Analysis of the 3' Variable Region of Cytotoxin-Associated Gene A (<i>cagA</i>) in <i>Helicobacter pylori</i>Isolates in China

Infection by the bacterium Helicobacter pylori is a putative cause of various gastric disorders, including gastric adenocarcinoma. Incident rates are associated with variants of the H. pylori virulence factor cytotoxin-associated gene A protein (CagA), encoded by the gene cagA. However, these variants have not been characterized in China, where gastric cancer is common. We investigated the diversity of CagA variants in H. pylori strains isolated from a Chinese population. The 3' variable region of cagA genes from 66 clinical isolates in China were amplified by polymerase chain reaction, sequenced, aligned, and analyzed. All 66 H. pylori strains were CagA-positive, of which 93.9% were East Asian type and the tyrosine phosphorylation motifs (TPMs) were EPIYA-ABD. The remainder was Western type, in which TPMs were EPIYA-ABC. Interestingly, two of sixty-two strains (3.2%) of the East Asian type were mutated into ESIYA-B, whereas all four Western type (100%) strains were mutated into EPIYT-B. Both of the two strains with Western-type CagA obtained from gastric cancer patients contained a distinguished mutation on the first residue following the EPIYA site in the EPIYA-A motif. The predominant CagA type in these H. pylori strains isolated from Chinese patients in China was East Asian, with TPMs EPIYA-ABD, and there existed mutations in both the East Asian and Western type CagA.

Effect of treatment failure on the Cag A EPIYA motif in Helicobacter pylori strains from Colombian subjects

AIM To evaluate effect of treatment failure on cag A and vac A genotypes in Helicobacter pylori(H. pylori) isolates from Colombia.METHODS One hundred and seventy-six participants infected with H. pylori from Colombia were treated during 14 d with the triple-standard therapy. Six weeks later, eradication was evaluated by 13C-Urea breath test. Patients with treatment failure were subjected to endoscopy control; biopsies obtained were used for histopathology and culture. DNA from H. pylori isolates was amplified using primers specific for cag A and vac A genes. The phylogenetic relationships among isolates obtained before and after treatment were established by conglomerate analysis based on random amplified polymorphic DNA(RAPD) fingerprinting.RESULTS Treatment effectiveness was at 74.6%. Of the par-ticipants with treatment failure, 25 accepted subjected to a second endoscopy. Prevalence of posttreatment infection was 64%(16/25) and 40%(10/25) by histology and culture, respectively. Upon comparing the cag A and vac A genotypes found before and after therapy, multiple cag A genotypes(cag A-positive and cag A-negative) were found before treatment; in contrast, cag A-negative genotypes decreased after treatment. vac A s1m1 genotype was highly prevalent in patients before and after therapy. The 3'cag A region was successfully amplified in 95.5%(21/22) of the isolates obtained before and in 81.8%(18/22) of the isolates obtained after treatment. In the isolates obtained from patients with treatment failure, it was found that 72.7%(16/22) presented alterations in the number of EPIYA motifs, compared to isolates found before treatment.CONCLUSION Unsuccessful treatment limits colonization by lowvirulence strains resulting in partial and selective eradication in mixed infections, and acts on the cag A-positive strains inducing genetic rearrangements in cag A variable region that produces a loss or gain of EPIYA repetitions.