Rapid detection of S. mutans surface antigen I/II using a sensitive monoclonal anti-Ag I/II antibody by ELISA

The Identification of Oral Cariogenic Bacteria through Colorimetric Sensor Array Based on Single-Atom Nanozymes

Effective identification of multiple cariogenic bacteria in saliva samples is important for oral disease prevention and treatment. Here, a simple colorimetric sensor array is developed for the identification of cariogenic bacteria using single-atom nanozymes (SANs) assisted by machine learning. Interestingly, cariogenic bacteria can increase oxidase-like activity of iron (Fe)─nitrogen (N)─carbon (C) SANs by accelerating electron transfer, and inversely reduce the activity of Fe─N─C further reconstruction with urea. Through machine-learning-assisted sensor array, colorimetric responses are developed as "fingerprints" of cariogenic bacteria. Multiple cariogenic bacteria can be well distinguished by linear discriminant analysis and bacteria at different genera can also be distinguished by hierarchical cluster analysis. Furthermore, colorimetric sensor array has demonstrated excellent performance for the identification of mixed cariogenic bacteria in artificial saliva samples. In view of convenience, precise, and high-throughput discrimination, the developed colorimetric sensor array based on SANs assisted by machine learning, has great potential for the identification of oral cariogenic bacteria so as to serve for oral disease prevention and treatment.

Sophoraflavanone G prevents Streptococcus mutans surface antigen I/II-induced production of NO and PGE2 by inhibiting MAPK-mediated pathways in RAW 264.7 macrophages

BACKGROUND

Sophora flavescens AITON (Leguminosae) is a typical traditional Korean medical herb considered to exhibit antibacterial, anti-inflammatory, and antipyretic effects, and is also used for the treatment of skin and mucosal ulcers, sores, diarrhea, gastrointestinal hemorrhage, arrhythmia, and eczema.

OBJECTIVE AND DESIGN

This study examined the inhibitory effects of sophoraflavanone G (SF) of S. flavescens on the bacterial fibrillar protein, Antigen I/II (AgI/II)-N recombinant protein isolated from Streptococcus mutans(rAg I/II)-induced production of nitric oxide (NO) and prostaglandin E2 (PGE2). The investigation was focused on whether SF could inhibit the production of proinflammatory mediators such as nitric oxide (NO) and prostaglandin (PG) E2 as well as the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-a, interleukin (IL)-6, nuclear factor (NF)-κB and mitogen-activated protein kinases (MAPKs) in rAgI/II-stimulated RAW 264.7 cells using Griess reagent, Enzyme linked immunosorbent assay (ELISA), and Western blotting analysis.

RESULTS

SG significantly inhibited the production of NO and PGE2 and pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor α in Ag I/II-N-stimulated RAW264.7 cells, which were mediated by the down-regulation of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. The SF inhibited the phosphorylation of IκB-α, nuclear translocation of p65, and subsequent activation of NF- κB in the rAgI/II-stimulated cells. In addition, the SF suppressed the rAgI/II-stimulated activation of ERK MAPK as well as the MAPK inhibitor significantly reduced the rAgI/II-induced production of NO and PGE2.

CONCLUSION

Collectively, we suggest that the SF inhibits the expression and production of inflammatory mediators by blocking the ERK MAPK mediated pathway and inhibiting the activation of NF-κB.

Effects of combined oleic acid and fluoride at sub-MIC levels on EPS formation and viability of Streptococcus mutans UA159 biofilms

Despite the widespread use of fluoride, dental caries, a biofilm-related disease, remains an important health problem. This study investigated whether oleic acid, a monounsaturated fatty acid, can enhance the effect of fluoride on extracellular polysaccharide (EPS) formation by Streptococcus mutans UA159 biofilms at sub-minimum inhibitory concentration levels, via microbiological and biochemical methods, confocal fluorescence microscopy, and real-time PCR. The combination of oleic acid with fluoride inhibited EPS formation more strongly than did fluoride or oleic acid alone. The superior inhibition of EPS formation was due to the combination of the inhibitory effects of oleic acid and fluoride against glucosyltransferases (GTFs) and GTF-related gene (gtfB, gtfC, and gtfD) expression, respectively. In addition, the combination of oleic acid with fluoride altered the bacterial biovolume of the biofilms without bactericidal activity. These results suggest that oleic acid may be useful for enhancing fluoride inhibition of EPS formation by S. mutans biofilms, without killing the bacterium.

Rapid fluorescent detection of Escherichia coli K88 based on DNA aptamer library as direct and specific reporter combined with immuno-magnetic separation

Nucleic acid aptamers have long demonstrated the capacity to bind cells with high affinity so that they have been utilized to diagnose various important pathogens. In this study, a DNA aptamer library was on initial efforts developed to act as a specific reporter for rapid detection of enter toxigenic Escherichia coli (ETEC) K88 combined with immuno-magnetic separation (IMS). During a Whole-cell Systematic Evolution of Ligands by Exponential Enrichment (CELL-SELEX) procedure, the last selection pool against ETEC K88, which is named "DNA aptamer library" here, was selected and subsequently identified by flow cytometric analysis and confocal imaging. A K88 monoclonal antibody (mAb) with high affinity (K(aff): 1.616 ± 0.033 × 10(8) M(-1)) against K88 fimbrial protein was prepared, biotinylated and conjugated to streptavidin-coated magnetic beads (MBs). After the bacteria were effectively captured and enriched from the complex sample by immuno-magnetic beads (IMBs), 5'-FITC modified aptamer library was directly bound to target cells as a specific reporter for its detection. The detection system showed clearly high specificity and sensitivity with the detection limit of 1.1 × 10(3) CFU/ml in pure culture and 2.2 × 10(3) CFU/g in artificially contaminated fecal sample. The results also indicated that fluorophore-lablled DNA aptamer library as specific reporter could generate more reliable signals than individual aptamer with best affinity against target cells and implied it would have great applied potential in directly reporting bacteria from complex samples combined with IMS technology.