title: Investigating the host specificity of Campylobacter jejuni and Campylobacter coli by sequencing gyrase subunit A.
abstract: BACKGROUND
  Surveillance and field investigations of Campylobacter infections require molecular tools with genetic markers appropriate for tracing purposes, i.e. based on the principle that some Campylobacter lineages acquire a host signature under adaptive selection pressure. We developed a sequence-based method targeting the quinolone resistance determining region within the subunit A of DNA gyrase (gyrA). Host specificity was evaluated by characterizing two collections of Campylobacter jejuni (N = 430) and Campylobacter coli (N = 302) originating from surface waters, domestic mammals and poultry.
  
  
  RESULTS
  Based on nucleotide identity, a total of 80 gyrA alleles were observed. Thirty nine alleles assigned to C. coli encoding two peptides fell into three clades: two associated with surface waters and one associated with domestic mammals and poultry. The variability in GC content generated by synonymous mutations suggested that surface waters isolates originated from two distinct ecological niches. A total of 42 alleles were recorded from C. jejuni strains and encoded 8 peptides including one lying in a distinct lineage associated with wildlife. Seven of the 23 alleles encoding peptide #1 displayed the synonymous mutation G408A not identified in poultry isolates. By contrast, the substitution Ser22Gly observed in 4 different peptide groups was significantly associated with domestic birds (P = 0.001). The change in amino acid sequences Thr86Ile conferring resistance to quinolones was significantly associated with poultry (P < 0.001) in both C. jejuni and C. coli with 38.7% and 67.9% of quinolone-resistant strains, respectively.
  
  
  CONCLUSIONS
  The gyrA typing method presented here is an informative tool as sequences appear to be predictive of particular ecological niches. Combined with multi-locus sequence typing, it could increase the resolution of source attribution, and combined with porA/flaA typing it could be suitable for detecting temporal clusters of human cases. All gyrA alleles identified were deposited in the freely accessible online database http://pubmlst.org/campylobacter.
authors.affiliation: National Health Laboratory, Surveillance and Epidemiology of Infectious Diseases, 1 rue Louis Rech, Dudelange L-3555, Luxembourg. catherine.ragimbeau@lns.etat.lu.
authors.forename: Catherine
authors.initials: C
authors.lastname: Ragimbeau
authors.forename: Stephanie
authors.initials: S
authors.lastname: Colin
authors.forename: Anthony
authors.initials: A
authors.lastname: Devaux
authors.forename: Frédéric
authors.initials: F
authors.lastname: Decruyenaere
authors.forename: Henry-Michel
authors.initials: HM
authors.lastname: Cauchie
authors.forename: Serge
authors.initials: S
authors.lastname: Losch
authors.forename: Christian
authors.initials: C
authors.lastname: Penny
authors.forename: Joël
authors.initials: J
authors.lastname: Mossong
mesh_terms: D000483:Alleles; D000818:Animals; D000829:Animals, Domestic; D001482:Base Composition; D017000:Campylobacter coli / Q000145:classification / Q000201:enzymology* / Q000302:isolation & purification / Q000502:physiology*; D016123:Campylobacter jejuni / Q000145:classification / Q000201:enzymology* / Q000302:isolation & purification / Q000502:physiology*; D016000:Cluster Analysis; D027081:DNA Gyrase / Q000235:genetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005838:Genotype; D058507:Host Specificity; D006801:Humans; D008322:Mammals; D058889:Molecular Typing / Q000379:methods*; D011200:Poultry; D017422:Sequence Analysis, DNA; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; D027081:DNA Gyrase