Effects of antibiotic use
Altering the numbers of gut bacteria, for example by taking broad-spectrum antibiotics, may affect the host's health and ability to digest food. People may take the drugs to cure bacterial illnesses or may unintentionally consume significant amounts of antibiotics by eating the meat of animals to which they were fed. Antibiotics can cause antibiotic-associated diarrhea (AAD) by irritating the bowel directly, changing the levels of gut flora, or allowing pathogenic bacteria to grow. Another harmful effect of antibiotics is the increase in numbers of antibiotic-resistant bacteria found after their use, which, when they invade the host, cause illnesses that are difficult to treat with antibiotics.Changing the numbers and species of gut flora can reduce the body's ability to ferment carbohydrates and metabolize bile acids and may cause diarrhea. Carbohydrates that are not broken down may absorb too much water and cause runny stools, or lack of SCFAs produced by gut flora could cause the diarrhea.
A reduction in levels of native bacterial species also disrupts their ability to inhibit the growth of harmful species such as ''C. difficile'' and ''Salmonella kedougou'', and these species can get out of hand, though their overgrowth may be incidental and not be the true cause of diarrhea.
Gut flora composition also changes in severe illnesses, due not only to antibiotic use but also to such factors as ischemia of the gut, failure to eat, and immune compromise. Negative effects from this have led to interest in selective digestive tract decontamination (SDD), a treatment to kill only pathogenic bacteria and allow the reestablishment of healthy ones.
Pharmabiotics
Pharmabiotics is a generic term to encompass any form of therapeutic exploitation of the commensal flora, including the use of live probiotic bacteria, probiotic-derived biologically active metabolites, prebiotics, synbiotics or genetically modified commensal bacteria. Since the lack of gut flora can have such harmful health effects, the use of probiotics has anti-inflammatory effects in the gut and may be useful for improving health. Prebiotics are dietary components that can help foster the growth of microorganisms in the gut, which may lead to better health. There is evidence supporting a therapeutic role for probiotic strategies for treating mucosal inflammatory disorders such as IBD, atopy, infection, diarrhoea, cancer and arthritis.Adapted from the Wikipedia article Gut flora, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki
