Allelic variation in theHelicobacter pyloriflagellin genesflaA andflaB: its consequences for strain typing schemes and population structure

Abstract

Summary: Extensive DNA sequence diversity was noted inHelicobacter pyloriflagellin genesflaA andflaB. PCR amplified sequences from 49 isolates were digested withAluI.HindIII.MboI orMspI, the resultant patterns were compared between the different isolates and these used to differentiate the isolates from each other. Evidence that the extensive diversity that was found in these genes is the result of reassortment of sequences between strains in the bacterial population is presented, such that a comparatively small number of individual sequence mutations can recombine together in random combinations to form a greater number of distinct alleles. Geographical differences in the predominant patterns in theflaA alleles were also observed and could reflect regional differences either in the human host population or in the bacterial population. In view of the genetic complexity of this species, molecular typing schemes designed to identify related strains may falsely associate strains if the methods do not characterize sufficient genetic sites to exclude chance associations of genetic markers in strains which are actually not closely related to each other.