THE SYNERGISTIC RELATIONSHIP BETWEEN ANTIBIOTICS AND POLYMORPHONUCLEAR LEUKOCYTES (PMN) IN BACTERICIDAL ACTIVITY

Abstract

The effect of clindamycin on PMN function was investigated in a group of normal adult volunteers who received 1200 mg of clindamycin daily for two days. Neutrophils obtained before and during clindamycin administration were tested for chemotaxis under agarose, phagocytosis and intracellular killing of staphylococci (S. aureus) by the acridine orange staining technique, and oxidative metabolic activity by chemiluminescence generation. Serum-free,washed PMN collected from subjects during clindamycin administration killed significantly greater proportion of S. aureus than the controls (45% vs. 38%, p<.001). The increased bactericidal activity was not related to the serum concentration of clindamycin (mean 1.6 μg/ml) which was well below the MIC for this particular organism. Despite the effect of clindamycin on the intracellular killing of S. aureus, chemotaxis, phagocytosis, and chemiluminescence generation did not differ significantly from the controls. These data suggest significant augmentation of PMN bactericidal activity with clindamycin. Because clindamycin is unique among antibiotics in that it readily enters PMN, it is proposed that PMN may act as vehicles for the transport of antibiotics to the site of infection and thus complement the antibacterial activity of certain antibiotics.