterogeneity from the overall estimates. In addition, although the pooled OR is reduced after trim and fill adjustment but results do not change the conclusion regarding vacA genotypes and antibiotic resistance.

CONCLUSIONS

According to our findings, it was clearly demonstrated that cagA-positive strains are resistance to metronidazole, especially in Western countries. In Western countries, vacA s1m1 increases resistance to amoxicillin and levofloxacin. Based on the present findings, the vacA s1m1 genotype significantly increases resistance to metronidazole, while the vacA s1m2 decreases resistance to clarithromycin and metronidazole. Resistance to antibiotics in less virulent (vacA s2m2) strains is statistically significant lower than others.

In vitro anti-Helicobacter pylori activity of Syzygium aromaticum and the preliminary mechanism of action

ETHNOPHARMACOLOGICAL RELEVANCE

The dried flower bud of Syzygium aromaticum (L.) Merr. & L.M Perry (S. aromaticum) (Myrtaceae), also known as clove, was used in Traditional Chinese Medicine (TCM) to aid gastrointestinal function and treat stomach disorders including vomiting, flatulence and nausea. And it is a food homology medicine which is a promising candidate for H. pylori treatment. H. pylori is a Gram-negative bacterium that infects approximately 50% of the human population worldwide, which is closely related to multiple gastric diseases, including gastric cancer. However, there are still no sufficient studies on the anti-H. pylori activity of S. aromaticum, especially for the mechanism of action.

AIM OF STUDY

This study aimed to study the antibacterial activities of S. aromaticum extracts on both antibiotic-sensitive and -resistant H. pylori strains, and to explore the underlying mechanisms of action.

MATERIALS AND METHODS

The S. aromaticum extracts were obtained by heat reflux extraction and lyophilized to powder form. The phytochemical analyses were performed by High-performance liquid chromatography (HPLC) and UPLC-electrospray ionization mass spectrometry (ESI-MS). In vitro anti-H. pylori activity was evaluated by broth microdilution method. Mechanism of action studies included morphological observation using electron microscopy, determination of expression of virulence genes by reverse transcription quantitative polymerase chain reaction (RT-qPCR), genes expression profile identification by transcriptomic analysis, and exploration of anti-H. pylori infection mechanisms by network pharmacology analysis and western blotting validation.

RESULTS

The S. aromaticum extracts, aqueous extract (AE) and 75% hydroalcoholic extract (HE), exerted significant antibacterial activities against both antibiotic-sensitive and -resistant H. pylori strains with MICs of 160∼320 μg/ml, without developing drug resistance. Among them, AE was bactericide to all the tested strains with MBCs of less than 4MIC, while HE was merely bacteriostatic to most of the tested strains with MBCs of 2MIC∼16MIC. Besides, they showed no antagonistic effects in combination with clarithromycin, metronidazole, levofloxacin, and amoxicillin. Additionally, these extracts altered the morphology and ultrastructure and down-regulated the virulence genes expression of H. pylori. And transcriptomic analysis showed that they regulated genes expression of multiple H. pylori biological processes, including tricarboxylic acid cycle (TAC) and pyruvate metabolic pathways. Furthermore, these extracts combated the abnormal activation of PI3K-Akt and MAPK signaling pathways caused by H. pylori infection.

CONCLUSIONS

Overall, the present study firstly analyzed the chemical compositions of S. aromaticum extracts, and then confirmed their activities on both antibiotic-sensitive and -resistant H. pylori strains. In addition, the mechanisms of action of S. aromaticum extracts against H. pylori were found to be destroying the bacterial structure, down-regulating the expression of virulence genes, and interfering TAC and pyruvate metabolic pathways. Finally, S. aromaticum extracts were found to combated the abnormal activation of PI3K-Akt and MAPK signaling pathways to treat H. pylori infection. This study should accelerate further research and application of S. aromaticum against H. pylori infection.

Correlation between clarithromycin resistance, virulence factors and clinical characteristics of the disease in Helicobacter pylori infected patients in Shahrekord, Southwest Iran

The purpose of this study was to determine the mutations associated with clarithromycin resistance in Helicobacter pylori strains isolated from biopsy samples that were collected from the endoscopic ward of Shahrekord Hajar teaching Hospital and also to study the frequency of virulence factor and their correlation and pathological findings with clarithromycin resistance during the years 2019-2020. In this cross-sectional descriptive study, 152 patients with Helicobacter pylori infection were considered, and then, two common A2142G and A2143G mutations in the 23SrRNA gene associated with resistance were analyzed by Real-time PCR (Taq man). The presence of vacA, iceA1, iceA2, cagA, babA2, and oipA virulence genes was investigated by PCR and electrophoresis in 8% polyacrylamide gel. Then, data were analyzed using the relevant statistical tests. In this study, the frequency of Helicobacter pylori was 76% and the frequency of mutant isolates was 57.2%. The frequencies of A2142G and A2143G point mutations were 42.1% and 28.3%. There was a significant correlation among oipA, vacA, and iceA1 virulence factors, type of disease, chronic inflammatory score, and glandular atrophy with the antibiotic resistance to clarithromycin. There was no significant correlation between the age and sex of the patients with antibiotic resistance. According to the results of this study, it seems that the use of clarithromycin to combat this bacterium should be limited.

Helicobacter pylori Virulence Factor Genotyping

Helicobacter pylori (H. pylori) infection causes chronic gastritis, peptic ulcers, gastric adenocarcinoma, and mucosa-associated lymphoid tissue (MALT) lymphoma. Bacterial, host, and environmental factors influence the progression of disease from superficial gastritis to cancer. H. pylori is genetically diverse, and expression of its specific virulence factors has been linked to increased risk of more severe pathologies. Described in this chapter is a protocol for detecting important H. pylori virulence factors by firstly extracting DNA from culture material or stomach tissue biopsies, followed by PCR amplification and agarose gel electrophoresis.

Investigation of Clarithromycin Resistance-Associated Mutations and Virulence Genotypes of Helicobacter pylori Isolated from Iranian Population: A Cross-Sectional Study

Antibiotic resistance has brought into question the efficiency of clarithromycin which is a vital component of eradication therapy for Helicobacter pylori infection. The point mutations within the 23S rRNA sequence of H. pylori isolates which contribute to clarithromycin resistance have yet to be fully characterized. This study was aimed to detect clarithromycin resistance-associated mutations and assess the prevalence of key virulence factors of H. pylori among Iranian patients. Amplification of 16S rRNA and glmM genes were done to identify H. pylori. Minimal inhibitory concentration (MIC) of clarithromycin in 82 H. pylori clinical isolates was determined by agar dilution method. Subsequently, various virulence markers including cagA, vacA, sabA, babA, and dupA of H. pylori were identified by PCR. PCR-sequencing was applied to detect point mutations in the 23S rRNA gene. Based on MIC values, 43.9% of H. pylori isolates showed resistance to clarithromycin. The babA and cagA genes were detected in 92.7% and 82.9% of isolates, assigned to be higher than other virulence factors. No significant relationship was found between the H. pylori virulence genotypes and clarithromycin susceptibility (P > 0.05). Analyzing the 23S rRNA sequences revealed A2143G (4/48, 8.3%) and A2142G (3/48, 6.2%) as the most prevalent mutations in clarithromycin-resistant isolates. Additionally, several novel mutations including G2220T, C2248T, A2624C, G2287A, T2188C, G2710C, C2248T, G2269A, and G2224T were also detected among either resistant or susceptible isolates. Our findings revealed the presence of several point mutations in the 23S rRNA gene of H. pylori isolates which may be associated with resistance to clarithromycin.

Analysis of Correlation between the Seven Important Helicobacter pylori (H. pylori) Virulence Factors and Drug Resistance in Patients with Gastritis

The aim of this study is to evaluate the association between seven important H. pylori virulence factors and antibiotic resistance in patients with gastritis. H. pylori strains isolated from 33 patients with gastritis were examined. Antimicrobial susceptibilities were tested by GenoType® HelicoDR (Hain Life Science, Germany) test kit and RT-PCR. The virulence-factors were determined using conventional PCR. 39% of patients were resistant for clarithromycin and 27% of patients were resistant for fluoroquinolone. 15% of patients were resistant to both clarithromycin and fluoroquinolone. The H. pylori vacA m1/s2 genotype was the most frequent allelic combination. Patients were possessed the vacA s1, m1 (6.1%); s1, m2 (6.1%); s2, m1 (15.1%); and s2, m2 (3.0%) genotypes. 94% of patients with gastritis were positive for H. pylori napA gene. Also, there were no dupA gene-positive gastritis patients. There was no significant correlation between the vacA, cagA, oipA, hpaA, babA, napA, dupA, ureA, ureB virulence genes, clarithromycin, and fluoroquinolone resistance. Herein, we report that the relationship between the H. pylori napA gene and gastritis. Although we found a correlation between H. pylori virulence factor and clinical outcome, there is a need for further studies to enlighten the relation between H. pylori virulence genes and antibiotic resistance.

High Prevalence of Antibiotic Resistance in Iranian Helicobacter pylori Isolates: Importance of Functional and Mutational Analysis of Resistance Genes and Virulence Genotyping

The high prevalence of antibiotic resistance in Helicobacter pylori has become a great challenge in Iran. The genetic mutations that contribute to the resistance have yet to be precisely identified. This study aimed to investigate the prevalence of antibiotic resistance and virulence markers in Iranian H. pylori isolates and to analyze if there is any association between resistance and genotype. Antibiotic susceptibility patterns of 68 H. pylori isolates were investigated against metronidazole, clarithromycin, amoxicillin, rifampicin, ciprofloxacin, levofloxacin, and tetracycline by the agar dilution method. The frxA, rdxA, gyrA, gyrB, and 23S rRNA genes of the isolates were sequenced. The virulence genotypes were also determined using PCR. Metronidazole resistance was present in 82.4% of the isolates, followed by clarithromycin (33.8%), ciprofloxacin (33.8%), rifampicin (32.4%), amoxicillin (30.9%), levofloxacin (27.9%), and tetracycline (4.4%). Overall, 75% of the isolates were resistant to at least two antibiotics tested and considered as a multidrug resistance (MDR) phenotype. Most of the metronidazole-resistant isolates carried frameshift mutations in both frxA and rdxA genes, and premature termination occurred in positions Q5Stop and Q50Stop, respectively. Amino acid substitutions M191I, G208E, and V199A were predominantly found in gyrA gene of fluoroquinolone-resistant isolates. A2143G and C2195T mutations of 23S rRNA were found in four clarithromycin-resistant isolates. Interestingly, significant associations were found between resistance to metronidazole (MNZ) and cagA-, sabA-, and dupA-positive genotypes, with p = 0.0002, p = 0.0001, and p = 0.0001, respectively. Furthermore, a significant association was found between oipA “on” status and resistance to amoxicillin (AMX) (p = 0.02). The prevalence of H. pylori antibiotic resistance is high in our region, particularly that of metronidazole, clarithromycin, ciprofloxacin, and MDR. Simultaneous screening of virulence and resistance genotypes can help clinicians to choose the appropriate therapeutic regime against H. pylori infection.

Molecular mechanism of Helicobacter pylori-induced autophagy in gastric cancer

Helicobacter pylori (H. pylori) is a gram-negative pathogen that colonizes gastric epithelial cells. The drug resistance rates of H. pylori have dramatically increased, causing persistent infections. Chronic infection by H. pylori is a critical cause of gastritis, peptic ulcers and even gastric cancer. In host cells, autophagy is stimulated to maintain cellular homeostasis following intracellular pathogen recognition by the innate immune defense system. However, H. pylori-induced autophagy is not consistent during acute and chronic infection. Therefore, a deeper understanding of the association between H. pylori infection and autophagy in gastric epithelial cells could aid the understanding of the mechanisms of persistent infection and the identification of autophagy-associated therapeutic targets for H. pylori infection. The present review describes the role of H. pylori and associated virulence factors in the induction of autophagy by different signaling pathways during acute infection. Additionally, the inhibition of autophagy in gastric epithelial cells during chronic infection was discussed. The present review summarized H. pylori-mediated autophagy and provided insights into its mechanism of action, suggesting the induction of autophagy as a novel therapeutic target for persistent H. pylori infection.

Phenotypic analysis of antibiotic resistance and genotypic study of the vacA, cagA, iceA, oipA and babA genotypes of the Helicobacter pylori strains isolated from raw milk

Background

Foods with animal origins and particularly milk play a considerable role in transmission of Helicobacter pylori. The current study was performed to assess phenotypic characters of antibiotic resistance and genotyping pattern of vacA, cagA, iceA, oipA and babA2 alleles amongst the H. pylori strains isolated from raw milk.

Methods

Six-hundred and thirty raw milk samples were collected and cultured on Wilkins Chalgren anaerobe media. Antibiotic resistance and genotyping patterns were studied using disk diffusion and PCR, respectively.

Results

Sixty-seven out of 630 (10.63%) raw milk samples were positive for H. pylori. Ovine raw milk (17.27%) samples had the highest prevalence of H. pylori, while camel (5.00%) had the lowest. H. pylori strains harbored the highest prevalence of resistance against ampicillin (82.08%), tetracycline (76.11%), amoxicillin (74.62%), metronidazole (65.67%) and erythromycin (53.73%). Prevalence of resistance against more than 10 types of antibiotics was 17.91%. VacA s1a (83.58%), m1a (80.59%), s2 (77.61%) and m2 (68.65%), cagA (73.13%) and babA2 (44.77%) were the most commonly detected genotypes. We found that S1am1a (56.71%), s2m1a (56.71%), s1 am2 (43.28%) and s2 m2 (43.28%) were the most commonly detected genotyping pattern. Frequency of cagA-, oipA- and babA2- genotypes were 26.86%, 62.68% and 55.22%, respectively. We found that S1a/cagA+/iceA1/oipA-/babA2- (28.35%), m1a/cagA+/iceA1/oipA-/babA2- (28.35%) and s2/cagA+/iceA1/oipA-/babA2- (26.86%) were the most commonly detected combined genotyping pattern.

Conclusions

Simultaneous presence of vacA, cagA, iceA, oipA and babA2 genotypes in antibiotic resistant H. pylori strains indicates important public health issue regarding the consumption of raw milk. However, additional researches are required to find molecular genetic homology and other epidemiological aspects of H. pylori in milk.

Can bacterial virulence factors predict antibiotic resistant Helicobacter pylori infection?

AIM

To evaluate the association between virulence factor status and antibiotic resistance in Helicobacter pylori (H. pylori)-infected patients in Ireland.

METHODS

DNA was extracted from antral and corpus biopsies obtained from 165 H. pylori-infected patients. Genotyping for clarithromycin and fluoroquinolone-mediating mutations was performed using the Genotype HelicoDR assay. cagA and vacA genotypes were investigated using PCR.

RESULTS

Primary, secondary and overall resistance rates for clarithromycin were 50.5% (n = 53/105), 78.3% (n = 47/60) and 60.6% (n = 100/165), respectively. Primary, secondary and overall resistance rates for fluoroquinolones were 15.2% (n = 16/105) and 28.3% (n = 17/60) and 20% (n = 33/165), respectively. Resistance to both antibiotics was 12.4% (n = 13/105) in treatment-naïve patients, 25% (n = 15/60) in those previously treated and 17% (n = 28/165) overall. A cagA-positive genotype was detected in 22.4% (n = 37/165) of patient samples. The dominant vacA genotype was S1/M2 at 44.8% (n = 74/165), followed by S2/M2 at 26.7% (n = 44/165), S1/M1 at 23.6% (n = 39/165) and S2/M1 at 4.8% (n = 8/165). Primary clarithromycin resistance was significantly lower in cagA-positive strains than in cagA-negative strains [32% (n = 8/25) vs 56.3% (n = 45/80) P = 0.03]. Similarly, in patients infected with more virulent H. pylori strains bearing the vacA s1 genotype, primary clarithromycin resistance was significantly lower than in those infected with less virulent strains bearing the vacA s2 genotype, [41% (n = 32/78) vs 77.8% (n = 21/27) P = 0.0001]. No statistically significant association was found between primary fluoroquinolone resistance and virulence factor status.

CONCLUSION

Genotypic H. pylori clarithromycin resistance is high and cagA-negative strains are dominant in our population. Less virulent (cagA-negative and vacA S2-containing) strains of H. pylori are associated with primary clarithromycin resistance.

Helicobacter pylori treatment: antibiotics or probiotics

Treatment of Helicobacter pylori infection is important for the management of gastrointestinal disorders such as peptic ulcer and gastric cancer. Due to the increase in the prevalence of H. pylori resistance to antibiotics, triple therapy with clarithromycin is no longer the best treatment for H. pylori, especially in some areas where the local resistance to this antibiotic is higher than 20%. Alternative treatments have been proposed for the eradication of H. pylori. Some of them including novel antibiotics or classical ones in different combinations; these treatments are being used in the regular clinical practice as novel and more effective treatments. Others therapies are using probiotics associated to antibiotics to treat this infection.The present article is a revision of H. pylori eradication treatment, focusing on emerging approaches to avoid the treatment failure, using new therapies with antimicrobials or with probiotics.

Prevalence of clarithromycin-resistant Helicobacter pylori strains in gastric mucosa-associated lymphoid tissue lymphoma patients

Gastric MALT lymphoma is closely associated with Helicobacter pylori infection. Bacterial eradication therapy comprising clarithromycin is the first-line treatment in gastric MALT lymphoma patients. However, antimicrobial resistance to clarithromycin has been increasing in Europe, and thus far, it has not been examined in gastric MALT lymphoma patients. Based upon histopathological investigation, 17 adult gastric MALT lymphoma patients were identified to be related with H. pylori infection between 1997 and 2014. Detection of H. pylori infection in these patients and clarithromycin susceptibility testing were performed by 23S rRNA gene real-time PCR. Twelve of the patients were confirmed with H. pylori infection by real-time PCR. Among these patients, only two were found to be infected with clarithromycin-resistant H. pylori strain. In one of them, both the clarithromycin-resistant and sensitive genotype were detected. The rate of clarithromycin resistance was 15.4 %. Clarithromycin resistance pattern in gastric MALT lymphoma patients is under the predictions since a previous study performed in Central Europe revealed a rate of 36.6 % in Austria. Considering the low antimicrobial resistance rate, clarithromycin is still an option in gastric MALT lymphoma management.

The Primary Resistance of Helicobacter pylori in Taiwan after the National Policy to Restrict Antibiotic Consumption and Its Relation to Virulence Factors-A Nationwide Study

Objective

The Taiwan Government issued a policy to restrict antimicrobial usage since 2001. We aimed to assess the changes in the antibiotic consumption and the primary resistance of H. pylori after this policy and the impact of virulence factors on resistance.

Methods

The defined daily dose (DDD) of antibiotics was analyzed using the Taiwan National Health Insurance (NHI) research database. H. pylori strains isolated from treatment naïve (N=1395) and failure from prior eradication therapies (N=360) from 9 hospitals between 2000 and 2012 were used for analysis. The minimum inhibitory concentration was determined by agar dilution test. Genotyping for CagA and VacA was determined by PCR method.

Results

The DDD per 1000 persons per day of macrolides reduced from 1.12 in 1997 to 0.19 in 2008, whereas that of fluoroquinolones increased from 0.12 in 1997 to 0.35 in 2008. The primary resistance of amoxicillin, clarithromycin, metronidazole, and tetracycline remained as low as 2.2%, 7.9%, 23.7%, and 1.9% respectively. However, the primary levofloxacin resistance rose from 4.9% in 2000–2007 to 8.3% in 2008–2010 and 13.4% in 2011–2012 (p=0.001). The primary resistance of metronidazole was higher in females than males (33.1% vs. 18.8%, p<0.001), which was probably attributed to the higher consumption of nitroimidazole. Neither CagA nor VacA was associated with antibiotic resistance.

Conclusions

The low primary clarithromycin and metronidazole resistance of H. pylori in Taiwan might be attributed to the reduced consumption of macrolides and nitroimidazole after the national policy to restrict antimicrobial usage. Yet, further strategies are needed to restrict the consumption of fluoroquinolones in the face of rising levofloxacin resistance.

Analysis of clinical isolates of Helicobacter pylori in Pakistan reveals high degrees of pathogenicity and high frequencies of antibiotic resistance

BACKGROUND

Antibiotic resistance in Helicobacter pylori contributes to failure in eradicating the infection and is most often due to point and missense mutations in a few key genes.

METHODS

The antibiotic susceptibility profiles of H. pylori isolates from 46 Pakistani patients were determined by Etest. Resistance and pathogenicity genes were amplified, and sequences were analyzed to determine the presence of mutations.

RESULTS

A high percentage of isolates (73.9%) were resistant to metronidazole (MTZ), with considerable resistance to clarithromycin (CLR; 47.8%) and amoxicillin (AML; 54.3%) also observed. Relatively few isolates were resistant to tetracycline (TET; 4.3%) or to ciprofloxacin (CIP; 13%). However, most isolates (n = 43) exhibited resistance to one or more antibiotics. MTZ-resistant isolates contained missense mutations in oxygen-independent NADPH nitroreductase (RdxA; 8 mutations found) and NADH flavin oxidoreductase (FrxA; 4 mutations found). In the 23S rRNA gene, responsible for CLR resistance, a new point mutation (A2181G) and 4 previously reported mutations were identified. Pathogenicity genes cagA, dupA, and vacA s1a/m1 were detected frequently in isolates which were also found to be resistant to MTZ, CLR, and AML. A high percentage of CagA and VacA seropositivity was also observed in these patients. Phylogenetic analysis of partial sequences showed uniform distribution of the 3' region of cagA throughout the tree.

CONCLUSIONS

We have identified H. pylori isolates in Pakistan which harbor pathogenicity genes and worrying antibiotic resistance profiles as a result of having acquired multiple point and missense mutations. H. pylori eradication regimens should therefore be reevaluated in this setting.

CagA status & genetic characterization of metronidazole resistant strains of H. pylori from: A region at high risk of gastric cancer

Objective: The aim of study was to determine relationship between cagA and genetic characterization of metronidazole (MTZ) resistant H. pylori strains from a region at high risk of gastric cancer.

Methods: 172 H. pylori strains were isolated from the patients with dyspeptic symptoms, and antimicrobial susceptibility testing for MTZ was assessed by E-test. rdxA and frxA genes were amplified using PCR among the MTZ resistant isolates. The status of the plasmid and classes 1～3 integrons were investigated in all isolates.

Results: MTZ was detected in 88 isolates (51.16%). Variations in the rdxA gene leading to alterations of amino acids in RdxA proteins were identified in all MTZ resistant strains. FrxA contained missense alterations in 55 MTZ resistant isolates, while the premature truncation of FrxA was caused by frameshift mutations in 9 MTZ resistant strains. Plasmid was found in one MTZ sensitive strain (0.58%), and none of Class 1～3 integrases gene was detected in the studied isolates. The conservative cagA fragment was obtained from all clinical isolates of H. pylori. The sequence of cagA 3' variable region in 164 strains were obtained, including East Asian-type (122, 74.39%) and Western-type (42, 25.61%). Prevalence of Western-type cagA 3' variable region was significantly higher in MTZ resistant (33.73%, 28/83) than those of MTZ-sensitive strains (17.28%, 14/81) (p=0.02).

Conclusion: A high prevalence of MTZ resistance was found in the region, and bacterial chromosome mutations in the rdxA and frxA gene still contribute to the high-level MTZ resistance. H. pylori strains characterized with West-type cagA 3’ variable region tend to acquire MTZ resistance in the region.

Rational Helicobacter pylori therapy: evidence-based medicine rather than medicine-based evidence

Data are available such that choice of Helicobacter pylori therapy for an individual patient can be reliably predicted. Here, treatment success is defined as a cure rate of 90% or greater. Treatment outcome in a population or a patient can be calculated based on the effectiveness of a regimen for infections with susceptible and with resistant strains coupled with the knowledge of the prevalence of resistance (ie, based on formal measurement, clinical experience, or both). We provide the formula for predicting outcome and we illustrate the calculations. Because clarithromycin-containing triple therapy and 10-day sequential therapy are now only effective in special populations, they are considered obsolete; neither should continue to be used as empiric therapies (ie, 7- and 14-day triple therapies fail when clarithromycin resistance exceeds 5% and 15%, respectively, and 10-day sequential therapy fails when metronidazole resistance exceeds 20%). Therapy should be individualized based on prior history and whether the patient is in a high-risk group for resistance. The preferred choices for Western countries are 14-day concomitant therapy, 14-day bismuth quadruple therapy, and 14-day hybrid sequential-concomitant therapy. We also provide details regarding the successful use of fluoroquinolone-, rifabutin-, and furazolidone-containing therapies. Finally, we provide recommendations for the efficient development (ie, identification and optimization) of new regimens, as well as how to prevent or minimize failures. The trial-and-error approach for identifying and testing regimens frequently resulted in poor treatment success. The described approach allows outcome to be predicted and should simplify treatment and drug development.

Epidemiology and pattern of antibiotic resistance in Helicobacter pylori: scenario from Saudi Arabia

Helicobacter pylori is recognized as a major cause of gastritis, peptic ulcer, gastric cancer, and mucosa-associated lymphoma. Infection with this gram-negative microaerophile has been treated using combination of antibiotics and proton pump inhibitors for different gastrointestinal diseases. The most commonly used treatment is triple therapy which consists of administration of a proton pump inhibitor, clarithromycin, and amoxicillin. Many factors contribute to treatment failure, but one of the main reasons is development of bacterial antibiotic resistance. The percent prevalence of antibiotic resistance varies among different countries; it appears to be partly determined by the geographic factors and its ability to undergo frequent homologous recombination. The aim of this paper is to review the prevalence of H. pylori infection, association of clinical outcomes with H. pylori genotypes, and current status of antibiotic resistance in H. pylori in Saudi Arabia. It also discusses the different alternative approaches for the treatment of H. pylori using antibiotics. In addition, association of antibiotic resistance with H. pylori virulent genotypes in Saudi population and its underlying resistance mechanism will also be discussed.

Antibiotic resistance and cagA gene correlation: A looming crisis of Helicobacter pylori

AIM: To determine antibiotic resistance of Helicobacter pylori (H. pylori) in Pakistan and its correlation with host and pathogen associated factors.

METHODS: A total of 178 strains of H. pylori were isolated from gastric biopsies of dyspeptic patients. Susceptibility patterns against first and second-line antibiotics were determined and trends of resistance were analyzed in relation to the sampling period, gastric conditions and cagA gene carriage. The effect of cagA gene on the acquisition of resistance was investigated by mutant selection assay.

RESULTS: The observations showed that monoresistant strains were prevalent with rates of 89% for metronidazole, 36% for clarithromycin, 37% for amoxicillin, 18.5% for ofloxacin and 12% for tetracycline. Furthermore, clarithromycin resistance was on the rise from 2005 to 2008 (32% vs 38%, P = 0.004) and it is significantly observed in non ulcerative dyspeptic patients compared to gastritis, gastric ulcer and duodenal ulcer cases (53% vs 20%, 18% and 19%, P = 0.000). On the contrary, metronidazole and ofloxacin resistance were more common in gastritis and gastric ulcer cases. Distribution analysis and frequencies of resistant mutants in vitro correlated with the absence of cagA gene with metronidazole and ofloxacin resistance.

CONCLUSION: The study confirms the alarming levels of antibiotic resistance associated with the degree of gastric inflammation and cagA gene carriage in H. pylori strains.

Key points for designing and reporting Helicobacter pylori therapeutic trials: a personal view

BACKGROUND & OBJECTIVES

The aim of this document is to provide a methodological framework and to review key aspects for adequately designing trials to evaluate new treatments for Helicobacter pylori infection.

METHODS

Non-systematic literature review.

RESULTS & CONCLUSIONS

Regarding the design of the article, we suggest selecting for future trials drugs to which H. pylori has no significant primary resistances and evaluating therapies with pilot studies before engaging in randomized trials. The manuscript defines how the number and type of H. pylori diagnostic tests necessary before and after the trial depend on the setting and reliability of the tests. It recommends the best methods and timing for H. pylori testing before and after therapy. Other recommendations are using current standard treatments as comparators of new therapies, determining antibiotic sensitivity - whenever useful and possible - using adequate randomization and allocation concealment but not necessarily blinding, and performing an intention-to-treat and a per-protocol analysis. In addition, we give basic tips for reporting and discussing study results.

Numerous risk factors for Helicobacter pylori antibiotic resistance revealed by extended anamnesis: a Bulgarian study

The aim of this study was to assess risk factors for primary Helicobacter pylori antibiotic resistance by an extended anamnesis. In total, 519 H. pylori strains from untreated symptomatic adults who answered a questionnaire were evaluated. Strain susceptibility was assessed by a breakpoint susceptibility test. Primary resistance rates were 29.5 % for metronidazole, 17.9 % for clarithromycin, 7.3 % for metronidazole+clarithromycin, 4.0 % for tetracycline and 10.8 % for ciprofloxacin. On multivariate analysis, younger (≤65 years) age was an independent predictor for metronidazole resistance. To our knowledge, for the first time, being a member of the health-care profession was revealed as a risk factor for H. pylori resistance to metronidazole and both metronidazole and clarithromycin. Respiratory and urinary tract infections were independent predictors of clarithromycin and ciprofloxacin resistance, respectively. The presence of co-infections was an independent risk factor for clarithromycin, metronidazole and ciprofloxacin resistance. Surprisingly, female sex was the only predictor for tetracycline resistance. The antibiotic resistance rates were not associated with disease type, place of residence, birthplace, educational level, non-steroidal anti-inflammatory drug or proton pump inhibitor use, smoking or dietary factors, such as consumption of coffee, yogurt, green tea, raw garlic, raw onion, honey or meat. There was a trend for higher metronidazole resistance in strains from diabetic patients. In conclusion, the extended anamnesis of H. pylori-positive patients should include data on patient age, sex, whether they are in the health-care profession, co-infections and possibly diabetes to improve the choice of empiric therapy. Tailored treatment based on the extended anamnesis is suggested, and susceptibility testing of the strains is recommended for patients at risk for antibiotic resistance, especially to clarithromycin, fluoroquinolones or both metronidazole and clarithromycin.

CagA genotype and metronidazole resistant strain of Helicobacter pylori in functional dyspepsia in Thailand

BACKGROUND AND AIM

Many previous studies indicated relationship between H. pylori infection and functional dyspepsia (FD) but pathogenesis remains unclear. The aim of this study was to determine relationship between cagA genotype and metronidazole resistant strains of H. pylori in Thai FD patients.

METHODS

Total of 412 Thai FD patients who underwent gastroscopy at Thammasat University Hospital, Thailand between June 2008 and May 2010 were enrolled. Two antral gastric biopsies were obtained for CLO test, cultures and E-test for metronidazole. Cag A genotype was determined by PCR. FD patients were diagnosed by Rome III criteria and categorized as epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS).

RESULTS

133 FD patients (31%) were infected with H. pylori (56 male, 77 female). There were 37 patients with EPS and 96 patients with PDS. Cag A genotype was performed in 114 patients and CagA 1a was demonstrated in 24.6%. Cag A 1a was relatively higher prevalence in PDS than EPS without statistical significance (26% vs 22%; P > 0.05). E-test for metronidazole was performed in 100 patients (32 EPS and 68 PDS patients) and metronidazole resistant strains were found in 30%. Metronidazole resistant strains were significantly higher in PDS than EPS patients (38.2% vs 12.5%; P = 0.03). In EPS patients, presence of cagA 2a gene was significantly higher in metronidazole resistant than metronidazole sensitive strains (100% vs 74.1%; OR = 4.8, 95% CI = 1.2-26.8, P = 0.01).

CONCLUSIONS

PDS was the predominant type of FD in Thailand. Metronidazole resistant strains and cagA 2a gene of H. pylori infection was commonly found in Thai FD patients. In EPS patients, cagA 2a gene might be related to metronidazole resistant strains of H. pylori infection in Thailand.

Is there a benefit to extending the duration of Helicobacter pylori sequential therapy to 14 days?

BACKGROUND AND AIMS

 Ten-day sequential therapy with a proton-pump inhibitor (PPI) and amoxicillin followed by a PPI, clarithromycin, and an imidazole typically achieves Helicobacter pylori (H. pylori) eradication rates between 90 and 94% (i.e., Grade B success). It has been suggested that prolonging the duration of therapy might improve the treatment success. We tested whether prolonging treatment duration to 14-days would improve the results to 95% or greater eradication.

METHODS

 This was a multi-center, single site, pilot study in which H. pylori-infected patients received a 14-day sequential therapy (esomeprazole and amoxicillin for 7 days followed by esomeprazole, clarithromycin, and metronidazole for 7 days). H. pylori status was assessed 8 weeks after therapy. Success was defined as achieving 95% or greater eradication by per-protocol (PP) analysis.

RESULTS

  One hundred and twenty-three subjects received the 14-day sequential therapy. The eradication rate was 93.9% (95% confidence interval [CI], 89.5-98.3%) by PP and 91.9% (95% CI, 87.1-96.7%) by intention-to-treat analysis. Adverse events were experienced by 21.1%; compliance of 90% or greater was 95.9%.

CONCLUSIONS

 Extending sequential therapy to 14 days did not result in improving the treatment outcome to 95% or greater.

High prevalence of clarithromycin-resistant Helicobacter pylori strains and risk factors associated with resistance in Madrid, Spain

Clarithromycin is one of the antibiotics used for the treatment of Helicobacter pylori infections, and clarithromycin resistance is the most important factor when it comes to predicting eradication failure. The present study analyzed H. pylori isolates for the presence of 23S rRNA gene mutations and determined the risk factors associated with resistance among H. pylori isolates collected in Madrid, Spain, in 2008. We studied 118 H. pylori strains isolated from the same number of patients. A total of 76.3% of the patients were born in Spain, 52.7% were children, 20.3% had previously been treated, and 66.1% were female. Clarithromycin resistance was determined by Etest. H. pylori strains were considered resistant if the MIC was ≥1 mg/liter. DNA extraction was carried out by use of the NucliSens easyMAG platform with NucliSens magnetic extraction reagents (bioMérieux). The DNA sequences of the 23S rRNA genes of clarithromycin-resistant and -sensitive strains were determined to identify specific point mutations. The vacA genotype and cagA status were determined by PCR. We found that 42 (35.6%) strains were resistant to clarithromycin by Etest. Etest results were confirmed by detection of the presence of point mutations in 34 (88.1%) of these strains. Eight H. pylori strains were resistant to clarithromycin by Etest but did not have a point mutation in the 23S rRNA gene. Mutation at A2143G was found in 85.3% of the strains, mutation at A2142G in 8.8%, and mutation at T2182C in 5.9%. Dual mutations were found in 8.8% of the strains. H. pylori clarithromycin-resistant strains were strongly associated with pediatric patients, with patients born in Spain, and with patients who had previously been treated (P ≤ 0.02). In addition, H. pylori strains resistant to clarithromycin more frequently presented the vacA s2/m2 genotype and were more likely to be cagA negative than susceptible strains (39.1% and 11.2%, respectively; P value < 0.001). We concluded that, in the present study, H. pylori clarithromycin-resistant strains are more frequently found in children, in patients mostly born in Spain, and in individuals who were previously treated for H. pylori infection and that these individuals are more likely colonized with a less virulent H. pylori strain.