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Epidemiology and Infection (1999), 122 : 479-484 Cambridge University Press
doi:10.1017/S0950268899002496
 
Research Article

Genetic subtyping of Escherichia coli O157 isolates from 41 Pacific Northwest USA cattle farms

D. H. RICE a1 c1 , K. M. McMENAMIN a1 , L. C. PRITCHETT a1 , D. D. HANCOCK a1 and T. E. BESSER a2
a1 Field Disease Investigation Unit, Department of Veterinary Clinical Sciences, Washington State University, Pullman, WA 99164-7060
a2 Department of Veterinary Microbiology and Pathology, Washington State University; Pullman, WA 99164-7040

Abstract

Escherichia coli O157 (n = 376) from 41 cattle farms were subtyped using pulsed field gel electrophoresis of endonuclease cleaved chromosomal DNA. Cleavage with XbaI resulted in 81 subtypes. Fifty-one isolates from subtypes found in more than one herd, or in herds on multiple sample collection dates were compared using the endonuclease NotI, resulting in 23 additional subtypes. Up to 11 XbaI subtypes were found per farm with up to 7 subtypes/farm identified from a single date. Indistinguishable subtypes (both XbaI and NotI) were found to persist on 4 farms for 6–24 months. Five subtypes were found on more than one farm separated by up to 640 km. Dairy farms where cattle had moved onto the farm had a similar number of subtypes as farms with no movement of cattle, and feedlots had more subtypes than dairy farms. These data indicate that there is a mechanism for multiple herd exposure to specific subtypes, there are multiple sources of exposure for cattle on farms, and on-farm reservoirs other than cattle may exist.

(Accepted February 22 1999)


Correspondence:

c1 Author for correspondence.


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