Comparative plasmid profile analysis of Salmonella typhimurium var. Copenhagen strains from a Salmonella outbreak in hospitalized horses]

From April 1990 through June 1991 clinical salmonellosis and asymptomatic faecal excretion of Salmonella spp. were seen in hospitalized horses at two veterinary hospitals. 76 Salmonella strains from hospitalized horses and 18 strains from horses without any clinical contact were characterized by serotyping and plasmid profile analysis. From April 1990 through January 1991 97.8% of the hospitalized horses were infected with strains of S. typhimurium var. Copenhagen, which were closely related according to their similar plasmid patterns. Other strains of S. typhimurium var. Copenhagen and serotype S. enteritidis were isolated not before February 1991. In the same period various plasmid profile types of S. typhimurium var. Copenhagen and strains of S. typhimurium, S. enteritidis and S. lexington were isolated from horses of the control group. Our results suggest that the high incidence of salmonellosis and latent salmonella infection in hospitalized horses was mainly due to the spread of one particular strain of S. typhimurium var. Copenhagen and that this strain was obviously acquired during hospitalisation.