Is streptococcus a resident biota of the gastrointestinal tract?

Answer 1

It depends on the species. For example, Streptococcus bovis is usually found in the large bowel and it causes infectious endocarditis in people who have some diseases in that organ and have some cardiac abnormality. As for Streptococcus pyogenes, it can be found in the pharynx (throat) of some people as colonizing bacteria, and in others cause disease (amygdalitis), but it's not supposed to be found in most people. Streptococcus pneumoniae, which is the most common cause of pneumonia, sinusitis and otitis media, colonises a large number of infants, and can also cause disease if the conditions are favourable. Streptococcus viridans causes teeth disease and is part of the permanent micro-biota of the mouth; if imbalance occurs, then it can cause some problem. Enterococcus are a group of bacteria that also belongs to the major group of streptococcus, and, as the name says, are found in the large bowel, rarely being a cause of infectious endocarditis or urinary infection (of the bladder).