Quasispecies development of Helicobacter pylori observed in paired isolates obtained years apart from the same host

Helicobacter pylori isolates show greater genetic diversity than other bact erial species studied, but the basis for this phenomenon is unknown. Whethe r detectable genomic mutation appears within an H. pylori population during persistent colonization was investigated, Paired H, pylori populations obt ained across 7- to 10-year intervals from 13 patients were characterized by use of methods including polymerase chain reaction (PCR) genotyping for ca gA, vacA, iceA, recA, and IS605; random arbitrarily primed DNA (RAPD)-PCR a nd amplified fragment length polymorphism (AFLP) analysis; and ELISA, to de termine Lewis phenotypes, Genotyping, including recA sequence analysis, rev ealed that initial and follow-up populations represented the same populatio n in 11 patients (85%). Nevertheless, distinct dissimilarities were shown w ithin each of these 11 pairs by both RAPD-PCR and AFLP analyses, During fol low-up, Lewis-y levels, but not Lewis-x levels, decreased significantly. Th e changes detected by RAPD-PCR and AFLP indicate that genetic drift occurs within H. pylori populations over the course of years of colonization of a single host.