[Helicobacter pylori: cagA analysis and vacA genotyping in Chile. Detection of a s2/m1 strain]

The genes cagA and vacA encode H pylori virulence factors.

To genotype these genes in H pylori strains isolated from patients with upper gastrointestinal symptoms.

We studied 50 patients who underwent an upper gastrointestinal endoscopy, with positive culture for H pylori. Detection of cagA and vacA genotyping was done using polymerase chain reactions.

The gene cagA was detected in 19 samples (38%). Signal sequences s1 and s2 of vacA gene were detected in 16 samples each (32%). There was simultaneous amplification of s1 and s2 in 6 samples and they were not detected in 9 samples. The middle region of vacA was m1 in 9 samples, m2 in 29 samples and there was simultaneous amplification of m1 and m2 in 12 samples. In 16 samples (32%), more than one type of signal sequence or medial region was detected. Of those patients in whom vacA was the only genotype detected, 15 were s2/m2, 7 were s1/m1, 4 were s1/m2 and 1 was s2/m1.

In these patients, the infection with cagA- H pylori strains, predominates, the prevalence of infection with s1 or s2 strains is similar and the predominant medial region is m2.