title: Molecular typing of Salmonella enterica serovar Enteritidis isolates from food-producing animals in Japan by multilocus variable-number tandem repeat analysis: evidence of clonal dissemination and replacement.
abstract: BACKGROUND
  Salmonella enterica serovar Enteritidis is a zoonotic pathogen. Human infections are associated with contaminated eggs and egg products. In Japan, since 1989, the incidence of food-borne disease caused by S. Enteritidis has increased and a pandemic has occurred; however, little is known about changes that occurred before and after this pandemic event in the dominant lineage of isolates from food-producing animals. This study aimed to determine the S. Enteritidis lineages in Japan over the last few decades by using multilocus variable-number tandem repeat analysis (MLVA).
  
  
  RESULTS
  MLVA was used to analyse 79 S. Enteritidis isolates collected from chickens (n = 63), cattle (n = 12), pigs (n = 2), and goats (n = 2) during 1975-2009. The S. Enteritidis isolates showed 14 different MLVA allele combinations, which were classified into two major clusters (A and C) and a minor cluster (B). All the 62 isolates in cluster A were isolated after 1988, whereas 13 of the 17 isolates belonging to cluster B and C were isolated before 1989.
  
  
  CONCLUSIONS
  The MLVA results showed that cluster C was predominant before 1989, and isolates in cluster A disseminated since 1989 and replaced the previous dominant clone, suggesting that isolates of cluster A originated from imported S. Enteritidis infection.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Sayaka
authors.initials: S
authors.lastname: Takahashi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ono
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Tanaka
authors.forename: Masato
authors.initials: M
authors.lastname: Kishima
authors.forename: Masato
authors.initials: M
authors.lastname: Akiba
authors.affiliation: Hokkaido Research Station, National Institute of Animal Health, 4 Hitsujigaoka, Toyohira, Sapporo 062-0045, Hokkaido, Japan. ikuouchi@affrc.go.jp.
authors.forename: Ikuo
authors.initials: I
authors.lastname: Uchida
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000382:microbiology; D002645:Chickens; D015511:Goat Diseases / Q000453:epidemiology / Q000382:microbiology; D006041:Goats; D007564:Japan / Q000453:epidemiology; D018598:Minisatellite Repeats; D058889:Molecular Typing / Q000662:veterinary; D058885:Multilocus Sequence Typing / Q000662:veterinary; D011201:Poultry Diseases / Q000453:epidemiology / Q000382:microbiology; D012481:Salmonella Infections, Animal / Q000453:epidemiology / Q000382:microbiology*; D012477:Salmonella enteritidis / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D012621:Seasons; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology / Q000382:microbiology