Identification of enterotoxigenic Escherichia coli and serum antitoxin activity by the vascular permeability factor assay

Abstract

Twenty five strains of enterotoxigenic (tox+) E. coli isolated in India, Bangladesh, and the U.S.A. were shown to produce vascular permeability factor (PF) activity as well as diarrheagenic activity. Sixteen strains of non enterotoxigenic E. coli were found to be PF negative. The PF response elicited by tox+ E. coli isolated in the U.S.A. from cases of infantile diarrhea was qualitatively different and more difficult to demonstrate. However, this problem was surmounted by assaying 25 fold concentrates of the crude enterotoxin of these strains. PF activity of various strains of tox+ E. coli was neutralized by anti PF antiserum prepared against the enterotoxin of strain H 10407. This anti PF antiserum also neutralized PF activity of V. cholerae enterotoxin. Antiserum containing antibody specific for purified choleragen neutralized E. coli PF activity. These and other results indicate that the PF activity of E. coli is a function of the diarrheagenic enterotoxin as is known to be the case with choleragen. The PF assay can be employed for the identification of tox+ E. coli and for the detection of antitoxic antibody.