Effect of ciprofloxacin on phagocytosis.

Certain aspects of the relationship between host defence mechanisms and the new quinoline derivative ciprofloxacin in comparison to norfloxacin and ofloxacin were studied. Ciprofloxacin did not affect chemotaxis of human polymorphonuclear leucocytes in agarose. In leucocytes exposed to ciprofloxacin, norfloxacin and ofloxacin neither the chemiluminescent response to opsonized zymosan and formyl-methionyl-leucyl-phenylalanine nor the phagocytic or bactericidal activity was affected. However, killing of Staphylococcus aureus by human polymorphonuclear leucocytes exposed to subinhibitory concentrations of ciprofloxacin was enhanced. The results show that the quinolines tested do not directly influence phagocytic cells, but a subinhibitory concentration can make bacteria more susceptible to phagocytosis and killing.