Ecology of intestinal Escherichia coli in pigs.

The coliflora of three groups of young pigs was shown to be dominated by a small number of Escherichia coli types, as determined by their O antigen, that maintained a tenure of several days or weeks. The pattern of successive waves of E. coli was similar in littermates but, in general, each pig harboured a unique sequence of E. coli types. The E. coli flora from a litter was also shown to be dominated by a small number of E. coli types whose tenure averaged several weeks. A limited amount of information indicated that an enteropathogenic strain of E. coli may occur in this sequence of events and thus appears to be influenced by the same factors as other E. coli strains. The coliflora of two sows appeared to be more complex than those of their progeny and did not seem to follow the same pattern of population change. The coliflora of young pigs differed from the coliflora of man in that there appeared to be no E. coli strains in pigs fitting the description of resident strains.Forty-two percent of all isolates were found to produce colicins and it appeared that this property was more commonly encountered in dominant strains of E. coli