Titanate-Metal Complex as a Novel Antimicrobial in Dentistry

Abstract

Lactobacillus casei adhesion of cariogenic bacteria metal-titanate A B S T R A C TMetal-titanates possess antimicrobial properties, and our previous studies showed that they could be beneficial in reducing bacterial load in dental materials and treatments. We investigated the mechanism of the antibiotic effect of Au(III)-monosodium titanate (MST) complex on known cariogenic bacteria, Streptococcus mutans and Lactobacillus casei. Bacteria were exposed sequentially to 10, 25, 50, 100, 200, and 400 mg/L of Au(III)-MST to determine their ability to develop resistance. Cells were grown for 4 and 18 hours following exposure to Au(III)-MST, and changes in adhesion gene expression were assessed by quantitative real-time PCR. Bacterial adhesion was assessed using Syto 13 dye and polystyrene plates.Bacterial counts were determined using OD reading. Expression of genes srtA and fbpA in L. casei was initially decreased after 4 hours of exposure. Expression of the Pac gene in the S. mutans culture was increased after 18 hours. The resistance study showed that the growth of L. casei in the presence of the metal complex was steadily decreased compared to the control, whereas growth of S. mutans was similar to the control up until 200 mg/L but significantly impaired in the presence of 400 mg/L Au(III)-MST. L. casei did not exhibit resistance to the Au(III)-MST complex, whereas S. mutans was able to grow in the presence of up to 200 mg/L Au(III)-MST. The mechanism underlying the antimicrobial effect of Au(III)-MST on L.casei may be via the regulation of srtA1 and fbpA genes and on S. mutans may be via the regulation of the Pac gene.