Effects of Subinhibitory Antibiotic Concentrations on Porphyromonas gingivalis Fibrinogen and Hemin Binding

Abstract

Porphllromonas gingivalis, a gram-negative anaerobe, is one of the major causative agents in periodontal disease In this study, the effect of sub-inhibitory concentrations of antibiotics on the binding characteristics of P, g ngivalis was examined. P. gingivalis strains 381 and W50 were grown in broth containing one-half the m: nimum inhibitory concentration (MIC) of amoxicillin, doxycycline, metronidazole, penicillin, or tetracycline. Surface hydrophobicity, fibrinogen binding (soluble and immobilized) and hemin binding were evalua :ed. The surface hydrophobicity of strain 381 cultured in each antibiotic decreased, whereas strain W50 showed no statistically significant changes in surface hydrophobicity. All antibiotics used decreased soluble: fibrinogen binding of strain 381. In contrast, all antibiotics, except penicillin, increased binding of soluble: fibrinogen for strain W50. Binding of strain 381 to immobilized fibrinogen increased in the presence of amc iacillin and doxycycline; the binding of strain W50 to immobilized fibrinogen was not affected by any antibic tic. Hemin binding of strain 381 was unaltered by any antibiotic, whereas hemin binding by strain W50 was increased by amoxicillin, metronidazole and penicillin. These observations showed that sub-inhibitory concentrations of antibiotics could confer variable effects on the binding properties of P. gingivalis.