Erythromycin, miocamycin and clindamycin towards adhesivity and phagocytosis of gram-positive bacteria.

To estimate the antibacterial activity of sub-MIC concentrations of Erythromycin and Miocamycin in the mucosal surfaces, we studied the adhesivity of Gram-positive pathogenic strains (S. pyogenes, S. aureus) towards oral and urinary epithelial cells. Erythromycin strongly inhibits the adhesivity of Staphylococci to oral cells (50% of inhibition) and to a lesser extent the adhesivity of Streptococci (21%), while Miocamycin reduced the adhesivity of Staphylococci by about 16%. In some cases, an increase in the adhesivity on urinary cells was found mainly for Miocamycin. Therefore Erythromycin, at sub-MIC concentrations, is able to induce a marked reduction in the adhesivity of Staphylococci and Streptococci; this may interfere with the invasivity and subsequent pathogenicity of these bacteria. As far as phagocytosis is concerned, one strain of enterotoxic coagulase + S. aureus bearing A-protein on its surface but lacking the capsule was taken into consideration. The presence of A-protein induces resistance to phagocytosis and opsonization by normal serum. The addition of antibiotics which inhibit protein biosynthesis, such as Clindamycin, Miocamycin and Erythromycin, increases either uptake of this strain or intracellular killing. In particular Clindamycin and Erythromycin, at sub-MIC concentrations, are able to affect the interaction of Staphylococcus with phagocytic cells.