A plasmid profile study of Salmonella typhimurium strains isolated from horses in Japan

Sato, G.; Nakaoka, Y.; Marufuji, S.; Ishiguro, N.; Shinagawa, M.

Equine infectious diseases V proceedings of the fifth International Conference: 223-230


Accession: 001740666

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Plasmid profiles were investigated on 230 S. typhimurium strains isolated from horses and their environment on 47 farms in three districts of Hokkaido from 1976 to 1985, and compared with those of 98 isolates from calf salmonellosis in the same district. Three types of plasmid profiles (A, C and D) were found in equine strains, and two of them (A and C) were distributed among equine and bovine strains in two districts. The most prevalent A type profile consisted of 60-, 5.0-, and 3.9- megadalton (MDa) plasmids. The 60-MDa plasmid, either conjugative or nonconjugative, controlled resistance to streptomycin (Sm), sulfadimethoxine (Su), tetracycline (Tc) and kanamycin (Km); the 5.0-MDa plasmid controlled ampicillin (Ap) resistance; and 3.9-MDa plasmid controlled Su resistance. The A type profile strains indicated almost uniform biovars (26e and 26b) and multiresistance (ApSmSuTc(Km)). Although the frequency of conjugative R plasmid differed in the type A strains from horses (28.9%) and cattle (1.4%), genetic and molecular studies of plasmid DNAs of the A type and C type profile revealed similarity between S. typhimurium strains from both animal species. This indicates that S. typhimurium strains from both horses and cattle were closely correlated. The results suggest that one source of equine salmonellosis was calf salmonellosis, previously prevalent in Hokkaido.