Comparative in vitro activities of amoxicillin-clavulanic acid, cefuroxime, cephalexin, and cephalothin against trimethoprim-resistant Escherichia coli isolated from stools of children attending day-care centers

A high prevalence of fecal colonization with trimethoprim-resistant Escherichia coli was found in diapered children attending day-care centers in Houston, Tex. In the present study, 100 isolates of E. coli resistant to multiple antibiotics, including trimethoprim (100%), sulfisoxazole (100%), streptomycin (94%), and ampicillin (87%), were obtained over a 5-month period from stool samples of diapered children attending four day-care centers and tested for their susceptibilities to amoxicillin-clavulanic acid, cefuroxime, cephalexin, and cephalothin. The MICs for 50 and 90% of strains tested were 16 and 32 μg/ml, respectively, for amoxicillin-clavulanic acid, 4 and 16 μg/ml, respectively, for cefuroxime, 4 and 64 μg/ml, respectively, for cephalexin, and 32 and >64 μg/ml, respectively, for cephalothin. Although all three oral beta-lactams tested were generally active at concentrations likely to be achieved in urine, cefuroxime and cephalexin were more potent and are thus more likely to be inhibitory at the concentrations needed for systemic infections.