Serum Helicobacter pylori antibody reactivity in seven Asian countries using an automated latex aggregation turbidity assay

BACKGROUND AND AIM

To determine the application range of diagnostic kits utilizing anti-Helicobacter pylori antibody, we tested a newly developed latex aggregation turbidity assay (latex) and a conventional enzyme-linked immunosorbent assay (E-plate), both containing Japanese H. pylori protein lysates as antigens, using sera from seven Asian countries.

METHODS

Serum samples (1797) were obtained, and standard H. pylori infection status and atrophy status were determined by culture and histology (immunohistochemistry) using gastric biopsy samples from the same individuals. The two tests (enzyme-linked immunosorbent assay and latex) were applied, and receiver operating characteristics analysis was performed.

RESULTS

Area under the curve (AUC) from the receiver operating characteristic of E-plate and latex curves were almost the same and the highest in Vietnam. The latex AUC was slightly lower than the E-plate AUC in other countries, and the difference became statistically significant in Myanmar and then Bangladesh as the lowest. To consider past infection cases, atrophy was additionally evaluated. Most of the AUCs decreased using this atrophy-evaluated status; however, the difference between the two kits was not significant in each country, but the latex AUC was better using all samples. Practical cut-off values were 3.0 U/mL in the E-test and 3.5 U/mL in the latex test, to avoid missing gastric cancer patients to the greatest extent possible.

CONCLUSIONS

The kits were applicable in all countries, but new kits using regional H. pylori strains are recommended for Myanmar and Bangladesh. Use of a cut-off value lower than the best cut-off value is essential for screening gastric cancer patients.

Population-based study of Helicobacter pylori infection and antibiotic resistance in Bhutan

OBJECTIVES

Bhutan suffers from a high prevalence of Helicobacter pylori (H. pylori) infection and gastric cancer-related mortality. In preparation for a countrywide H. pylori eradication program, the antibiotic resistance patterns of H. pylori infection were surveyed in different geographical regions.

METHODS

Dyspeptic patients in 6 districts including Thimphu, Punakha, Wangdue, Trongsa, Bumthang, and Haa underwent upper gastrointestinal endoscopy during GASTROCAMP and were enrolled between December 2010 and April 2015. Gastric biopsies were obtained for rapid urease test, histopathology, and H. pylori culture. Antimicrobial susceptibility testing was later performed if the culture was positive.

RESULTS

A total of 1178 patients were surveyed. The overall H. pylori infection in Bhutan was 66.2%. Punakha had the highest prevalence of H. pylori infection (85.6%). Thimphu and Punakha (city areas) had higher prevalence of H. pylori infection than rural districts (73.5% vs 63.3%, OR=1.61, 95% CI 1.22-2.13, p=0.0008). There were 357 patients (30.3%) with positive H. pylori culture completed antimicrobial susceptibility testing. The mean age was 40.5 years with female predominance (57.1%). No amoxicillin resistant strains were found. Metronidazole resistance was 81% followed by levofloxacin resistance (8.1%). Clarithromycin (2%) and tetracycline (0.6%) resistance was rare except in Thimphu, the capital city (10%) vs 0% in rural areas, p<0.001. The metronidazole resistance rate remained stable at approximately 80% during the past 5 years of study. Levofloxacin-resistant strains gradually rose from 5.3% in 2010 to 9.9% in 2015.

CONCLUSIONS

Bhutan had a high prevalence of H. pylori infection. Metronidazole resistance was extremely high, whereas clarithromycin resistance was quite low in this specific area. Antibiotic resistance pattern could be good evidence for guiding a proper treatment regimen for H. pylori infection in Bhutan.

Efficacy of Omeprazole, Tetracycline, and 4 Times Daily Dosing of Amoxicillin in Helicobacter pylori Eradication in Limited Resource Area in Bhutan: A Prospective Randomized Trial (BHUTAN Study)

Backgrourd:

H. pylori-associated gastric cancer is the first cancer-related death in Bhutan. Effective regimen for H. pylori eradication is essential to reduce risk of developing gastric cancer. Clarithromycin is not widely used in this limited resource country. Aim of this study was to evaluate proper regimen and prevalence of antibiotic resistance pattern for H. pylori eradication in Bhutan.

Methods:

Five hundred and forty-six patients underwent gastroscopy during GASTROCAMP between October 2014 and April 2015 in Bhutan and 77 patients were enrolled. Four gastric biopsies were obtained for rapid urease test, histopathology, H. pylori culture with Epsilometer test. All H. pylori-positive patients were randomized to receive either 7-day or 14-day of 500 mg amoxicillin four times daily, 500 mg tetracycline four times daily, and 20 mg omeprazole twice daily.

Results:

Seventy-seven subjects were enrolled (54 females, 23 males, mean age = 45.4 years). Of 77 patients, 52 (67.5%) received 7-day regimen while 25 (32.5%) had 14-day regimen. Prevalence of H. pylori was 38.2%. Antibiotic resistance was 80.0% for metronidazole, 11.1% for levofloxacin and no resistance seen in amoxicillin, tetracycline and clarithromycin. Overall eradication rates of 7-day and 14-day regimens were 51.9% and 80.0%, p = 0.02. Female and age ≥40 years had significantly higher eradication rate when receiving 14-day compared to 7-day regimen (94.1% vs. 45.9%, OR = 18.82; 95% CI 2.26-157.02, p = 0.0007 and 86.7% vs. 50.0%, OR = 6.50; 95% CI 1.25-33.91, p = 0.02, respectively).

Conclusions:

Fourteen-day regimen might be an acceptable regimen for H. pylori eradication in limited resource area such as Bhutan. Female and age ≥40 years should receive longer duration of treatment. This 14-day regimen could at least reduce the risk of developing H. pylori-associated diseases especially peptic ulcer with complications and gastric cancer which lead to many deaths in Bhutan.

Characterization of a novel Helicobacter pylori East Asian-type CagA ELISA for detecting patients infected with various cagA genotypes

Currently, Western-type CagA is used in most commercial Helicobacter pylori CagA ELISA kits for CagA detection rather than East Asian-type CagA. We evaluated the ability of the East Asian-type CagA ELISA developed by our group to detect anti-CagA antibody in patients infected with different cagA genotypes of H. pylori from four different countries in South Asia and Southeast Asia. The recombinant CagA protein was expressed and later purified using GST-tag affinity chromatography. The East Asian-type CagA-immobilized ELISA was used to measure the levels of anti-CagA antibody in 750 serum samples from Bhutan, Indonesia, Myanmar, and Bangladesh. The cutoff value of the serum antibody in each country was determined via Receiver-Operating Characteristic (ROC) analysis. The cutoff values were different among the four countries studied (Bhutan, 18.16 U/mL; Indonesia, 6.01 U/mL; Myanmar, 10.57 U/mL; and Bangladesh, 6.19 U/mL). Our ELISA had better sensitivity, specificity, and accuracy of anti-CagA antibody detection in subjects predominantly infected with East Asian-type CagA H. pylori (Bhutan and Indonesia) than in those infected with Western-type CagA H. pylori predominant (Myanmar and Bangladesh). We found positive correlations between the anti-CagA antibody and antral monocyte infiltration in subjects from all four countries. There was no significant association between bacterial density and the anti-CagA antibody in the antrum or the corpus. The East Asian-type CagA ELISA had improved detection of the anti-CagA antibody in subjects infected with East Asian-type CagA H. pylori. The East Asian-type CagA ELISA should, therefore, be used in populations predominantly infected with East Asian-type CagA.

Helicobacter pylori bab characterization in clinical isolates from Bhutan, Myanmar, Nepal and Bangladesh

BACKGROUND

Helicobacter pylori BabA is an important outer membrane protein that involves in the attachment to the gastric mucosa and enhances the virulence property of the bacterium. This study was aimed to characterize the bab genotypes, to evaluate its association with cagA, vacA and clinical diseases as well as degree of gastric inflammation.

METHODS

H. pylori isolates from four countries were subjected for the characterization of bab. The locus specific forward and bab specific reverse primers were used to get the specific products by PCR, which could distinguish the three locus (A, B and C). The histological activities were evaluated according to the Updated Sydney system.

RESULT

In patients from high risk countries (Bhutan and Myanmar) relatively higher frequencies of strains with babA-positivity (91.8% and 90.7%, respectively), babA at locus A (98% and 91.2%, respectively) and with single babA (96.8% and 91.2%, respectively) were found. Strains with two loci occupied were the most prevalent in Bhutan (84.6%), Myanmar (74.7%), Nepal (58.3%) and Bangladesh (56.9%). The genotype babA at locus A/babB at locus B/bab-negative at locus C (babA/babB/-) was the most common genotype isolated from Bhutan (82.7%), Myanmar (58.7%), Nepal (32%) and Bangladesh (31.4%) among all genotypes assessed. This genotype was also associated with the peptic ulcer disease (P = 0.013) when compared to gastritis. babA-positive characteristics and the genotype babA/babB/- exhibited the enhanced histological activities.

CONCLUSIONS

The higher prevalence of virulence associated babA-positive characteristics and enhanced histological activities in Bhutan than in Myanmar, Nepal and Bangladesh might partly explain why the peoples in Bhutan are at higher risk for developing severe gastric complications.

Differences in interleukin 8 expression in Helicobacter pylori-infected gastric mucosa tissues from patients in Bhutan and the Dominican Republic

The outcomes of Helicobacter pylori infection vary geographically. H pylori strains, disease presentation, and environments differ markedly in Bhutan and Dominican Republic. The aims were to compare the strains, histology, and expression of interleukin (IL) 8 and IL-10 from gastric mucosa from the 2 countries. H pylori status was assessed by the combination of rapid urease test, culture, and histology. Histology was evaluated using the updated Sydney System, and cytokines in gastric biopsies were measured using real-time polymerase chain reaction (PCR). There were 138 subjects from Bhutan and 155 from Dominican Republic. The prevalence of H pylori infection was 65% and 59%, respectively. The genotype of cagA was predominantly East Asian type in Bhutan versus Western type in Dominican Republic. Gastritis severity was significantly higher in H pylori-infected subjects from Bhutan than those from Dominican Republic. IL-8 expression by H pylori infection was 5.5-fold increased in Bhutan versus 3-fold in Dominican Republic (P < .001); IL-10 expression was similar. IL-8 expression levels among H pylori-infected cases tended to be positively correlated with polymorphonuclear leucocyte and monocyte infiltration scores in both countries. IL-8 expression among those with grade 2 and 3 polymorphonuclear leucocyte and monocyte infiltration was significantly higher in Bhutan than in Dominican Republic. The difference in IL-8 expression in the 2 countries is reflected in the different disease pattern between them. Whether the dominant factor is differences in H pylori virulence, in host-H pylori-environmental interactions, genetic factors or all remains unclear. However, severity of inflammation appears to be a critical factor in disease pathogenesis. We compared IL-8 messenger RNA levels between the high gastric cancer risk country, Bhutan (mainly East Asian-type H pylori), and the lower gastric cancer risk country, Dominican Republic (mainly Western-type H pylori).

Antibiotics resistance rate of Helicobacter pylori in Bhutan

AIM: To survey the antibiotic resistance pattern of Helicobacter pylori (H. pylori) strains isolated from Bhutanese population.

METHODS: We isolated 111 H. pylori strains from the gastric mucosa of H. pylori-infected patients in Bhutan in 2010. The Epsilometer test was used to determine the minimum inhibitory concentrations (MICs) of amoxicillin (AMX), clarithromycin (CLR), metronidazole (MNZ), levofloxacin (LVX), ciprofloxacin (CIP), and tetracycline (TET).

RESULTS: Nineteen of the isolated H. pylori strains were susceptible to all antibiotics tested. The isolated strains showed the highest rate of antibiotic resistance to MNZ (92/111, 82.9%). Among the 92 MNZ-resistant strains, 74 strains (80.4%) showed high-level resistance (MIC ≥ 256 μg/mL). Three strains were resistance to LVX (2.7%). These strains were also resistance to CIP. None of the strains showed resistance to CLR, AMX and TET.

CONCLUSION: CLR-based triple therapy is a more effective treatment approach over MNZ-based triple therapy for H. pylori infection in Bhutan.

Seroprevalence of Helicobacter pylori infection and gastric mucosal atrophy in Bhutan, a country with a high prevalence of gastric cancer

Gastric cancer is the second leading cause of cancer-related mortality in the world. Recently, serum Helicobacter pylori antibodies and pepsinogen (PG) have been used for gastric cancer screening. The incidence of gastric cancer in Bhutan is reported to be quite high compared with that in neighbouring countries. In this study, 381 subjects from three areas of Bhutan were assessed for gastric mucosal atrophy and serological parameters. Anti-H. pylori IgG, PG I, PG II and cytotoxin-associated gene A (CagA) antibodies were measured using ELISA. Subjects were classified into four groups according to H. pylori and PG seropositivity: Group A (H. pylori-negative/PG-negative), Group B (H. pylori-positive/PG-negative), Group C (H. pylori-positive/PG-positive) and Group D (H. pylori-negative/PG-positive). The prevalence of H. pylori in the 381 subjects was 71.1% (271/381), with high infection rates found in rural areas. The PG I/II ratio was significantly inversely correlated with the atrophy score in the antrum and the corpus (P<0.001). Multivariate analysis showed that the PG status was significantly associated with the presence of atrophy in the corpus. The prevalence of the PG-positive status was significantly higher among H. pylori-positive subjects than among H. pylori-negative subjects (P<0.001). Based on the ABC method, Group B was the most dominant, followed by Group A, Group C and Group D. The high incidence of gastric cancer in Bhutan can be attributed to the high prevalence of H. pylori infection and gastric mucosal atrophy.

Extremely high prevalence of Helicobacter pylori infection in Bhutan

AIM: To revealed the prevalence of Helicobacter pylori (H. pylori) infection in the Bhutanese population.

METHODS: We recruited a total of 372 volunteers (214 females and 158 males; mean age of 39.6 ± 14.9 years) from three Bhutanese cities (Thimphu, Punaka, and Wangdue). The status of H. pylori infection was determined based on five different tests: the rapid urease test (CLO test), culture, histology, immunohistochemistry (IHC), and serum anti H. pylori-antibody.

RESULTS: The serological test showed a significantly higher positive rate compared with the CLO test, culture, histology and IHC (P < 0.001, P < 0.001, P = 0.01, and P = 0.01, respectively). When the subjects were considered to be H. pylori positive in the case of at least one test showing a positive result, the overall prevalence of H. pylori infection in Bhutan was 73.4%. The prevalence of H. pylori infection significantly decreased with age (P < 0.01). The prevalence of H. pylori infection was lower in Thimphu than in Punakha and Wangdue (P = 0.001 and 0.06, respectively). The prevalence of H. pylori infection was significantly higher in patients with peptic ulcers than in those with gastritis (91.4% vs 71.3%, P = 0.003).

CONCLUSION: The high incidence of gastric cancer in Bhutan may be attributed to the high prevalence of H. pylori infection.