Materials and Methods

Bacterial strains. Twenty-seven isolates of E. coli from various levels of the intestinal tracts of four patients with cholera-like diseases were studied. Samples of intestinal fluid were obtained through a plastic tube from several levels of the gastrointestinal tract both during the acute illness and during convalescence. Details of this procedure and the techniques of culturing have been described previously [3]. In addition, the following isolates also were examined for production of enterotoxin: 10 isolates of E. coli from stools of 10 normal persons living in Calcutta; three isolates of E. coli from jejunal aspirates of three patients with clinical and bacteriologically proven cholera; and two isolates each of strains of Enterobacter and Aeromonas from two of the study cases. Following routine biochemical tests for identification, the organisms were maintained on agar stabs at room temperature without transfer. Serotyping of the strains of E. coli was done in the laboratory of Dr. Mark Lepper, University of Illinois, and at the Center for Disease Control (formerly, the National Communicable Diseases Center), Atlanta, Georgia.