Re: how do bacteria cause strep throat in humans?

Strep throat is caused by a certain strain of bacteria called beta-
hemolytic, Group A Streptococcus pyogenes.  These bacteria normal 
inhabitants of our mouths and throat.  These bacteria usually do not cause 
any problems because their numbers may be limited by competition with 
other microbes and reaction with our non-specific host defenses / immunity.

However, conditions may arise that change the normal environment in our 
mouths and throats.  These conditions can include: viral infections, 
stress, or other medical conditions that change the mix of our normal 
flora.  These changes may allow the number of these strep bacteria to 
increase.

As the number of these microbes increase, the actual sore throat or 
pharyngitis is due to proteins produced by the bacteria that damage local 
cells and cause the host to respond with an inflammatory response.

Routinely, confirmed cases of strep throat are treated with antibiotics.