Drug-resistant Escherichia coli and Klebsiella-Enterobacter in healthy adults in Thailand and the effect of antibiotic administration.

Antibiotic-resistant strains of Escherichia coli and, to a lesser extent, Klebsiella-Enterobacter were common in serial samples of the normal intestinal flora of healthy young adults in Thailand, and the resistance often was to multiple drugs and was transferable. Antibiotic administration promoted dominance of the flora by drug-resistant organisms regardless of the drug regimen and the predrug susceptibility pattern of the flora. The normal pattern was regained slowly after the cessation of drug administration.