One-step polymerase chain reaction-based typing of Helicobacter pylori vacA gene:: association with gastric histopathology

Heterogeneity of the Helicobacter pylori vacA gene may be associated with bacterial virulence and presentation. In this study, the possible correlation between vacA genotypes and gastric histopathology was investigated. Using a modified one-step polymerase chain reaction (PCR)-based method, 122 of 131 H. pylori isolates obtained from 63 of 67 patients from Germany were classified into distinct vacA genotypes according to their signal sequence (s1 or s2) and their midregion alleles (m1 or m2). A possible subtype of mi, now alluded to as m3, was identified in one-third of the isolates. Signal sequence sl was significantly associated with higher H. pylori density but not with gastric inflammation parameters as compared with s2. Compared with m2, mi initially appeared to correlate with higher mononuclear cell scores in corpus, although not with H. pylori density. Upon differentiation between mi and m3, however, only the latter was associated with the high cell scores. Moreover, m3 also correlated with a higher antral H. pylori density. Positive cagA status correlated significantly with vacA signal sequence sl, and higher gastric mononuclear cell scores and corpus neutrophil score. H. pylori density was always associated with enhanced gastric neutrophil and corpus mononuclear cell scores. These data indicate a significant association of specific vacA genotypes with enhanced bacterial density and gastric inflammation. PCR-based identification of the respective alleles can now easily be performed in the diagnostic laboratory using a one-step PCR assay.