Sulfamethoxazole. Computer-generated molecular model of sulfamethoxazole (molecular formula: C10.H11.N3.O3.S), part of the sulphonamide group of antibiotics. It is composed of carbon (green), hydrogen (white), sulphur (red), nitrogen (blue) and oxygen (purple). Sulfamethoxazole works by inhibiting the synthesis of folic acid (folate) inside the bacterial cell. Folic acid is necessary for the production of genetic material (deoxyribonucleic acid, DNA). Without DNA, the bacteria cannot reproduce and the infection is stopped (bacteriostatic effect). Sulfamethoxazole's efficiency is being affected by the increase in bacterial resistance.