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
Exogenous bacteria of this concept is "bacterial flora," which consists of exogenous bacteria ingested and endogenously colonized during the early stages of life. Bacteria that are part of normal internal ecosystems, also known as bacterial flora, are called "Endogenous Bacteria". A significant amount of prominent diseases are induced by "exogenous bacteria" such as "gonorrhea", "meningitis", "tetanus", and "syphilis." Pathogenic exogenous bacteria can enter a host via cutaneous transmission, inhalation, and consumption. Only a minority of bacteria species cause disease in humans; and many species colonize in the human body to create an ecosystem known as bacterial flora. Bacterial flora is endogenous bacteria,