title: Epidemiologic study of results of pulsed-field gel electrophoresis of isolates of Rhodococcus equi obtained from horses and horse farms.
abstract: OBJECTIVE
  To compare isolates of Rhodococcus equi on the basis of geographic source and virulence status by use of pulsed-field gel electrophoresis (PFGE).
  
  
  METHODS
  290 isolates of R equi (218 virulent isolates from foals and 72 avirulent isolates from feces, soil, and respiratory tract samples) obtained between 1985 and 2000 from horses and horse farms from 4 countries.
  
  
  METHODS
  DNA from isolates was digested with the restriction enzyme Asel and tested by use of PFGE. Products were analyzed for similarities in banding patterns by use of dendrograms. A similarity matrix was constructed for isolates, and the matrix was tested for nonrandom distributions of similarity values with respect to groupings of interest.
  
  
  RESULTS
  There was little grouping of isolates on the basis of country, virulence status, or region within Texas. Isolates of R equi were generally < 80% similar, as determined by use of PFGE. Isolates from the same farm generally were rarely of the same strain.
  
  
  CONCLUSIONS
  Considerable chromosomal variability exists among isolates of R equiobtained from the same farm, sites withinTexas, or among countries from various continents. Only rarely will it be possible to link infections to a given site or region on the basis of analysis of isolates by use of PFGE of chromosomal DNA.
authors.affiliation: Department of Large Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4475, USA.
authors.forename: Noah D
authors.initials: ND
authors.lastname: Cohen
authors.forename: Karen E
authors.initials: KE
authors.lastname: Smith
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Ficht
authors.forename: Shinji
authors.initials: S
authors.lastname: Takai
authors.forename: Melissa C
authors.initials: MC
authors.lastname: Libal
authors.forename: Brian R
authors.initials: BR
authors.lastname: West
authors.forename: Lemuel S
authors.initials: LS
authors.lastname: DelRosario
authors.forename: Teotimu
authors.initials: T
authors.lastname: Becu
authors.forename: Desmond P
authors.initials: DP
authors.lastname: Leadon
authors.forename: Thomas
authors.initials: T
authors.lastname: Buckley
authors.forename: M Keith
authors.initials: MK
authors.lastname: Chaffin
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Martens
mesh_terms: D000193:Actinomycetales Infections / Q000453:epidemiology / Q000382:microbiology* / Q000662:veterinary*; D000818:Animals; D001118:Argentina / Q000453:epidemiology; D004269:DNA, Bacterial / Q000032:analysis; D016521:Electrophoresis, Gel, Pulsed-Field; D019143:Evolution, Molecular; D006734:Horse Diseases / Q000382:microbiology*; D006736:Horses / Q000382:microbiology; D007494:Ireland / Q000453:epidemiology; D007564:Japan / Q000453:epidemiology; D010802:Phylogeny; D016929:Rhodococcus equi / Q000235:genetics* / Q000302:isolation & purification* / Q000472:pathogenicity; D013781:Texas / Q000453:epidemiology; D014774:Virulence
chemical_list: D004269:DNA, Bacterial