The primary cause of periodontitis is plaque-associated anaerobic gram-negative bacteria. As shown in the patients with defects in the number or function of neutrophils, innate immunity plays an important role in resistance to bacterial infection and periodontitis. Toll-like receptor 4(TLR4) is one of the key receptors that recognize the molecular patterns of microbes and initiate innate immune response. To understand the role of TLR4 in the pathogenesis of periodontitis, we investigated whether Asp299Gly of TLR4 mutation is associated with periodontitis in Korean population. Subjects for this study included 90 healthy subjects and 98 periodontitis patients. The Asp299Gly mutation was screened by PCR-Restriction Fragment Length Polymorphism(RFLP) of genomic DNA from blood cells using a primer that creates a NcoI restriction site only in the mutant allele. The Asp299Gly mutation was not found in all subjects tested. Our results suggest that the Asp299Gly mutation of TLR4 is very rare in a Korean population. Further mutation screening may be required to determine the role of TLR4 in the pathogenesis of periodontitis.
Mitis-salivarius sucrose bacitracin(MSB) medium is widely used in the selective isolation of mutans streptococci(MS), a designation for a group of oral cariogenic species. Recently, we have isolated three bacterial strains grown on MSB agar from human dental plaques. The three strains exhibited biochemical characteristics similar to those of the biotype IV of MS, with the exception that they manifested a positive reaction for arginine deaminase. The objective of this study was to identify and characterize these three clinical isolates. The bacteria were identified with biochemical tests as well as by 16S rDNA cloning and sequencing. In order to compare the antibiotics susceptibility of the clinical isolates with that of type strain, the minimum inhibitory concentrations of 9 antibiotics were determined using broth dilution assays. The results identified all of our three clinical isolates as Enterococcus faecalis. All E. faecalis strains were found to be susceptible to penicillin G, amoxicillin, augmentin, and vancomycin, but were resistant to ciprofloxacin, cefuroxim axetil, and clindamycin. Our findings indicate that E. faecalis is capable of growing on MSB agar, and suggest that the MSB medium be improved so that only MS should be recoverable on the medium, as originally devised for their selection.
This study was undertaken to develop PCR primers for the identification and detection of Streptococcus anginosus using species-specific forward and reverse primers. These primers targeted the variable regions of the 16S ribosomal RNA coding gene(rDNA). The primer specificity was tested against 12 S. anginosus strains and 6 different species(10 strains) of oral bacteria. The primer sensitivity was determined by testing serial dilutions of the purified genomic DNA of S. anginosus ATCC 33397T. The data showed that species-specific amplicons were obtained from all the S. anginosus strains tested, but not in the six other species. The PCR could detect as little as 0.4pg of the chromosomal DNA from S. anginosus. This suggests that the PCR primers are highly sensitive and applicable to the detection and identification of S. anginosus.
Concerns remain regarding the biocompatibility and adverse effects of dental casting alloys. The aim of this study was to understand the cytopathogenic effect of metal ions, which might be released from dental alloys, on oral squamous carcinoma(OSC) cells. The cellular morphology, viability, the type of cell death and molecular change in response to metal ion salt solutions including aluminum(Al), cobalt(Co), copper(Cu) and nickel(Ni) were examined. The values for the metal ions with the exception of AI were estimated to be between 400 and 600μM. The cells treated with the metal ions showed apoptotic change with the exception of Al ions. Metal ion-induced apoptosis was further confirmed using flow cytometric analysis. This study showed that the cytotoxicity and the mode of cell death by metal ions clearly depend on the cell type, the type of metal ion and the duration of exposure. The protein level of Rb, a tumor suppressor that affects apoptosis para-doxically, was higher in the cells treated with Co, Cu and Ni. It is believed that apoptosis and cell damage in the OSC cells treated with Co, Cu or Ni can be evoked by the regulation of Rb.
Periodontopathogens including Porphyromonas gingivalis interact with host periodontal cells and the excessive subsequent host responses contribute a major part to the development of periodontal diseases. Cyclooxygenase(COX)-2-synthesized has detrimental activities in terms of periodontal pathogenesis. The present study investigated induction of COX-2 expression by P. gingivalis in human monocytic THP-1 cells. Live P. gingivalis increased expression of COX-2, but not that of COX-1, which was demonstrated at both mRNA and protein levels. Elevated levels of were released from P. gingivalis-infected THP-1 cells. Pharma-cological inhibition of p38 mitogen-activated protein kinase(MAPK) and extracellular signal-regulated kinase(ERK) substantially attenuated P. gingivalis-induced COX-2 mRNA expression. Indeed, activation of p38 MAPK and ERK was observed in P. gingivalis-infected THP-1 cells. Also, P. gingivalis induced activation of nuclear factor-κB (NF-κB)which is an important transcription factor for COX-2. These results suggest that COX-2 expression is up regulated in P. gingivalis-infected monocytic cells, at least in part, via p38 MAPK, ERK, and NF-κB.