[Study on inhibitory effect of Ag⁺-loaded TiO₂ on the biofilm of Staphylococcus aureus]

To observe the antibacterial effect of Ag⁺-loaded TiO₂ (Ag-TiO₂) and Ag-TiO₂ coated endotracheal tube (ETT) on the bacterial biofilm (BF) of Staphylococcus aureus.

2, 3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) colorimetric method was used to detect minimal inhibitory concertation (MIC) of Ag-TiO₂ for inhibition of BF of Staphylococcus aureus. The Ag-TiO₂ coated ETT were prepared, and divided into 11 mg/L, 8 mg/L, 5 mg/L, 2 mg/L and 0 mg/L ETT group, according to the concentration gradient, then impregnated in the liquid with Staphylococcus aureus at a concentration of 1.0×10⁹ cfu/L. The influence of antibacterial coated ETT on the formation of Staphylococcus aureus BF was determined by detecting the colonies of bacteria and BF on the ETT.

Ag-TiO₂ had a significant inhibitory effect on Staphylococcus aureus BF in a concentration-dependent manner, and its MIC was 10 mg/L. Ag-TiO₂ coated ETT has significant anti-Staphylococcus aureus BF effect, and the higher the concentration, the stronger the effect. The absorbance (A) values of Ag-TiO₂ 5 mg/L, 8 mg/L, 11 mg/L ETT groups were significantly lower than that in control group (0.176±0.004, 0.147±0.002, 0.094±0.002 vs. 0.267±0.045, all P < 0.05). The inhibitory rates of Ag-TiO₂ 2 mg/L, 5 mg/L, 8 mg/L ETT groups were increased gradually, and 11 mg/L Ag-TiO₂ coated ETT group had the highest inhibitory rate for BF, the inhibitory rates were 6.4%, 34.1%, 44.9% and 64.8%, respectively.

Both Ag-TiO₂ and Ag-TiO₂ coated ETT have significant inhibitory effects on Staphylococcus aureus BF.