title: A combination of MLST and CRISPR typing reveals dominant Campylobacter jejuni types in organically farmed laying hens.
abstract: OBJECTIVE
  To elucidate the Campylobacter jejuni population in organically farmed laying hens in Finland, multilocus sequence typing (MLST) was combined with characterization of clustered regularly interspaced short palindromic repeat (CRISPR) sequences.
  
  
  RESULTS
  A total of 147 Camp. jejuni isolates, collected from organically farmed laying hens from 18 farms in 2003-2004, were previously analysed by pulsed-field gel electrophoresis. In the present study, subsets of the isolates were further analysed by MLST and CRISPR sequences. Fourteen STs were found by MLST. ST-50 (27%, 7/18 farms), ST-3272 (20%, 8/18 farms), ST-45 (12%, 7/18 farms) and ST-356 (12%, 5/18 farms) were the most common STs. CRISPR types were identical among all isolates of ST-50 (ST-21 clonal complex (CC)) and the most variable among ST-45 (ST-45 CC).
  
  
  CONCLUSIONS
  ST-3272 (UA), a common ST in this study, has been infrequently detected in other hosts. Other major STs (ST-50 and ST-45) have been common in several hosts such as conventional poultry and bovines. CRISPR typing provided additional discrimination between isolates of certain dominant STs and could be useful in further epidemiological studies.
  
  
  CONCLUSIONS
  This study gives new information about MLST and CRISPR types of Camp. jejuni among organically farmed laying hens.
authors.affiliation: Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
authors.forename: S M
authors.initials: SM
authors.lastname: Kovanen
authors.forename: R I
authors.initials: RI
authors.lastname: Kivistö
authors.forename: M
authors.initials: M
authors.lastname: Rossi
authors.forename: M-L
authors.initials: ML
authors.lastname: Hänninen
mesh_terms: D000818:Animals; D001483:Base Sequence; D001715:Bird Diseases / Q000382:microbiology*; D002169:Campylobacter Infections / Q000382:microbiology / Q000662:veterinary*; D016123:Campylobacter jejuni / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D002645:Chickens; D064112:Clustered Regularly Interspaced Short Palindromic Repeats; D004269:DNA, Bacterial / Q000145:classification / Q000235:genetics*; D004531:Eggs / Q000382:microbiology; D005243:Feces / Q000382:microbiology; D005260:Female; D005387:Finland; D005838:Genotype; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing / Q000379:methods; D058871:Organic Agriculture; D010802:Phylogeny
chemical_list: D004269:DNA, Bacterial
keywords: Campylobacter; food safety; molecular epidemiology