Enterotoxigenicity of Enteropathogenic Serotypes of Escherichia coli Isolated from Infants with Epidemic Diarrhea

Abstract

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

Plasmids coding for drug resistance and localized adherence to HeLa cells in enteropathogenic Escherichia coli O55:H- and O55:H6

“…The mechanisms of virulence of enteropathogenic Escherichia coli (EPEC) have so far not been established. Toxin production (8,9,13) and adherence to human intestinal epithelium (4,15,21) and to cells in culture (4, 5, 10) have been studied. It was shown in our laboratory (16) that E. coli organisms adhere to HeLa cells in two different patterns, called localized adherence (LA) and diffuse adherence.…”

The Canadian contribution to the science of verotoxigenicEscherichia coliand associated illnesses: the early years

“…Using established sera for defining serogroups that were associated with childhood diarrhea and outbreaks of the same, it was evident to many that putative EPEC serogroups could be found in the stool of patients with no or little disease. Among those that were isolated from patients with diarrhea after agglutination serogrouping of E. coli colonies from culture of stool samples, many (if not the majority) could not be demonstrated to be pathogenic by the existing E. coli toxigenicity assays (Klipstein et al 1978). Fleming was one of several who were determined not to relent on the EPEC theme; The Hospital for Sick Children bacteriology laboratory continued to identify EPEC serogroups among stool samples.…”

Toxins

“…In several early reports, cell-free supernatant fluids of EPEC, belonging to serogroups such as 0 2 6 and 0 1 11, gave positive tests in the RILT or HeLa cell test and it would be of interest to examine these strains for VT production. Supernatant fluids of the classic EPEC caused net water secretion in a rat perfusion model but strains from healthy infants did not (Klipstein et al 1978); this toxic effect has not been further investigated. Cell extracts, produced by sonication or disruption in a French press, of many strains of E. coli grown under iron-restricted conditions contain a cytotoxin that acts on HeLa or Vero cells at levels at least 100-fold lower than those obtained from a VT-producing 0157 strain (OBrien et al.…”