Helicobacter pylori: detection of iceA1 and iceA2 genes in the same strain in Mexican isolates

Helicobacter pylori iceA1 and iceA2 gene amplification is usually performed to identify mixed populations as both genes are apparently reportedly exclusive. However, some strains isolated from Mexico show both iceA genes. The aim of this study was to establish the frequency of these genes in Mexican isolates and genomic diversity of the H. pylori strains.

One hundred thirty six biopsies were obtained from 68 patients (39 children and 29 adults). The presence of H. pylori was confirmed in 3/18 children and 6/19 adults by culture. There were 93 clinical strains isolated from nine patients. Additionally, we studied 37 strains from a strain collection isolated from 10 patients. The strains were genotyped and dual iceA genes were identified by polymerase chain reaction (PCR) and amplicons were sequenced. In addition, an enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) assay was performed as fingerprinting method.

The genotypification of the H. pylori isolates indicated that all strains were vacA+; 86% babA2+, 86% cagA+, 82% vacA s1m1+, 19% iceA1+, 9% iceA2+, and 72% of them carried both iceA1 and iceA2 genes. The ERIC-PCR profiling revealed that the strains clustered in eight genetic groups depending on the presence of iceA1, iceA2 or both. A basic local multiple alignment analysis of the nucleotide sequences revealed that the iceA1 and iceA2 genes exhibited no relevant similarity.

The results here showed the presence of triple-positive strains (babA, cagA, vacA) of H. pylori and strains carrying simultaneously both iceA1 and iceA2 genes.