Epidemiology and Infection

Multiresistant Salmonella Typhimurium DT104 infections of humans and domestic animals in the Pacific Northwest of the United States

T. E. BESSER a1c1, M. GOLDOFT a2, L. C. PRITCHETT a3, R. KHAKHRIA a4, D. D. HANCOCK a3, D. H. RICE a3, J. M. GAY a3, W. JOHNSON a4 and C. C. GAY a3
a1 Department of Veterinary Microbiology and Pathology, P.O. Box 647040, Washington State University, Pullman WA 99164-7040, USA
a2 Communicable Disease Epidemiology Section, Washington State Department of Health, 1610 NE 150th St, Shoreline WA 98155, USA
a3 Field Disease Investigation Unit, Washington State University, Pullman WA 99164-7060, USA
a4 National Laboratory for Enteric Pathogens, Health Canada, HPB/IPS Bldg #7 AL, Tunney's Pasture, Ottawa Ontario Canada K1A 0L2


Salmonella Typhimurium definitive type 104 with chromosomally encoded resistance to five or more antimicrobial drugs (R-type ACSSuT+) has been reported increasingly frequently as the cause of human and animal salmonellosis since 1990. Among animal isolates from the northwestern United States (NWUS), R-type ACSSuT+ Typhimurium isolates increased through the early 1990s to comprise 73% of Typhimurium isolates by 1995, but subsequently decreased to comprise only 30% of isolates during 1998. NWUS S. Typhimurium R-type ACSSuT+ were consistently (99%) phage typed as DT104 or the closely related DTu302. S. Typhimurium isolates from cattle with primary salmonellosis, randomly selected from a national repository, from NWUS were more likely to exhibit R-type ACSSuT+ (19/24, 79%) compared to isolates from other quadrants (17/71, 24%; P < 0.01). Human patients infected with R-type ACSSuT+ resided in postal zip code polygons of above average cattle farm density (P < 0.05), while patients infected with other R-types showed no similar tendency. Furthermore, humans infected with R-type ACSSuT+ Typhimurium were more likely to report direct contact with livestock (P < 0.01) than humans infected with other R-types.

(Accepted September 25 1999)

c1 Author for correspondence.