Streptococci are gram positive and exhibit purple color cocci when gram stained and observed under the microscope. Gram-positive bacteria such as streptococci have a membrane that contains a thick layer of peptidoglycan. Peptidoglycan can retain the violet blue, and does not wash off with alcohol. It grows in short chains, containing several streptococci. It looks a lot like a string of beads. Blood agar test show that Strep!.
tococcus such as groups A, B, C, F and G are b- hemolytic, S. pneumoniae, a group D, which is also called Enterococcus, are a-hemolytic. Among all groups of Streptococci, group A and B are the most common and disease causing in human.
The most common form of Streptococcus is group A strep. Group A Streptococcus has a group-specific polysaccharide antigen ("C- substance) with a type-specific protein antigen ("M- protein)(2-pp63). It is also called S. pyogenes. As its name indicates, it is a pus forming bacteria. Pus is formed when the bacteria lyses the red blood cells, and this process results in a thick yellowish fluid that is a significant sign of strep infection. The most common form of group A strep infection is pharyngitis, better known as "strep throat."" "Sore throat appears to be a bad indicator of Streptococcus pharyngitis in the general population-(3-pp231). It causes the inflammation and swelling of throat and tonsils. If not treated properly, it can spread to the respiratory tract and into the lung where it can develop into pneumonia. It often spreads through direct contact. It is more common in schools where children share toys and food. Many other diseases can developed from group A strep infections, such as skin condition called impetigo followed by a kidney condition called glomerulonephritis. In its worst case, group A strep can cause a deadly disease. If ignored on its first signs of infection, it becomes more virulent and spreads to deeper tissues of the body.