Effects of Subminimal Inhibitory Concentrations of Antibiotics on Adhesiveness of Escherichia coli in Vitro*

The adhesion of radiolabeled Escherichia coli (strain SS142) to monolayers of Intestine 407, a human epithelioid tissue culture cell line, was investigated. In this assay the adhesion of bacteria grown in the presence of subminimal inhibitory concentrations of tetracycline, clindamycin,, or trimethoprim-sulfametrole was reduced in a manner that was dose dependent. In contrast, at such concentrations nalidixic acid enhanced the adhesion of this bacterial strain, and other antibiotics-e.g., penicillin G, ampicillin, mecillinam, cephacetrile, cephalexin, cefotaxime, chloramphenicol, and streptomycin-did not affect its adhesiveness.