Fimbria-mediated coaggregation between human oral anaerobes Treponema medium and Porphyromonas gingivalis.

Bacterial binding phenomena among different bacterial genera or species play an important role in bacterial colonization in a mixed microbiota such as in the human oral cavity. The coaggregation reaction between two gram-negative anaerobes, Treponema medium and Porphyromonas gingivalis, was characterized using fimbria-deficient mutants of P. gingivalis and specific antisera against purified fimbriae and bacterial whole cells. T. medium ATCC 700273 strongly coaggregated with fimbriate P. gingivalis strains ATCC 33277 and 381, but not with afimbriate strains including transposon-induced fimbria-deficient mutants and KDP98 as a fimA-disrupted mutant of P. gingivalis ATCC 33277. In the P. gingivalis-T. medium coaggregation assay, the presence of rabbit antiserum against the purified fimbriae or the whole cells of P. gingivalis ATCC 33277 produced different "aggregates" consisting predominantly of P. gingivalis cells with few spirochetes, but both preimmune serum and the antiserum against the afimbriate KDP98 cells did not inhibit the coaggregation reaction. Heated P. gingivalis cells lost their ability to bind both heated and unheated T. medium cells. This T. medium-P. gingivalis coaggregation reaction was inhibited by a cysteine proteinase inhibitor, leupeptin, and also by arginine and lysine, but not by EDTA or sugars including lactose. A binding assay on nitrocellulose membranes and immunoelectron microscopy demonstrated that a heat-stable 37 kDa surface protein on the T. medium cell attached to the P. gingivalis fimbriae.

Nanoscale analysis of pharmacologically active catechins in body fluids by HPLC using borate complex extraction pretreatment.

A pretreatment method based on borate complex formation is described for the selective and simultaneous quantitation of pharmacologically active catechins in human plasma and saliva. This method is based on the interaction of catechins with diphenylborate (as a complexing agent) and tetra-n-butylammonium (as a counter ion) in alkaline media to give the catechin-diphenylborate complex and ion-pair that are extractable to the organic phase. The complex extracted in an organic solvent is dissociated by shaking with an aqueous trifluoroacetic acid solution to back-extract free catechins to the aqueous phase, followed by high-performance liquid chromatography (HPLC) analysis with fluorometric and diode array detection. Under optimal conditions, all catechins originating from green tea extracts were selectively purified from plasma and saliva samples, and they were stabilized during the extraction procedures by forming the complex. The nano-scale quantitative analysis of eight catechins was achieved with high recovery and analytical reproducibility. The proposed method would be a useful tool for pharmacokinetic studies of catechins in plasma and saliva.

Antibacterial activity of hydroxychalcone against methicillin-resistant Staphylococcus aureus.

Anti-candidal hydroxychalcone, 2,4,2'-trihydroxy-5'-methylchalcone (THMC), was investigated for its antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). THMC showed the minimum inhibitory concentrations of 25.0-50.0 mug/ml against tested 20 strains, at which the effect was based on a bacteriostatic action. THMC of 25.0 mug/ml completely inhibited the incorporation of radio-labelled thymidine and uridine into MRSA cells. In combination with antibiotics, the fractional inhibitory concentration indices were 0.47 for gentamicin and 0.79 for vancomycin, indicating that THMC acts synergistically with these agents. THMC would be a potent therapeutic agent for MRSA infections.