Abstract
BackgroundThe cagA gene is one of the important virulence factors of Helicobacter pylori. The diversity of cagA 5′ conserved region is thought to reflect the phylogenetic relationships between different H. pylori isolates and their association with peptic ulceration. Significant geographical differences among isolates have been reported. The aim of this study is to compare Turkish H. pylori isolates with isolates from different geographical locations and to correlate the association with peptic ulceration.MethodsTotal of 52 isolates of which 19 were Turkish and 33 from other geographic locations were studied. Gastric antral biopsies collected from 19 Turkish patients (Gastritis = 12, ulcer = 7) were used to amplify the cagA 5′ region by PCR then followed by DNA sequencing.ResultsThe phylogenetic tree displayed 3 groups: A) a mix of 2 sub-groups “Asian” and “African/Anatolian/Asian/European”, B) “Anatolian/European” and C) “American-Indian”. Turkish H. pylori isolates clustered in the mixed sub-group A were mostly from gastritis patients while those clustered in group B were from peptic ulcer patients. A phylogenetic tree constructed for our Turkish isolates detected distinctive features among those from gastritis and ulcer patients. We have found that 2/3 of the gastritis isolates were clustered alone while 1/3 was clustered together with the ulcer isolates. Several amino acids were found to be shared between the later groups but not with the first group of gastritis.ConclusionsThis study provided an additional insight into the profile of our cagA gene which implies a relationship in geographic locations of the isolates.
Highlights
The cagA gene is one of the important virulence factors of Helicobacter pylori
Several studies showed that cagA-positive H. pylori strains are more often isolated from patients with gastric ulcers (GU), duodenal ulcers (DU) and gastric cancer (GC) than those with gastritis (G) [3,4]
In a previous study it has been shown that there is less than 53% homology between the CagA repeat sequences of Western and East Asian strains indicating the existence of gene variability that might affect the toxin strength [8]
Summary
The cagA gene is one of the important virulence factors of Helicobacter pylori. The diversity of cagA 5′ conserved region is thought to reflect the phylogenetic relationships between different H. pylori isolates and their association with peptic ulceration. The aim of this study is to compare Turkish H. pylori isolates with isolates from different geographical locations and to correlate the association with peptic ulceration. The variation in the size of the CagA protein has been correlated with the varying number of repeat sequences located in the 3′ variable region of the gene that encodes the EPIYA motifs [7]. In a previous study it has been shown that there is less than 53% homology between the CagA repeat sequences of Western and East Asian strains indicating the existence of gene variability that might affect the toxin strength [8]
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