Selective growth inhibition of Porphyromonas gingivalis by bestatin

Recent work in our laboratory indicates that selected protease/peptidase inhibitors interfere with the growth of Porphyromonas gingivalis. The aim of the present study was to further investigate the inhibitory effect of bestatin on the growth of P. gingivalis. Complete growth inhibition of P. gingivalis (11 strains) was observed when bestatin was incorporated at 2.5 micrograms ml-1 in a complex broth medium. Fifty percent inhibition was still obtained with bestatin at a final concentration of 0.5 microgram ml-1. The inhibitory effect of bestatin was highly specific as the growth of 20 different oral bacterial species, including Gram-positive and Gram-negative as well as saccharolytic and asaccharoltic bacteria, was not affected even at bestatin concentrations up to 50 micrograms ml-1. Bestatin did not significantly affect the viability of P. gingivalis indicating that it has a bacteriostatic rather than a bactericidal effect. Growth assays using other specific inhibitors suggested that the effect of bestatin on the growth of P. gingivalis was unlikely to be related to its aminopeptidase inhibitor activity. Cultivation of P. gingivalis with a subinhibitory concentration of bestatin did not modify the cell envelope protein profile, as determined by SDS-PAGE analysis, but significantly decreased the number of extracellular vesicles produced. The present study indicated that bestatin is a highly effective inhibitor of cell growth of P. gingivalis. Additional studies will indicate whether bestatin should be considered as a potential drug in the control of P. gingivalis, a suspected pathogen in adult chronic periodontitis.