Modulation of Porphyromonas gingivalis proteinase activity by suboptimal doses of antimicrobial agents.
BACKGROUND
Antimicrobial agents are sometimes used as adjuncts for the treatment of aggressive and refractory forms of periodontitis. In this study, we used a culture plate assay to investigate the effect of suboptimal doses of antimicrobial agents on proteinase activity of Porphyromonas gingivalis.


METHODS
A culture plate assay using gelatin as the substrate, which allows a semiquantitative determination of proteinase activity, was developed. Suboptimal inhibitory concentrations of tetracycline, minocycline, doxycycline, metronidazole, penicillin G, or chlorhexidine were added to the medium, and proteolysis zones were determined following the growth of three strains of P. gingivalis. The effect of antimicrobials on outer membrane vesicle-associated gingipains also was determined.


RESULTS
The gelatin plate assay was a convenient, simple procedure for investigating the effect of suboptimal inhibitory concentrations of antimicrobial agents on proteinases produced by P. gingivalis. The largest reduction (> 75%) in the proteolysis zones produced by three strains of P. gingivalis was obtained with minocycline. Tetracycline and doxycycline also reduced the proteolysis zones. A suboptimal inhibitory concentration of chlorhexidine increased the proteolysis zones by up to 70%. Metronidazole and penicillin G produced no noticeable effect. The suboptimal inhibitory concentrations of minocycline, tetracycline, and doxycyline did not reduce the activity of outer membrane vesicle-associated Arg- and Lys-gingipains.


CONCLUSIONS
Results from this study suggest that sublethal concentrations of some antimicrobial agents in subgingival sites have the potential to affect the physiology of P. gingivalis, notably by increasing or decreasing the proteolytic activity of the bacteria.
Oral Ecology Research Group, Faculty of Dentistry, Université Laval, Quebec, Canada. Daniel.Grenier@greb.ulaval.ca
Daniel
D
Grenier
Elizabeth
E
Roy
Denis
D
Mayrand
D018829:Adhesins, Bacterial / Q000187:drug effects; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D000890:Anti-Infective Agents / Q000008:administration & dosage; D000891:Anti-Infective Agents, Local / Q000008:administration & dosage; D001425:Bacterial Outer Membrane Proteins / Q000037:antagonists & inhibitors; D002710:Chlorhexidine / Q000008:administration & dosage; D003546:Cysteine Endopeptidases / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000008:administration & dosage; D004318:Doxycycline / Q000008:administration & dosage; D010450:Endopeptidases / Q000187:drug effects*; D005780:Gelatin / Q000378:metabolism; D000080867:Gingipain Cysteine Endopeptidases; D006388:Hemagglutinins / Q000187:drug effects; D006801:Humans; D008795:Metronidazole / Q000008:administration & dosage; D008911:Minocycline / Q000008:administration & dosage; D010400:Penicillin G / Q000008:administration & dosage; D010518:Periodontitis / Q000382:microbiology; D016966:Porphyromonas gingivalis / Q000187:drug effects / Q000201:enzymology*; D011480:Protease Inhibitors / Q000008:administration & dosage*; D013752:Tetracycline / Q000008:administration & dosage
D018829:Adhesins, Bacterial; D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D000891:Anti-Infective Agents, Local; D001425:Bacterial Outer Membrane Proteins; D015853:Cysteine Proteinase Inhibitors; D000080867:Gingipain Cysteine Endopeptidases; D006388:Hemagglutinins; D011480:Protease Inhibitors; D008795:Metronidazole; D005780:Gelatin; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D013752:Tetracycline; D008911:Minocycline; D004318:Doxycycline; D010400:Penicillin G; D002710:Chlorhexidine