Molecular resistance testing of Helicobacter pylori in gastric biopsies

Characterization of Domain V Mutations in Clinical Isolates of Helicobacter pylori in Pakistan and Their Effect on Clarithromycin MIC

PURPOSE

Clarithromycin is commonly prescribed for H. pylori infection. Domain V mutations are responsible for clarithromycin resistance. This study was aimed to characterize the clarithromycin resistance and its associated mutations in clinical isolates of H. pylori in Pakistan.

MATERIALS AND METHODS

Infection was diagnosed in 93 patients' biopsies using culture, rapid urease test, 16S rRNA, and vacA gene multiplex PCR. Clarithromycin resistance was assessed by the agar dilution method. Mutations were detected by PCR-RFLP using 46 (1.4 kb) domain V fragments. Sequencing was executed for 13 domain V fragments, of which 12 showed unusual amplicon size (1.2 kb) and 01 had a new MboII RFLP pattern.

RESULTS

A total of 48 (83%) strains were obtained from 58 (62.3%) PCR H. pylori-positive samples. Resistance (MIC ≥ 0.001 mg/mL) and intermediate resistance phenotype (MIC = 0.0005 mg/mL) was observed in 22 (46%), and 10 (21%) isolates, respectively. The primary resistance was found in 23 (39.6%) samples. PCR-RFLP detected A2142G, A2143G, and double mutations in 19, 04, and 01 resistant strain, respectively. Sequencing of 10 amplicons obtained from intermediated resistant strains and 03 amplicons from resistant strains showed 138 new mutations. Among them, T2182C was also seen in 04 intermediated resistant isolates, whereas A2142G, A2143G, and A2143C were observed in resistant isolates. The new MboII RFLP pattern in an intermediated resistant strains was due to A1761G mutation.

CONCLUSION

H. pylori domain V mutations showed extensive diversity. Multiple mutations in domain V may give endurance to H. pylori against clarithromycin. Further investigations on the molecular mechanism of antibiotic resistance in H. pylori seem crucial at this stage.

Multiplex PCR for detection of Helicobacter pylori infection in gastric biopsies with lower inflammatory score

BACKGROUND

No gold standard has yet been established for the diagnosis of H. pylori infection. A multiplex polymerase chain reaction (mPCR) was developed in this study for rapid, sensitive and specific detection of H. pylori from gastric biopsies.

METHODS

H. pylori infections were determined by in-house rapid urease test (iRUT), culture, histology and multiplex PCR.

RESULTS

A total of 140 (60.9%) from 230 patients were positive for H. pylori infection. H. pylori were detected in 9.6% (22/230), 17% (39/230), 12.6% (29/230) and 60% (138/230) of biopsy specimens by culture, iRUT, histology and mPCR, respectively. mPCR identified H. pylori infection in 100% of biopsies with positive histology and culture. All biopsies with positive iRUT yielded positive PCR except two cases. mPCR also detected H. pylori in additional 116, 101 and 109 biopsies that were negative by culture, iRUT and histology, respectively. Positive samples by mPCR showed lower average in H. pylori density, activity and inflammation scores. The Indians showed the highest prevalence of H. pylori infection compared to the Chinese and the Malays. In addition, Chinese patients with older age were significantly infected compared to other ethnicities.

CONCLUSION

PCR was able to detect the highest numbers of positive cases although the lowest average scores were recorded in the activity, inflammatory and H. pylori density.

High Frequency of vacA s1m2 Genotypes Among Helicobacter pylori Isolates From Patients With Gastroduodenal Disorders in Kermanshah, Iran

Background:

Helicobacter pylori infection and related diseases outcome are mediated by a complex interplay between bacterial, host and environmental factors. Several distinct virulence factors of H. pylori have been shown to be associated with different clinical outcomes. Here we focused on vacA and cagA genotypes of H. pylori strains isolated from patients with gastric disorder.

Objectives:

The aim of this study was to determine the frequency of two toxins and genotypes of VacA toxin in patients referred to a central hospital in the west of Iran (Imam Reza hospital, Kermanshah) during 2011 - 2012.

Patients and Methods:

Samples were collected from patients infected with H. pylori. Gastric biopsy specimens from the stomach antrum and corpus were cultured. PCR analysis was performed for genotyping H. pylorivacA and cagA genes.

Results:

Helicobacter pylori was isolated from 48% (96/200) of patients with gastroduodenal disorders. In 81/96 (84%) cases, the cagA gene was present. Among different genotypes of vacA, two s1m2 and s2m2 genotypes were dominant with frequency of 39.5% and 50%, respectively. The frequency of the s1m1 genotype was 7.2% (7/96), which is much lower than elsewhere. H. pylori isolates with positive results for cagA gene and vacA s1m2 genotypes showed statistically significant correlation with peptic ulcer (s1m2 13/34 [38.2%] P = 0.003). However, isolates of H. pylori infection with cagA gene and vacAs2m2 genotypes were significantly associated with development of gastritis (s2m2 41/42 [97.6%] P = 0.000).

Conclusions:

About 90% of H. pylori strains potentially contained vacAs2m2 and s1m2 genotypes. Infection with H. pylori strain containing the cagA gene or the vacAs1m1 and s1m2 genotypes was associated with increased incidence of peptic ulcer disease (PUD).

Levofloxacin-based triple therapy vs. quadruple therapy in second-line Helicobacter pylori treatment: a randomized trial

BACKGROUND

Levofloxacin has been shown to be effective in Helicobacter pylori eradication. Two 10-day levofloxacin-based triple therapies were compared with standard 7- and 14-day quadruple regimens in second-line treatment.

METHODS

Two hundred and eighty consecutive patients who failed to respond to standard triple therapy (clarithromycin, amoxicillin, rabeprazole) were randomly assigned to four groups: (1) levofloxacin 500 mg o.d., amoxicillin 1 g b.d., rabeprazole 20 mg b.d. for 10 days (LAR, n = 70); (2) levofloxacin 500 mg o.d., tinidazole 500 mg b.d., rabeprazole 20 mg b.d. for 10 days (LTR, n = 70); (3) tetracycline 500 mg q.d.s., metronidazole 500 mg t.d.s., bismuth salt 120 mg q.d.s., rabeprazole 20 mg b.d. for 7 days (7TMBR, n = 70); and (4) for 14 days (14TMBR, n = 70). Helicobacter pylori status and side-effects were assessed 6 weeks after treatment.

RESULTS

The eradication rate was 94% in the LAR group and 90% in the LTR group in both intention-to-treat and per protocol analyses. Helicobacter pylori eradication was achieved in 63 and 69% of the 7TMBR group and in 69 and 80% of the 14TMBR group in intention-to-treat and per protocol analysis, respectively. Side-effects were significantly lower in the LAR and LTR groups than in the 14TMBR group.

CONCLUSION

Ten-day levofloxacin-based therapies are better than standard quadruple regimens as second-line option for H. pylori eradication.

Molecular evidence of Helicobacter cinaedi organisms in human gastric biopsy specimens

One hundred twenty-six urease-negative gastric biopsy specimens were evaluated for the presence of Helicobacter genus-specific 16S ribosomal DNA (rDNA) and H. pylori-specific glmM DNA sequences by PCR. The species specificity of the glmM PCR assay was demonstrated, as H. pylori was the only Helicobacter species that yielded the expected glmM amplicon. Most urease-negative specimens (118 of 126 specimens) lacked Helicobacter DNA. However, 8 of 126 urease-negative specimens contained Helicobacter 16S rDNA. In order to identify the Helicobacter species present in urease-negative gastric biopsy specimens, 16S rDNA amplicons were cloned and sequenced. Sequence comparisons were performed by analyses of the sequences in public sequence databases. Two samples contained 16S rDNA that was identified as H. cinaedi with 100% identity and that spanned approximately 400 bp (398 and 398 bp, respectively). In contrast, multiple differences (97% identity; 390 of 398 bp) were observed with H. pylori 16S rDNA in this region. This finding was verified by sequencing an overlapping 537-bp fragment within the 5' portion of 16S rDNA. Although the clinical findings were consistent with H. pylori infection (e.g., duodenal ulcer disease), rapid urease testing and DNA sequence analyses suggested the presence of H. cinaedi organisms and the absence of H. pylori in two human antral biopsy specimens. This study represents the first report of an enteric urease-negative helicobacter in the human stomach. Although these organisms were previously associated with extragastric infections, the roles of these organisms in the pathogenesis of chronic gastritis or peptic ulcer disease remain unclear.

Phosphorylation of Helicobacter pylori CagA in patients with gastric ulcer and gastritis

The effects of Helicobacter pylori infection are strongly associated with chronic gastritis, gastric and duodenal ulcer, gastric cancer, and MALT lymphoma. The microorganism has been classified as a type I carcinogen by the World Health Organization. Varying clinical results from H. pylori infection are believed due, in part, to differences in virulence among species. The cag pathogenicity island is a complex of virulent genes and a coding region for the type IV phosphorylated secretion system. Through this system, many virulent gene products or proteins are phosphorylated into the host cells. This study demonstrated the positive CagA-phosphorylation effect of H. pylori in patients with chronic gastritis and benign gastric ulcer and revealed significantly different rates of CagA phosphorylation between these two diseases (P<.05).

Review article: treatment of Helicobacter pylori infection and factors influencing eradication

Currently available Helicobacter pylori eradication therapies are considered very effective and safe. The most recent eradication guidelines proposed in the Maastricht 2-2000 Consensus Report recommend the use of proton pump inhibitors (standard b.d.) along with clarithromycin (500 mg b.d.) and amoxycillin (1000 mg b.d.) or metronidazole (500 mg b.d.) for a minimum of 7 days. The combination of amoxycillin and clarithromycin is preferred because it may favour best results with a second-line proton pump inhibitor quadruple therapy. The recommended second-line therapy includes a combination of a proton pump inhibitor (standard b.d.) with bismuth salt (subsalicylate/subcitrate 120 mg q.d.s.), metronidazole (500 mg t.d.s.), and tetracycline (500 mg q.d.s.) for a minimum of 7 days. Extended proton pump inhibitor-based triple therapy can be used if bismuth is not available. Specialists should manage subsequent failures. Based on direct and indirect evidence from well-designed studies and clinical experience, eradication is recommended in gastric and duodenal ulcers, MALToma, atrophic gastritis, postgastric cancer resection, and in first-degree relatives of gastric cancer patients. The most common reason for treatment failure is poor compliance with eradication guidelines. Antibiotic resistance may be a significant factor in certain geographical areas. Proton pump inhibitors are an integral part of the eradication regimens as proved by meta-analyses of clinical trials. Novel agents used in secondary failure are few and depend on the use of new antibiotics. The role of H. pylori-specific antibiotics, probiotics, and vaccines is not established as yet. Widespread acceptance of the eradication guidelines should be regarded as the single most important factor in eradication success.