Showing papers by "Alison D. O'Brien published in 1986"

Two toxin-converting phages from Escherichia coli O157:H7 strain 933 encode antigenically distinct toxins with similar biologic activities.

Abstract: Escherichia coli O157:H7 strain 933 contains two distinct toxin-converting phages (933J and 933W). The biologic activities and antigenic relationship between the toxins produced by 933J and 933W lysogens of E. coli K-12, as well as the homology of the genes that encode the two toxins, were examined in this study. The 933J and 933W toxins, like Shiga toxin produced by Shigella dysenteriae type 1, were cytotoxic for the same cell lines, caused paralysis and death in mice, and caused fluid accumulation in rabbit ileal segments. The cytotoxic activity of 933J toxin for HeLa cells was neutralized by anti-Shiga toxin, whereas the activity of 933W toxin was not neutralized by this antiserum. In contrast, an antiserum prepared against E. coli K-12(933W) neutralized 933W toxin but not 933J toxin or Shiga toxin. For E. coli 933, most of the cell-associated cytotoxin was neutralized by anti-Shiga toxin, whereas most of the extracellular cytotoxin was neutralized by anti-933W toxin. However, a mixture of these antisera indicated the presence of both toxins in cell lysates and culture supernatants. Among 50 elevated cytotoxin-producing strains of E. coli, we identified 11 strains isolated from cases of diarrhea, hemorrhagic colitis, or hemolytic uremic syndrome that produced cell-associated cytotoxins which were neutralized by the 933W antitoxin. Southern hybridization studies showed that the cloned toxin structural genes from phage 933J hybridized with DNA from phage 933W under conditions estimated to allow no more than 26% base-pair mismatch. These findings indicate that E. coli produces two genetically related but antigenically distinct cytotoxins with similar biologic activities which we propose to name Shiga-like toxins I and II. Strains of E. coli that produce elevated levels of Shiga-like toxin I or Shiga-like toxin II, or both, have been associated with the clinical syndromes of diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. Images

Production of Shiga-Like Toxin by Escherichia coli

Abstract: Escherichia coli is one of several agents that cause intestinal disease in humans and animals. Four classes of E. coli have been recognized [1], Enterotoxigenic E. coli (ETEC) strains produce a heat-labile (LT) enterotoxin and/or a heat-stable (ST) enterotoxin. Enteroinvasive E. coli (EIEC) strains, like shigellae, penetrate and multiply within epithelial cells. Enteropathogenic E. coli (EPEC) strains belong to certain serogroups that have been incriminated as pathogens by epidemiological studies. Some EPEC strains have been shown to adhere to cells of the intestinal mucosa and to produce pathognomonic lesions at the site of attachment. Enterohemorrhagic E. coli (EHEC) strains cause a distinct clinical syndrome (hemorrhagic colitis), and serotype 0157:H7 has been associated with this illness. Neither EPEC nor EHEC strains produce classic enterotoxins, nor are they enteroinvasive. Some strains of E. coli produce a cell-associated cytotoxin that is neutralized by antibodies against purified Shiga toxin from Shigella dysenteriae type 1 [2-4]. The cytotoxins purified from one EPEC strain 026:H11 (H30) and from one EHEC strain 0157:H7 (933) have biologic activities (cytotoxicity for HeLa and Vero cells, lethality for mice, and enterotoxicity for ligated ileal segments from rabbits) and subunit structures similar to those of Shiga toxin [5, 6]. The purpose of this study was to determine the frequency and levels of cytotoxin production for a wide variety of E. coli strains. Culture supernatants and sonic lysates of 418 strains isolated from humans, animals, ajid food were examined for cytotoxic effects on HeLa cells and to see whether cytotoxicity could be neutralized by antibodies to Shiga toxin.

Growth of Escherichia coli in the presence of trimethoprim-sulfamethoxazole facilitates detection of Shiga-like toxin producing strains by colony blot assay

Abstract: Subinhibitory concentrations of trimethoprim-sulfamethoxazole increased the total yield of Shiga-like toxin (SLT), produced by Shigella dysenteria 1 and by enterophathogenic and enterohemorrhagic strains of Escherichia coli . Stimulation of SLT synthesis by trimethoprim-sulfamethoxazole was demonstrated by an increase in cytotoxic activity for HeLa cells and the diameter of the zone formed around bacterial colonies probed with monoclonal antibodies to SLT. Thus, supplementation of culture media with trimetroprimsulfamethoxazol will facilitate SLT purification and detection of SLT-producing bacteria.

Influence of Host Genes on Resistance of Inbred Mice to Lethal Infection with Salmonella typhimurium

Abstract: Salmonella typhi, the causative agent of typhoid fever, is avirulent for mice. The parenteral 50% lethal dose (LD50) of S. typhi for mice of all inbred strains examined to date is ≥108 bacteria (Gerichter 1960; Carter and Collins 1974a; O’Brien 1982) unless the animals are pretreated with iron and/or an iron chelater (Powell et al. 1980; O’Brien 1982) or the mice are challenged intraperitoneally with S. typhi suspended in hog gastric mucin (Nungester et al. 1936; Spaun 1964). By contrast, Salmonella typhimurium primarily evokes gastroenteritis in man, but causes a typhoid fever-like disease in mice (called murine typhoid). Both human typhoid and murine typhoid are systemic illnesses. In mice infected orally with S. typhimurium or in humans who ingest food or water contaminated with S. typhi, the bacteria either multiply in the small bowel or directly penetrate the intestinal mucosa without apparent enteric colonization (Gerichter 1960; Hornick etal. 1970; Hohman 1978). Studies in mice have established that the foci from which salmonellae disseminate are the Peyer’s patches of the small intestine (Carter and Collins 1974b; Hohman et al. 1978). The bacteria apparently gain access to the circulation via the lymphatics, seed the reticuloendothelial cell system (RES), and replicate within splenic and hepatic tissues.

Susceptibility of Mus musculus musculus (Czech I) mice to Salmonella typhimurium infection.

Abstract: When inbred or outbred mice are challenged with Salmonella typhimurium, they develop a disease which is similar in its pathogenesis to typhoid fever in man. Whether the animals ultimately survive the infection depends on the virulence of the bacterial strain, the route of challenge, and the genetic constitution of the mice. Although mice of some inbred strains and many outbred strains survive parenteral inoculation with up to 10,000 virulent salmonellae, mice of other inbred strains invariably succumb to low-dose (< 10 bacteria) challenge. Several distinct host genes have been identified which regulate this differential susceptibility to murine typhoid. Some of these genes act early in the course of the disease (Ity, Lps, and the C3HeB/FeJ gene), and mice that express the, susceptibility allele at any one of these loci (e.g., Ity S or Lps d ) usually die by day 10 of infection with a virulent strain of S. typhimurium (Plant and Glynn 1976; Hormaeche 1979; O’Brien et al. 1980, O’Brien and Rosenstreich 1983).