Antibiotics Antibiotics medicines are also as called antibacterials, it is a type of antimicrobial drug which is used in the treatment and prevention of bacterial infections. They will either kill or inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal activity. Antibiotic medicines are not effective against viruses such as the common cold or influenza; drugs which inhibit viruses are termed antiviral drugs or antivirals rather than antibiotics. Sometimes the term antibiotic is used to refer to any other substance which is used against microbes,synonymous with antimicrobial.Some sources distinguish between antibacterial and antibiotic;antibacterials are used in soaps and disinfectants, while antibiotics are used as medicine. Antibiotics are used to treat or prevent bacterial infections,and sometimes protozoan infections. (Metronidazole is effective against a number of parasitic diseases). When an infection is suspected of being responsible for an illness but the responsible pathogen has not been identified, an empiric therapy is adopted.This involves the administration of a broad-spectrum that is based on antibiotic signs and symptoms which are presented and initiated pending laboratory results however, it can take several days.