The use of Bacillus subtilis bacteria as a tool to assess the toxicity of pharmaceuticals in the environment

Abstract

Pharmaceuticals and personal care products are now known as microcontaminants due to their effects on bacterial resistance and effect on non-targeted organisms. Most recently, these substances have been found in surface water, sewage, hospital and care home wastewaters and landfill. Pharmaceuticals have been known to pose acute and chronic effects especially when exposed at higher concentrations and for longer durations. This study adopted the spectrophotometric method to assess the acute and chronic effects of seven pharmaceuticals on Bacillus subtilis bacteria. The effects were observed in terms of the conversion of 3-(4.5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt; (MTS) to a colored formazan product. The effect of pharmaceuticals was measured as a reduction of tetrazolium solution and expressed as percentage. The results indicate that both acute and chronic effects exist with Bezafibrate, Diclofenac, Diatrizoate, Ibuprofen and Atenolol inhibiting bacterial growth at 50 μg/ml. Consequently, at 500 μg/ml, all the pharmaceuticals inhibited growth thereby posing acute effects. In addition, all the eight pharmaceutical substances tested inhibited bacterial growth at 50 μg/ml and 500 μg/ml when exposed to pharmaceuticals for more than 24 h. The implication is that wastewater from hospitals can likely inhibit biological process of breaking waste in the wastewater treatment plants.