Communities of bacteria wrapped in self-generated extracellular polymeric matrix and attached to a solid surface are known as biofilm. Biofilm formation and development can be divided into three stages: adhesion of cells to a surface, reproduction of the cells, and dispersion of cells. The procedure, which surface-attached biofilm disperses bacterial cells into the environment to colonize new sites, is defined as biofilm dispersal. Biofilm dispersal is an essential stage of biofilm life cycle. It plays an important role in the transmission of bacteria. For many pathogenic bacteria, biofilm dispersal can transform bacteria in biofilm into planktonic state and promote the spread of infection. The formation of biofilm may increase the resistance of bacteria to antimicrobial agent and host defence response compared with planktonic cells. In the oral cavity, oral microorganism can attach to the surface of oral tissue and prosthesis to form biofilm. Dental caries and periodontal disease are oral chronic infections diseases of the oral tissue. The occurrence of them has a close relationship with biofilm. The mechanism of dispersal is a hot topic in recent years. Some agents which promote dispersal might be a therapeutic potential against biofilm infections. The clinical implication of dispersal agents and potential application are promising. This article reviews the dispersal-inducing agents of oral biofilms.
Bacteria ; Biofilms ; Dental Caries ; Humans

OBJECTIVETo compare the susceptibility of Porphyromonas gingivalis to metronidazole at different planktonic cell densities and in biofilm, and to evaluate the role of cell density in antibiotic drug resistance in Porphyromonas gingivalis biofilm.

METHODSThe minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of metronidazole against Porphyromonas gingivalis were detected by a broth dilution method under a final inocula of 10(6) CFU x mL(-1) and 10(9) CFU x mL(-1) (cell number equal to biofilm). After the initial biofilm formed in the microtiter plate wells, the MIC and MBC of metronidazole to the intact and succedent resuspended biofilm were determined.

RESULTSThe MIC and MBC of metronidazole against 10(6) CFU x mL(-1) planktonic Porphyromonas gingivalis were 0.063, 0.125 mg x L(-1) respectively. However, those against 10(9) CFU x mL(-1) planktonic Porphyromonas gingivalis were 25, 50 mg x L(-1). Against intact Porphyromonas gingivalis biofilm, the MIC was 25 mg x L(-1) and MBC was higher than 125 mg x L(-1), those against resuspended biofilm was 25, 125 mg x L(-1) respectively.

CONCLUSIONThe resistance of Porphyromonas gingivalis to metronidazole increases along with the augment of the bacterial density. Cell density plays an important role in the resistance of biofilm. However, extracellular matrix and the integrity of biofilm may be the other influence factors for the biofilm resistance.

Anti-Bacterial Agents ; Biofilms ; Cell Count ; Metronidazole ; Microbial Sensitivity Tests ; Porphyromonas gingivalis

OBJECTIVETo investigate the expression and the distribution of human beta defensin (hBD)-4 in healthy gingiva.

METHODSHealthy gingival specimens were collected. The expression of hBD-4 peptides in 18 gingival specimens were detected by immunohistochemistry. The hBD-4 mRNA were determined in freshly isolated gingival tissue by real time reverse transcription-polymerase chain reaction (real time RT-PCR) in 30 gingival specimens.

RESULTSIn 18 gingival specimens, hBD-4 peptides were expressed in 13 gingival specimens. In 30 gingival specimens, hBD-4 were detected in 4 gingival specimens by real time RT-PCR.

CONCLUSIONThe distribution and the expression levels of hBD-4 are different in healthy gingiva. This result may suggest that the hBD-4 play a role in maintaining the periodontal health.

Gingiva ; Humans ; RNA, Messenger ; beta-Defensins