Frequency of enterotoxigenic Escherichia coli in infants during the first three months of life.

To know at what age infants begin to excrete enterotoxigenic Escherichia coli from feces, we studied 30 infants belonging to low socioeconomic status during the first 3 months of life, taking 11 samples of feces from each infant, beginning at the day of birth. We detected LT and ST enterotoxins of E. coli using ELISA test. From the samples studied, 34 samples from 21 (70%) infants were positive for LT. In four samples (1.2%), the presence of LT-producing E. coli coincided with diarrhea, corresponding to three (10.0%) from the infants studied. The earliest age that we observed LT-producing E. coli was day 0 (day of birth). We did not find ST + or LT/ST-producing E. coli strains. We concluded that ETEC strains are frequent findings in healthy infants, and its presence is too early in persons of low socioeconomic status.