The effect of antibacterial agents on the association between bacteria and leukocytes.

The effect of antibacterial agents on human lymphocyte chemotaxis, phagocytic capacity, protein synthesis and the relation between morphologic and functional changes induced by antibacterial agents was studied. A significant depression of chemotaxis measured with an agarose gel technique was detected when human leukocytes were incubated with fusidic acid and rifampicin in clinically obtainable concentrations. The newer, well absorbed tetracyclines depressed chemotaxis at high concentrations, but a less pronounced inhibition was detected with classical tetracycline. The incorporation by human neutrophils of 14C-leucine into a trichloroacid insoluble fraction was markedly depressed by the same antibiotics, and it is suggested that some antibiotics acting by inhibition of protein synthesis also affect chemotaxis of human neutrophils. Doxycycline, but not lymecycline, initially decreased granulocyte adherence to glass surfaces. After 20 min of incubation granulocytes treated with both doxycycline and lymecycline adhered in higher numbers than control cells. Human leukocytes incubated with tetracycline hydrochloride or doxycycline in vitro showed a decreased capacity to phagocytize yeast and bacteria. Furthermore, leukocytes harvested from healthy volunteers after ingestion of tetracycline also demonstrated decreased phagocytic capacity. Scanning electron micrographic studies showed changed surface morphology for granulocytes incubated with tetracyclines, which might explain the changed adherence and phagocytosis by tetracycline-treated cells.