Helicobacter pylori genotypes in Russia.

Abstract

Numerous studies have indicated that Helicobacter pylori is one of the most frequent pathogens, affecting up to 50% of the human population worldwide [1, 2, 3]. While the majority of infected people have no clinical manifestation, they nevertheless constitute a risk group for subsequent development of chronic gastritis, gastric ulcer, duodenal ulcer, extranodal B-cell MALT lymphoma or gastric adenocarcinoma. There is evidence that genetic variability of Helicobacter pylori is related to the risk of disease. Several genes of Helicobacter pylori, such as cagA, vacA, iceA and babA are considered to be associated with virulence. Clinical isolates of Helicobacter pylori may vary markedly with geographic location, and studies on the incidence and distribution of pathogenicity markers of the bacterium may shed light on their significance and versatility. Much work has been done on genotyping Helicobacter pylori all over the world [4]. Yet, clinical isolates obtained in Russia (which occupies as much as about 1/6th of the world’s land mass) have not been genotyped so far. In the study presented here, we investigated the prevalence of the cagA, vacA, iceA and babA genes and the subtyping of vacA in Helicobacter pylori isolates recovered from patients with duodenal ulcers and chronic gastritis in Russia. A total of 42 Helicobacter pylori isolates obtained from patients in different locations throughout Russia (central region, 20; Siberia, 5; Volga region, 11; and northwestern region, 6) were used. Helicobacter pylori isolates were obtained from the antrum and the corpus of patients with histologically confirmed duodenal ulcer (n=20) and chronic gastritis (n=22). Patients (23 male, 19 female) were age matched, with a median age of 45 years (range, 19–62 years). Three of the patients were Mongolian and 39 were mixed European. Patients receiving antisecretory therapy or nonsteroidal anti-inflammatory drugs were excluded. All biopsies were collected at the Institute of PhysicoChemical Medicine, Moscow, Russia. Chromosomal DNA was extracted from 72-h plate cultures of each strain using the Helicopol Isolation Kit (Lytech, Russia) in accordance with the manufacturer’s recommendations. For each isolate, cagA, vacA, iceA and babA genotypes were characterized by PCR as described previously [5, 6, 7, 8]. Genotypes were successfully and fully determined for all isolates, and the results are given in Table 1. Of the 42 isolates examined, 39 were positive for the cagA gene. The iceA2 gene was not found independently in clinical isolates. It was found only in combination with iceA1 in 10 of the 42 isolates. The iceA1 gene alone was detected in 26 Helicobacter pylori isolates. The babA2 gene was verified in 31 isolates. The vacA genotypes were identified in all 42 Helicobacter pylori isolates. The vacAs1 genotype was found in 31 of the 42 clinical isolates. Seven Helicobacter pylori strains verified in clinical isolates had the vacAs2 genotype. No samples with the vacAs2/m1 genotype were found. Interestingly, mixed vacA genotypes (s1/s2 or m1/m2), indicative of more than one strain variant of Helicobacter pylori, were found in 15 of the 42 clinical isolates. Certain combinations of the vacAs1, cagA, iceA1 and babA2 were revealed. The type 1 gene combination (vacAs1, cagA and babA2) was found in 57.1% of the clinical isolates and the type 2 combination (vacAs1, cagA, iceA1 and babA2) was found in 45.2%. No association was found between the babA2-positive genotype and vacAs1, cagA or iceA1 genotypes in the clinical isolates of Helicobacter pylori (P>0.2 in all cases). Therefore, we investigated the presence of cagA, vacA, iceA1 and babA2 genes in clinical Helicobacter pylori isolates and correlated these data with the presence of gastritis and duodenal ulcer. K. Momynaliev ()) · V. Govorun Department of Gene Engineering and Immunogenetics, Institute of Physico-Chemical Medicine, Russian Federation Ministry of Public Health, Malaya Pirogovskaya Street 1A, Moscow 119992, Russia e-mail: dhoroshun@nm.ru Tel.: +7-095-2454236 Fax: +7-095-2464501