Congo red binding test in enteroinvasive and nonpathogenic Escherichia coli strains.
Out of 6 variants the appropriate media to perform Congo red binding test for enteroinvasive E. coli strains were established (trypto-soy agar Eiken, T.S.A.--Cantacuzino Institute and B.T.S.D.). 12 E. coli strains belonging to enteroinvasive O-serogroups formed on Congo red agar red-coloured, non-coloured colonies or both; cultures from 59 red colonies and 61 white colonies were inoculated in guinea pig eyes. The correlation between positive Congo red binding test and positive Sereny test was 91% (out of 59 red colonies, 47 evoked keratoconjunctivitis in both infected eyes and 7 in only one eye). The negative Congo red binding test corresponds (98.4%) to the failure to induce illness in the guinea pigs' eye (only one out of 61 Crb = colonies was Sereny positive, evoking keratoconjunctivitis in only one of the two infected eyes of a guinea pig). Comparing in vivo lack of pathogenicity in 44 E. coli strains isolated from human normal intestinal flora and negative Congo red binding test, a correlation of 72.73% on B.T.S.D. and 65.91% on T.S.A. medium was found. Developing an appropriate method based on Crb test about 70% of the nonpathogenic E. coli colonies could be eliminated from the laborious agglutination with enteroinvasive O-serogroups E. coli antisera.
Pencu
E
E
Cantacuzino Institute, Bucharest, Romania.
Ciudin
L
L
Tonciu
M
M
Mihai
I
I
D000818:Animals; D001431:Bacteriological Techniques; D003224:Congo Red / Q000493:pharmacokinetics; D004926:Escherichia coli / Q000302:isolation & purification / Q000378:metabolism / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology; D006168:Guinea Pigs; D006801:Humans; D007422:Intestines / Q000382:microbiology; D007637:Keratoconjunctivitis / Q000382:microbiology; D014774:Virulence
D003224:Congo Red