The pathogenic properties of 20 strains of Campylobacter jejuni isolated from persons with clearly defined clinical manifestations were determined. Cell-free broth filtrates were examined for (i) enterotoxin production by Chinese hamster tissue culture assay and an enzyme-linked immunosorbent assay (ELISA) employing GM1 ganglioside and affinity-purified antiserum to Escherichia coli heat-labile toxin, (ii) cytotoxin production by Vero and HeLa cell tissue culture lines, and (iii) their ability to cause fluid secretion in rat ligated ileal loops. Viable bacteria were examined for invasive properties by an ELISA with the immunoglobulin fraction of antiserum to Formalin-killed bacteria of an invasive strain, and by their effect on fluid secretion and morphology in rat ligated ileal loops. None of the eight isolates obtained from asymptomatic carriers had any detectable pathogenic properties. All six strains isolated from persons with bloody invasive-type diarrhea elaborated a cytotoxin; their viable bacteria had high titers in the ELISA for invasive properties and caused fluid secretion in ligated ileal loops, although consistent morphologic abnormalities and evidence of mucosal invasion, examined by immunofluorescence techniques, were not detected. All six strains isolated from persons with watery secretory-type diarrhea produced an enterotoxin, one elaborated a cytotoxin, and broth filtrates of all strains caused fluid secretion in ligated ileal loops; viable bacteria had low titers in the ELISA for invasive properties and evoked fluid secretion in ligated loops by means of enterotoxin production. These observations show (i) that a correlation exists between the pathogenic properties of the infective C. jejuni strain and gastrointestinal manifestations in the infected host, and (ii) that these pathogenic properties can be identified by in vitro assays, including ELISAs.

The enterotoxigenicity of 12 strains of coliform bacteria (Enterobacter cloacae, Klebsiella pneumoniae, and Escherichia coli) isolated from the gastrointestinal (GI) tract of persons with either acute diarrhea or tropical sprue and of 13 strains of the same species isolated from urine (GU) cultures was determined. Fractions of heat-labile (LT) and heat-stable (ST) toxins of each strain were separated by ultrafiltration, and the effect of graded concentrations (range, 100 microgram-10 pg/ml) on water transport was assessed by in vivo perfusion in the rat jejunum. Enterotoxigenic activity was defined as inducement of net secretion of water. All 12 of the GI strains and six of 13 GU strains elaborated enterotoxins, but there was a millionfold quantitative difference in the potency of the toxins produced. All of the GI strains produced one or both forms of toxin, which had a minimal effective concentration of as low as 0.1-10 ng/ml, whereas the GU strains produced toxins of weak or, rarely, of intermediate potency.

Enteropathogenic serotypes of Escherichia coli which have been incriminated by epidemiological evidence as responsible for epidemics of acute diarrhea in infants are often found to be nontoxigenic when tested by conventional systems such as Y1-adrenal, Chinese hamster ovary, and suckling mouse assays. Twelve such strains, representing four different enteropathogenic serotypes, were examined for their capacity to elaborate toxic materials which alter water transport. Ultrafiltration fractions prepared to contain either a high-molecular-weight, heatlabile or a low-molecular-weight, heat-stable form of toxin from each strain were perfused through rat jejuna in graded concentrations ranging from 100 ftg to 0.1 ng/ml. Ten of the twelve enteropathogenic strains produced one or both toxin forms that induced water secretion at concentrations of 1 to 10 ng/ml. Values in this range are considered indicative of clinically significant enterotoxigenicity in this assay system, and toxins from well-documented toxigenic strains examined in this study were active at these same concentrations. Similar preparations from ten control strains from healthy persons were either inactive or evoked water secretion only at concentrations of 10 to 100 ,g/ml. These observations suggest that enteropathogenic serotypes of E. coli isolated from epidemics of infantile diarrhea produce diarrhea by elaborating potent heat-labile and heat-stable toxin forms which alter water transport but which are inactive in conventional assay systems. The manner in which these toxins differ either quantitatively or qualitatively from those which stimulate the conventional test systems is unknown.on August 5, 2020 by guest http://iai.asm.org/ Downloaded from

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