Plasmids and pathogenicity of Salmonella braenderup and Salmonella typhimurium

Research Project

Project/Area Number	61570204
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	細菌学
Research Institution	Tokyo Medical and Dental University School of Medicine
Principal Investigator	HORIUCHI Sankichi Department of Microbiology, Tokyo Medical and Dental University School of Medicine, 医学部微生物学教室, 助手 (60014081)
Project Period (FY)	1986 – 1987
Project Status	Completed (Fiscal Year 1987)
Budget Amount *help	¥2,100,000 (Direct Cost: ¥2,100,000) Fiscal Year 1987: ¥300,000 (Direct Cost: ¥300,000) Fiscal Year 1986: ¥1,800,000 (Direct Cost: ¥1,800,000)
Keywords	Salmonella braenderup / Salmonella typhimurium / Plasmid / Pathogenicity / ウィルレンス / プラスミドと病原性 / サルモネラの病原性
Research Abstract	Correlation of pathogenicity and plasmids of Salmonella braenderup and Salmonella typhimurium isolated from gastroenteritis patients was examined. Of 40 S. braenderup isolates, 38 strains (95%) carried a plasmid of 74 megadalton (Mdal) in size and 17 (31%) of 55 S. typhimurium isolates carried a 60-Mdal plasmid. Plasmid was eliminated from one of the strains by incubaton in L-broth containing ethidium bromide at 42C. Strains of plasmid-bearing and plasmid-eliminated S. braenderup showed similar pathogenicity for invasiveness to HeLa cell, infectivity to the guinea pig eyes, and fluid accumulation in the rabbit ligated ileal loop. Intravenous inoculation of ddY mice with the parent strain produced 100% mortality with characteristic signs of septicemia, whereas inoculation of the plasimd-eliminated strain produced 0% mortality when 10^8 organisms were inoculated. These results suggested that virulence genes for gastroenteritis except for mice lethality are carried by the chromosome of S. braenderup. However, it appeared that the 74・Mdal plasmid may contribute to virulence in mice lethality. The same tests were performed on four strains of S. typhimrium, two of which carried the 60-Mdal plasmid, one of which had been eliminated for plasmid, and one of which was plasmid-free. It was revealed that the 60-Mdal plasmid was not essential for the pathogenicity of S. typhimurium except for the ability evolving mouse typhoid. Scanning electron micrographic studies of the rabbit ligated ileal loops revealed that both of the plasmid-bearing and plasmid-free strins of S. braenderup and S. typhimurium destructed villi and microvilli.