Molecular Characterization ofCampylobacter jejuniClones: A Basis for Epidemiologic Investigation

Abstract

A total of 814 isolates of the foodborne pathogen Campylobacter jejuni were characterized by multilocus sequence typing (MLST) and analysis of the variation of two cell-surface components: the heat-stable (HS) serotyping antigen and the flagella protein FlaA short variable region (SVR). We identified 379 combinations of the MLST loci (sequence types) and 215 combinations of the cell-surface components among these isolates, which had been obtained from human disease, animals, food, and the environment. Despite this diversity, 748 (92%) of the isolates belonged to one of 17 clonal complexes, 6 of which contained many (318, 63%) of the human disease isolates. Several clonal complexes exhibited associations with isolation source or particular cell-surface components; however, the latter were poorly predictive of clonal complex. These data demonstrate that the clonal complex, as defined by MLST, is an epidemiologically relevant unit for both long and short-term investigations of C. jejuni epidemiology.

Campylobacter sequence typing databases: applications and future prospects

“…As a consequence of this, these organisms do not exhibit a clonal population structure (Levin, 1981), but are partially clonal (Maynard Smith et al, 1993), and their populations are dominated by clusters of related genotypes which are recognised by MLST as clonal complexes. Although clonal complexes are pragmatically defined, as described above, they nevertheless have the strength that they reflect the genealogy of the species (Sheppard et al, 2010a(Sheppard et al, , 2011a and have become major units of analysis for Campylobacter populations (Dingle et al, 2002). Intriguingly, the two species have different population structures: C. jejuni populations comprise many clonal complexes with little evidence of any phylogenetic relationship among them; although there are some groups of phylogenetic relationships among some clonal complexes, there is little evidence of a clonal frame linking all clonal complexes .…”

“…These can be sequence-typed in combination with MLST, for example to detect strains responsible for disease outbreaks (Clark et al, 2005;Dingle et al, 2002Dingle et al, , 2008Meinersmann et al, 1997;Sails et al, 2003a). The diversity in the nucleotide sequences of these gene regions, which are under positive (diversifying) selection, is much greater than that seen amongst housekeeping genes, which are under stabilizing selection, and so for the antigens allele designations are given for both nucleotide sequences and the translated peptide sequences which they encode.…”

“…2). For many bacteria, including Campylobacter, these informally defined groupings have proven useful units of analysis Dingle et al, 2002). MLST data consisting of all alleles described to date, together with provenance data for isolates with new STs, are distributed via the internet-accessible, curated database http://pubmlst.…”

Identification and interrogation of highly informative single nucleotide polymorphism sets defined by bacterial multilocus sequence typing databases

“…Therefore, MLST databases for a number of different species were searched for high-D SNP sets. Species subject to this analysis were Burkholderia pseudomallei/ Burkholderia mallei, Helicobacter pylori, Campylobacter jejuni, Streptococcus pneumoniae, Streptococcus pyogenes and Enterococcus faecium (Feil et al, 2000;Enright et al, 2001;Sa-Leao et al, 2001;Dingle et al, 2002;Homan et al, 2002;Godoy et al, 2003;Meats et al, 2003). Ten different sets of SNPs were identified for each species.…”

Risk factors for infection withCampylobacter jejuni flaAgenotypes

“…There are reports of instability in the flaA locus [41] but the majority of C. jejuni isolates are apparently genetically stable in this region over time [26,42,43] and that instability may be strain specific. Sequence-based methods such as MLST remove dependence on visual and potentially subjective, genotype assignment but require expensive equipment to handle medium to high numbers of isolates and reagents are costly [29,44]. Isolates from this study were genotyped retrospectively, but 'real time', genotyping of notified case isolates would be preferable, to enable rapid detection of temporal clusters using a library of common flaA genotypes and should be feasible.…”