EVIDENCE FOR RECOMBINATION IN THE FLAGELLIN LOCUS OF CAMPYLOBACTER-JEJUNI - IMPLICATIONS FOR THE FLAGELLIN GENE TYPING SCHEME

The flagellin subunit of the flagellar filament in Campylobacter jejun i is encoded bq two highly homologous tandem genes, flaA and flaB. The flaA gene was sequenced in 18 strains of C. jejuni, including isolate s from three outbreak groups. Sequences obtained were compared with fl aA sequences available in the GenBank database, and all were analyzed for mosaic gene structure by using recently described statistical test s fur detecting gene conversion among aligned sets of sequences. Stron g evidence was found supporting recombination between flaA genes of di fferent strains (i.e., intergenomic recombination), Intragenomic recom bination between the flaA and flaB genes of C. jejuni TGH9011 was also demonstrated, Both mechanisms Of recombination may act as a potential means by which pathogenic strains can generate increased antigenic di versity, so allowing them to escape the immunological responses of the host, Furthermore, demonstration of recombination within and between flagellin loci of natural strains suggests that flagellin gene typing (restriction fragment length polymorphism analysis of PCR-amplified fl agellin genes) cannot be considered a stable method for long-term moni toring of pathogenic Campylobacter populations.