Interaction of subminimal inhibitory concentrations of clindamycin and Escherichia coli: effects on adhesion and...

Subinhibitory concentrations (sub-MICs) of clindamycin interfere with the adhesion of Escherichia coli to buccal epithelial cells and promote phagocytosis and killing of this organism by human polymorphonuclear leukocytes (PMNLs). Adherence of E. coli grown in the presence of clindamycin, at concentrations of 2-32 mg/l, varied from 21.1 +/- 7.4 to 25.8 +/- 7.8 bacteria per epithelial cell (EC) (mean +/- S.D.) as compared with 58.3 +/- 10.3 per EC when the organism was cultured in the absence of the antibiotic (P less than 0.01). The number of phagocytosed bacteria per 200 PMNLs increased from 166.1 +/- 36.6 when E. coli was grown in medium 199 containing no antibiotic, to 289.3 +/- 56.4 (P less than 0.01) when the organism was preincubated with 4 mg/l of clindamycin. The same concentration of clindamycin also increased the percentage of phagocytosed bacteria killed by the PMNLs from 42.0 +/- 9.0% to 63.7 +/- 11.2% (P less than 0.01). The results of this study indicate that sub-MICs of clindamycin enhance host-defence mechanisms against E. coli.