Studies by various investigators of infants from whom enteropathogenic Escherichia coli (EPEC) were isolated reveal that many infants were in the first weeks of life and that the majority had an associated diarrhea. Cathie and MacFarlane1 (1951) studied 264 cases of infantile diarrhea and found E. coli O111:B4 in stool cultures of 16.7% in each of the first two months of life. Shanks and Studzinski 2 (1952) studied 158 infants with diarrhea, culturing stools for E. coli 055 :B5 and O111:B4, and found these serotypes in 25.0% of infants under 4 weeks of age. Thomson, Watkins, and Gray3 (1956) searched for E. coli O26:B6, 055 :B5, and O111:B4 in a group of infants, 77.0% of whom were in the first three months of life, and they found 20 infants (18.0%) harboring one of these three types. In 8 of these 20 infants there was an associated diarrhea. Curtin and Clifford4 (1956), in a study to determine the incidence of E. coli 026: ß, 055:B5, 0111:B4, and 0127:B8 among neonatal patients, detected 2 of 91 in¬ fants in the first week of life excreting Types 026:Be and 055 :B5, respectively. These two infants did not have diarrhea at the time stool was obtained for culture. Cooper, Keller, and Walters5 (1957) studied 169 infant patients, the majority with diarrhea, from whom one of nine serotypes of EPEC were isolated, and found that 43.8% were in their first three months of life. A recent review and classification of these infants according to their ages by weeks reveals that in the first, second, third, and fourth weeks of age, there were four, six, six, and five infants, respectively, all but one with diar¬ rhea. In the second, third, fourth, fifth, sixth, and seventh months of life there were 23, 27, 18, 16, 7, and 5 infants, respectively, and all but 6 had diarrhea. Since the source of infection of young infants is usually unknown, except in insti¬ tutional epidemics, and since a significant number of cases of diarrhea associated with the presence of EPEC occur early in life when the infants have limited opportunity for exposure, the question arises regarding the source of infection in their immediate environment. We wondered whether moth¬ ers, who are usually in closest contact with the infants, might be the sources of infec¬ tion, perhaps as asymptomatic intestinal carriers. Our previous experience, as well as that of others, has shown that an occa¬ sional adult harbors EPEC in the intestinal tract without evidence of infection, espe¬ cially in epidemics of diarrhea in infants,
