title: Multilocus variable-number tandem-repeat analysis, pulsed-field gel electrophoresis, and antimicrobial susceptibility patterns in discrimination of sporadic and outbreak-related strains of Yersinia enterocolitica.
abstract: BACKGROUND
  We assessed the potential of multilocus variable-number tandem-repeat analysis (MLVA), pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing for discriminating 104 sporadic and outbreak-related Yersinia enterocolitica (YE) bio/serotype 3-4/O:3 and 2/O:9 isolates. MLVA using six VNTR markers was performed in two separate multiplex PCRs, and the fluorescently labeled PCR products were accurately sized on an automated DNA sequencer.
  
  
  RESULTS
  MLVA discriminated 82 sporadic YE 3-4/O:3 and 2/O:9 strains into 77 types, whereas PFGE with the restriction enzyme NotI discriminated the strains into 23 different PFGE pulsotypes. The discriminatory index for a sporadic strain was 0.862 for PFGE and 0.999 for MLVA. MLVA confirmed that a foodborne outbreak in the city of Kotka, Finland in 2003 had been caused by a multiresistant YE 4/O:3 strain that was distinctly different from those of epidemiologically unrelated strains with an identical PFGE pulsotype. The multiresistance of Y. enterocolitica strains (19% of the sporadic strains) correlated significantly (p = 0.002) with travel abroad. All of the multiresistant Y. enterocolitica strains belonged to four PFGE pulsotypes that did not contain any susceptible strains. Resistance to nalidixic acid was related to changes in codons 83 or 87 that stemmed from mutations in the gyrA gene. The conjugation experiments demonstrated that resistance to CHL, STR, and SUL was carried by a conjugative plasmid.
  
  
  CONCLUSIONS
  MLVA using six loci had better discriminatory power than PFGE with the NotI enzyme. MLVA was also a less labor-intensive method than PFGE and the results were easier to analyze. The conjugation experiments demonstrated that a resistance plasmid can easily be transferred between Y. enterocolitica strains. Antimicrobial multiresistance of Y. enterocolitica strains was significantly associated with travel abroad.
authors.affiliation: Department of Infectious Disease Surveillance and Control, Bacteriology Unit, National Institute for Health and Welfare (THL), Helsinki, FI-00271, Finland. leila.sihvonen@thl.fi
authors.forename: Leila M
authors.initials: LM
authors.lastname: Sihvonen
authors.forename: Susanna
authors.initials: S
authors.lastname: Toivonen
authors.forename: Kaisa
authors.initials: K
authors.lastname: Haukka
authors.forename: Markku
authors.initials: M
authors.lastname: Kuusi
authors.forename: Mikael
authors.initials: M
authors.lastname: Skurnik
authors.forename: Anja
authors.initials: A
authors.lastname: Siitonen
mesh_terms: D000328:Adult; D015373:Bacterial Typing Techniques / Q000379:methods; D004269:DNA, Bacterial / Q000235:genetics; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005387:Finland; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D018598:Minisatellite Repeats; D058885:Multilocus Sequence Typing / Q000379:methods; D010957:Plasmids; D017422:Sequence Analysis, DNA; D014195:Travel; D015008:Yersinia enterocolitica / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D004269:DNA, Bacterial