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Herein, positively surface-charged silver nanoparticles (AgNPs) capped with trimethylchitosan nitrate (TMCN) were synthesized using an environmentally friendly method. Nano-sized TMCN-AgNPs (~80 nm) with high zeta potential (>30 mV) provide sufficient static repulsion to stabilize colloid AgNPs in aqueous solutions without aggregation for >3 months. In in vitro cell cycle assays, TMCN-AgNPs showed low cytotoxicity towards L929 cells. A microdilution inhibition assay demonstrated the antifungal potential of TMCN-AgNPs, with a minimum inhibitory concentration of 0.06 mM against Candida tropicalis ATCC 750, and 0.46 mM against both Candida albicans ATCC 76615 and Candida glabrata ATCC 15545. Moreover, the addition of TMCN-AgNPs at 0.23 mM significantly reduced biofilm formation in 96-well plates with C. albicans and C. tropicalis. Importantly, when zebrafish eggs were infected with Candida cells, 0.23 mM TMCN-AgNPs greatly diminished the amount of biofilm on eggs and rescued the survival of embryos by up to 70%.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a rapid and accurate method to identify microorganisms in clinical laboratories. This study isolates yeast-like microorganisms in the oral washes that are collected from non-bedridden nursing home residents, using CHROMagar Candida plates, and identifies them using Bruker MALDI-TOF MS. The ribosomal DNA sequences of the isolates are then examined. Three hundred and twenty yeast isolates are isolated from the oral washes. Candida species form the majority (78.1%), followed by Trichosporon/Cutaneotrichosporon species (8.8%). Bruker MALDI-TOF MS gives a high-level confidence, with a log(score) value of &ge, 1.8, and identifies 96.9% of the isolates. There are six inconclusive results (1.9%), and those sequences are verified as rare clinical species, including Candida ethanolica, Cutaneotrichosporon jirovecii, Exophiala dermatitidis, and Fereydounia khargensis. Almost all of the isolates have a regular color on the CHROMagar Candida plates. If the colonies are grouped by color on the plates, a specific dominant yeast species is present in each color group, except for purple or orange isolates. In conclusion, MALDI-TOF MS is verified as a fast, accurate and practical method to analyze oral yeasts in elderly subjects.