Impacts on antibiotic-resistant bacteria and their horizontal gene transfer by graphene-based TiO2&Ag composite photocatalysts under solar irradiation

In recent years, photocatalysis has been considered as a promising method, which provides measures to environmental pollution. Antibiotic resistant bacteria (ARB) and their antibiotic resistance genes (ARGs), as the emerging environmental pollutants, are released into the environment, resulting in antibiotic resistance spread. TiO2-based nanocomposites, as the most common photocatalytic material, may influence ARB and ARGs under photocatalytic conditions. However, the research on this aspect is rare. A novel nanocomposite synthesized from Ag, TiO2 and graphene oxide (GO), was selected as a representative of nanomaterials for investigation. The experimental results indicated that TiO2/Ag/GO nanocomposites significantly affected ARB vitality. 100 mg/L TiO2/Ag/GO will reduce bacterial survival to 12.2% in 10 min under simulated sunlight irradiation. Chloramphenicol as the most representative antibiotic in the water, reduces the effect of ARB inactivation under photocatalytic conditions. The addition of TiO2/Ag/GO could affect tetracycline antibiotic resistance. The level of bacterial tolerance to tetracycline had a significant reduction. The horizontal gene transfer was promoted from 1 to 2 folds with the addition of TiO2/Ag/GO. Even high TiO2/Ag/GO concentration (100 mg/L) sample had a limited promotion, suggesting that TiO2/Ag/GO will not increase the risk of antibiotic resistance spread compared to other nano materials.