27 Apr


Bacteria of the genus streptococci differ from staphylococci for two main reasons:  they lack the enzyme catalase and they occur in chains rather than in clusters.  Catalase degrades hydrogen peroxide into water and oxygen.  The streptococci often times cause mixed infections with staphylococci but they independently can cause diseases such as pneumonia, meningitis, endocarditis, pharyngitis, erysipelas, and glomerulonephritis.  Streptococci occur naturally in the pharynx and mouth where they are found on the sufraces of teeth, tongue, cheek, throat, and in saliva.  The streptococci of the greatest importance to humans are S. pyogenes, S. agalactiae, and S. pneumoniae.  Several systems have been used to classify the streptococci.  One of the first was proposed by J. H. Brown in 1919 that was based on the ability of these bacteria to cause lysis of red blodd cells when grown on blood agar.