Characteristics of antibiotic-resistant Escherichia coli in the rectum of healthy school-children.

During a 3-year period, 771 rectal swabs were taken from abacteriuric school-children. Out of 709 E. coli strains, each isolated from one faecal specimen, 102 were found to be resistant to one or more antibacterial agents, and 607 to be fully sensitive. Another 204 resistant strains were found by selection for antibiotic resistance. The antibiotic-sensitive and the resistant strains were found to be two somewhat different populations, distinguished by a different distribution of O antigen types. Also, the K1 antigen was more common among the sensitive than among the resistant strains. Resistant strains that were not O typable were very seldom haemolytic.