Helicobacter pylori isolates from different patients are characterized
By diversity in the nucleotide sequences of individual genes, variati
on in genome size, and variation in gene order, Genetic diversity is p
articularly striking in vacuolating cytotoxin (vacA) alleles, In this
study, five open reading frames (ORFs) were identified within a 4,2-kb
region downstream from vacA in H. pylori 60190, One of these ORFs was
closely related to the virulence-associated protein D (vapD) gene of
Dichelobacter nodosus (64.9% nucleotide identity), A probe derived fro
m vapD of H. pylori 60190 hybridized with only 19 (61.3%) of 31 H. pyl
ori strains tested, Sequence analysis of the vapD region in vapD-negat
ive H. pylori strains revealed that there were two different families
of similar to 0.5-kb DNA segments, which were both unrelated to vapD.
The presence of vapD was not associated with any specific family of va
cA alleles, These findings are consistent with a recombinational popul
ation structure for H. pylori.