Helicobacter pylori vacA d1 genotype is associated with gastric cancer but not peptic ulcers in Kurdistan region, northern Iraq.

We read with interest the paper by Basiri and colleagues studying the prevalence of vacA d1 and d2 genotypes in the H pylori isolates from patients with gastric adenocarcinoma, peptic ulcer disease and gastritis in East Azerbaijan region, where the incidence of gastric cancer (GC) is high. They found that 43.4% of the isolate carried the d1 allele and 56.6% carried subtype d2. A significant correlation between vacA d1 and gastric adenocarcinoma or PUD was shown. The study suggested that the H pylori vacA d1 genotype helps predict risk for gastric adenocarcinoma and PUD in East Azerbaijan, Iran (Basiri et al., 2014). Despite the geographical proximity of Iraq and Iran the incidence of gastric cancer differs hugely between these countries; in Iran it ranges from 38-69/105 compared to 5/105 in Iraq (GLOBOCAN, 2002; Sadjadi et al., 2005; Yavari et al., 2006). Previous studies of H. pylori virulence factors were not successful in the explanation of such a difference in cancer rate. We hypothesised that H pylori vacA d1 may help understanding this variation in cancer rate in these two neighbouring countries. DNA was extracted from 157 H. pylori strains isolated from patients with different clinical outcome (non-ulcer disease (NUD): 81; gastric ulcer (GU): 31; duodenal ulcer (DU):38 and gastric cancer:5). Using the same methodology mentioned in the Basiri et al paper, we typed these strains for vacA d subtypes. Overall, (45/157) 28.6% of our samples typed as vacA d1 and (112/157) 71.4% as vacA d2. It was found that (21/81) 26% of the strains isolated from NUD typed as vacA d1. In addition, vacAd1 genotype was found in (9/38) 23.6% and (10/31) 30.3% of DU and GU samples, respectively. Interestingly, all the isolates obtained from GC patients were vacAd1. No association was found between vacA d genotypes and DU and GU (Chi square test; p>0.05). However, a statistical significant relationship was found between vacA d1 and gastric cancer (Exact Fischer test; p=0.002). H. pylori strains possessing cagA are associated with a significantly increased risk for the development of atrophic gastritis, peptic ulcer disease (PUD) and gastric cancer (Atherton, 2006). Previous study comparing H. pylori strains from these two countries showed that no difference in prevalence of cagA+ strains between unselected dyspeptic populations from these countries (Hussein et LETTER to the EDITOR