Disease Producing Bacteria
Some common gram positive bacteria which affect our health can be found in the Streptococcus group. Streptococci cause conditions such as Strep throat, middle ear infections and rheumatic fever, to name a few. Varieties of Streptococci are distinguished by their interaction with blood agar. Some varieties cause hemolysis of the red blood cells, resulting in a clear area around the colonies. These are beta strep variety. An example of a beta strep is Streptococcus A, which is commonly found in strep throat.
Streptococcus pneumonia is a bacteria which causes pneumonia. It's reaction with blood agar differs from the hemolytic action of group A. Strep pneumonia causes a greenish area around the colonies on a blood agar plate. The greenish tinge is due to the peroxidase present in Streptococcus pneumonia, which oxidizes red blood cells around the colony.
Another common gram positive bacteria is Staphylococcus epidermidis. This bacteria is quite prolific on the skin and generally does not cause harm, except when a person is immunocompromised. Another variety, Staph aureus, causes acne and, if it gets under the skin, can result in the formation of an abcess. Because of treatment with antibiotics over the years, Staphylococcus aureus has modified itself genetically to be resistant to antibiotics. It is often acquired in hospitals and is one of the most predominant noscomial infections. This variation is known as MRSA, methicillin-resistant Staphylococcus aureus.