Broad-spectrum antibiotic estimated 10-100 trillion multiple organisms that colonize the human body. As a side-effect of therapy, antibiotics can change the body's normal microbial content by attacking indiscriminately both the pathological and naturally occurring, beneficial or harmless bacteria found in the intestines, lungs and bladder. The destruction of the body's normal bacterial flora is thought to disrupt immunity, nutrition, and lead to a relative overgrowth in some bacteria or fungi. An overgrowth of drug-resistant microorganisms can lead to a secondary infection such as "Clostridium difficile" ("C. diff") or candidiasis ("thrush"). This side-effect is more likely with the use of broad-spectrum antibiotics, given
Social history of viruses are bacteria and archaea. Viruses are the main agents responsible for the rapid destruction of harmful algal blooms, which often kill other marine life, and help maintain the ecological balance of different species of marine blue-green algae, and thus adequate oxygen production for life on Earth. The emergence of strains of bacteria that are resistant to a broad range of antibiotics has become a problem in the treatment of bacterial infections. Only two new classes of antibiotics have been developed in the past 30 years, and novel ways of combating bacterial infections are being sought. Bacteriophages were first used to