Evidence for recombination in the flagellin locus of Campylobacter jejuni: implications for the flagellin gene typing scheme

Abstract

The flagellin subunit of the flagellar filament in Campylobacter jejuni is encoded by two highly homologous tandem genes, flaA and flaB. The flaA gene was sequenced in 18 strains of C. jejuni, including isolates from three outbreak groups. Sequences obtained were compared with flaA sequences available in the GenBank database, and all were analyzed for mosaic gene structure by using recently described statistical tests for detecting gene conversion among aligned sets of sequences. Strong evidence was found supporting recombination between flaA genes of different strains (i.e., intergenomic recombination). Intragenomic recombination 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 diversity, 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 flagellin genes) cannot be considered a stable method for long-term monitoring of pathogenic Campylobacter populations.

Bacteriophage influence Campylobacter jejuni types populating broiler chickens

“…Inter-genomic recombination in Campylobacter has been suggested as a role of generating genome diversity (Harrington et al, 1997;Dingle et al, 2001;Suerbaum et al, 2001;de Boer et al, 2002;Schouls et al, 2003;Avrain et al, 2004;Gilbert et al, 2004;Karlyshev et al, 2005) and mathematical models using MLST data have been generated which suggest that such recombination is frequent. However, the segments of DNA involved are predicted to be far smaller than that found here, with predictions of 3.3 kb (Schouls et al, 2003) and 225-750 bp (Fearnhead et al, 2005).…”

Scientific Opinion on Quantification of the risk posed by broiler meat to human campylobacteriosis in the EU

“…Several of these have been compared for discriminatory power and reproducibility in CAMPYNET studies (Harrington et al, 2003). Genetic events can substantially alter flaA genes (Harrington et al, 1997;Mellmann et al, 2004) and, as a consequence, these genes have minimal relationship to the clonal history of an isolate and even show evidence for substantial cross-species recombination (Dingle et al, 2005). As a result, although allowing a rough prediction of whether or not isolates are identical, flaA RFLP methods are considered not useful for human epidemiological studies.…”

“…Sequencing of a variable portion (the short variable region (SVR)) of the flaA gene is the most common single gene subtyping approach to date (Dingle et al, 2005;Harrington et al, 1997;Meinersmann et al, 1997), although other genes have also been used (Zhang et al, 2000). Two factors limit the inference that can be drawn from flaA sequencing.…”

“…Firstly, identical alleles of the flaA gene fragment have been found in C. jejuni and the related species C. coli (Dingle et al, 2005). Secondly, substantial change can occur in a single recombination so that closely related isolates can have very different flaA sequences (Harrington et al, 1997). Sequence-based approaches have been useful in explicitly demonstrating such limitations of the use of any single gene in a frequently recombining species.…”

Scientific Opinion on the evaluation of molecular typing methods for major food‐borne microbiological hazards and their use for attribution modelling, outbreak investigation and scanning surveillance: Part 1 (evaluation of methods and applications)

“…PCR-RFLP typing has provided limited discrimination. It can also be confounded either by mosaicism due to horizontal gene transfer (e.g., flagellin genes in C. jejuni (Harrington et al, 1997)), or by hypermutation at so-called contingency loci that undergo rapid rearrangements in response to environmental changes. When RFLP analysis is directed at genes encoding ribosomal ribonucleic acid (rRNA) the method is usually referred to as 'Ribotyping'.…”