Oral Immunization of Mice with a Soluble Protective Antigen obtained from Enteropathogenic Serotypes of Escherichia coli

Abstract

SODIUM deoxycholate extracts were obtained from, strains of enteropathogenic serotypes of Escherichia coli type 0.111 by the following technique: the E. coli. were cultured in a well oxygenated broth culture for 6 h at 37° C. They were centrifuged and washed three times, the suspension was adjusted to give a density of organisms of 1.6 × 10¹⁰, as estimated turbometrically. 2.4 ml. of 1/10 molar ‘Chelaplex’ was then mixed with 210 ml. of this E. coli suspension. While stirring the mixture, 24 ml. of a 20 per cent solution of sodium deoxycholate were added. The lysis of the bacterial cells was checked in the photometer at 540 nm. At an extinction point of 50 per cent the material was centrifuged in a refrigerated centrifuge for 45 min at 20,000g. The surface layer was then dialysed. The dialysate corresponded to an E. coli suspension of 1.2 × 10¹⁰ E. coli/ml. and this antigen was stored frozen at −20° C.