An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. The main classes of antimicrobial agents are disinfectants nonselective antimicrobials such as bleach, which kill a wide range of microbes on non-living surfaces to prevent the spread of illness, antiseptics which are applied to living tissue and help reduce infection during surgery and antibiotics which destroy microorganisms within the body. The term antibiotic originally described only those formulations derived from living micro organisms but is now also applied to synthetic antimicrobials, such as the sulphonamides, or fluoroquinolones.