[Molecular detection of Helicobacter pylori vacA and cagA genes in gastric tissue specimens of patients with peptic ulcer disease and non-ulcer dyspepsia].Mikrobiyol Bul. 2011 Jan; 45(1):11-20.MB
Helicobacter pylori can colonize the gastric mucosa and is considered as a risk factor for chronic active gastritis, peptic ulcer, gastric adenocarcinoma and primary gastric lymphoma. Among its various virulence factors, vacuolating cytotoxin encoded by vacA and cytotoxin-associated toxin encoded by cagA gene play an important role. The aims of this study were the detection of H.pylori vacA s and m genotypes, investigation of the association between vacA genotypes and cagA gene presence, and evaluation of the correlation between those factors and the clinical diagnosis. Gastric tissue specimens of patients who were clinically diagnosed as peptic ulcer disease (PUD) and non-ulcer dyspepsia (NUD) were included in the study. A total of 29 patients (age range: 18-74 years, mean age: 47.8 ± 13.6 years; 19 were female) without any familial relationship were evaluated. Thirteen (44.8%) of the patients were diagnosed clinically as PUD, while 16 (55.2%) as NUD. All of the patients' gastric tissue samples obtained by endoscopy were urease positive. H.pylori DNA was extracted from the tissue specimens by proteinase-K, phenol-chloroform-isoamyl alcohol method and vacA s, m1, m2 and cagA regions were identified by polymerase chain reaction (PCR) using four different primer sets. In addition, DNA sequencing was performed for the protected 785 base-pairs region of vacA m gene in all of the samples, and the sequences were aligned with Gene-Bank sequences, creating a phylogenetic tree. The distribution of vacA genotypes between 29 H.pylori positive patients were found as; s1m1 (n= 16), s1m2 (n= 6) and s2m2 (n= 7), while 19 patients yielded positive results for cagA gene. CagA positivity was detected in all of the 16 patients harboring s1m1 genotype, and 13 of those were the patients diagnosed as PUD (p= 0.008). Genotyping data achieved by phylogenetic analysis of the vacA m region were compatible with m genotypes identified by PCR. In conclusion, we detected a significant relationship between PUD and vacA s1m1 and cagA positivity. It was also determined that PCR would be a reliable, simpler and cheaper alternative to nucleotide sequencing for the identification of H.pylori vacA m genotypes.