COMMON PLASMID ENCODING RESISTANCE TO AMPICILLIN, CHLORAMPHENICOL, GENTAMICIN, AND TRIMETHOPRIM-SULFADIAZINE IN 2 SEROTYPES OF SALMONELLA ISOLATED DURING AN OUTBREAK OF EQUINE SALMONELLOSIS

  • 1 January 1985
    • journal article
    • research article
    • Vol. 46  (4) , 769-773
Abstract
An outbreak of equine salmonellosis occurred at the Veterinary Medical Teaching Hospital, University of California, Davis [USA], between June 1981 and March 1982. Forty-four horses were infected with S. saint-paul, a serotype rarely isolated from animals at the university before the outbreak. Unlike the isolates of S. saint-paul obtained at the beginning of the outbreak, almost all strains isolated near the end were resistant to ampicillin, cephalothin, chloramphenicol, gentamicin, kanamycin, sulfadiazine, trimethoprim and trimethoprim-sulfadiazine. A conjugal-resistance plasmid (R-plasmid) was responsible for resistance to these antimicrobics. This R-plasmid was identical to an R-plasmid of S. krefeld, a serotype that had been isolated repeatedly throughout the hospital before, during, and after the outbreak involving S. saint-paul. This finding promoted the suggestion that in vivo transfer of the R-plasmid had occurred. Whether the donor organism was S. krefeld is unknown.