Increasing Resistance to Trimethoprim-Sulfamethoxazole Among Isolates of Escherichia coli in Developing Countries

observed among E. coli isolated at a pediatric hospital in Santiago, Chile, and a 40% resistance rate at a general teaching hospital in Bangkok, Thailand. Most isolates were from urinary tract infections and showed high-level resistance (minimal inhibitory concentration of TMP >1,000 pg/ml). Nineteen of 35 isolates tested transferred resistance to TMP; most cotransferred resistance to streptomycin and sulfonamides. Dihydrofolate reductase type I was detected by gene probing in 14 of 35 strains. Subsequent investigatiors in Brazil, Honduras, and Costa Rica revealed that this high rate of resistance was not an isolated phenomenon.