Epidemiologic study of results of pulsed-field gel electrophoresis of isolates of Rhodococcus equi obtained from horses and horse farms.
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.
Cohen
Noah D
ND
Department of Large Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4475, USA.
Smith
Karen E
KE
Ficht
Thomas A
TA
Takai
Shinji
S
Libal
Melissa C
MC
West
Brian R
BR
DelRosario
Lemuel S
LS
Becu
Teotimu
T
Leadon
Desmond P
DP
Buckley
Thomas
T
Chaffin
M Keith
MK
Martens
Ronald J
RJ
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
D004269:DNA, Bacterial