Streptococcus mutans is one of the bacteria that initiates the colonization of the pellicle at the tooth surface. It forms a plaque, together with other bacteria, which gradually dissolves the pellicle and leaves the tooth surface unprotected against the acidic oral environment. Calcium phosphate ceramics are excellent synthetic materials for the study of biofilm formation in dentistry because they are comparable to teeth in chemical composition and structure. Calcium phosphates can be processed to achieve a variety of crystalline compounds with biologically relevant ionic substitutions and structures that allow study of the effect of the surface chemistry and the topography independently. In this article, we describe the preparation and characterization of three types of calcium phosphate-based materials as a suitable surface for the formation of the S. mutans biofilm: beta-tricalcium phosphate (β-TCP); sintered hydroxyapatite (SHA); and calcium-deficient hydroxyapatite (CDHA). The densest biofilms were formed on the surfaces of SHA and CDHA, with no significant differences due to the stoichiometry or microstructure. In contrast, β-TCP showed a lower susceptibility to S. mutans biofilm formation, suggesting that the crystalline structure is the controlling parameter. Subsequently, SHA was selected to develop a dental biofilm model that allowed study of S. mutans biofilm susceptibility to chlorhexidine and ethanol.
An increasing microbial resistance to known antibiotics raises a demand for new antimicrobials. In this study the antimicrobial properties of a series of new N-Alkylpyridinium quaternary ammonium compounds (QACs) with varying alkyl chain lengths were evaluated for several nosocomial pathogens. The chemical identities of the new QACs were determined by NMR, LC-MS, and HRMS. All the planktonic bacteria tested were susceptible to the new QACs as evaluated by MIC and MBC assays. The antimicrobial effect was most pronounced against Staphylococcus aureus clinical isolates. Live/dead staining CLSM was used to test the effectiveness of the QACs in biofilms. The effectiveness was up to 10-fold lower than in the plankton. When QACs were used as irrigants in Er:YAG - SSP photoacoustic steaming, their effectiveness significantly increased. The combined use of irrigants and photoacoustic streaming increased biofilm removal from the surface and increased the killing rate of the cells remaining on the surface. This may allow for a shorter chemical exposure time and lower dosage of QACs used in applications. The results demonstrate that the new QACs have potential to be applied as antibacterial compounds effective against planktonic and biofilm bacteria as well as irrigants in removal of difficult-to-reach biofilms.
- Publikační typ
- časopisecké články MeSH
Growing evidence of antibiotic-resistant pathogens is a serious medical issue that has to be addressed. Our antimicrobial research is focused on searching for novel small molecules that differ from the most clinically used antibiotics by chemical structure and mechanism. However, this fundamental research is like looking for a needle in a haystack. In addition, in vitro methods are time-consuming and expensive to screen large number of compounds in reasonable time. Off-target screening can represent a solution to find novel and effective antimicrobial agents that can eliminate these problems. Accordingly, molecular docking in the family of selected frentizole derivatives predicted their potential to inhibit bacterial nicotinate mononucleotide adenylyltransferase (NadD). This bacterial-essential specific enzyme has an important role in NAD metabolism. Thus, underlying mechanism of antimicrobials derived from frentizole would be interference with this biochemical process. Unfortunately, broth microdilution assay did not display any antimicrobial activity of tested compounds. On the other hand, herein we propose that off-target screening can facilitate searching for new drugs and that NadD could be a relevant target for antimicrobials.
- MeSH
- antiinfekční látky * chemie MeSH
- Bacteria MeSH
- benzothiazoly chemie MeSH
- indikátorové diluční techniky MeSH
- inhibitory enzymů chemie MeSH
- lidé MeSH
- nikotinamidnukleotidadenylyltransferasa * antagonisté a inhibitory MeSH
- simulace molekulového dockingu MeSH
- techniky in vitro MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
