Pharyngitis

Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Determining the causative agent based on symptoms alone is difficult. Thus, a throat swab is often performed to rule out a bacterial cause. The mainstay of treatment is symptomatic and supportive, with bacterial causes requiring antibiotics.

Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci (e.g., S. mutans, S. mitis, and S. sanguinis). Streptococcal infections cause a wide array of clinical manifestations, including pharyngitis, pneumonia, skin and soft tissue infections, endocarditis, septicemia, meningitis, and streptococcal toxic shock syndrome. They are also responsible for the postinfectious syndromes of acute rheumatic fever and poststreptococcal glomerulonephritis. Most streptococci are sensitive to penicillin.