Streptococcal Infections
Streptococcal infections are caused by species of the gram-positive cocci Streptococcus (streptococci).
The various disease-causing forms of streptococci are divided into groups based on their behavior, chemistry, and appearance. Each group tends to produce specific kinds of infections and symptoms. Many forms of streptococci live harmlessly in and on the body. Sometimes, even disease-causing streptococci can be found in healthy people (carrier state). When the laboratory finds these bacteria in sick people, it can be difficult to tell whether they are the cause of illness or not.
Infections with certain types of streptococci can cause an autoimmune reaction in which the body attacks its own tissues (see Section 16, Chapter 186). Autoimmune reactions can develop after an infection such as strep throat and may lead to rheumatic fever and kidney damage (glomerulonephritis).
Symptoms
Streptococci typically infect the throat and skin, although many other parts of the body can become infected, particularly the heart (endocarditis). Skin infections include cellulitis, erysipelas, impetigo, and necrotizing fasciitis (see Section 18, Chapter 211).
Strep throat is the most common streptococcal infection. Symptoms appear suddenly and include sore throat, sometimes with chills, fever, headache, nausea, vomiting, a rapid heartbeat, and a general feeling of illness (malaise). The throat is beefy red, the tonsils are swollen, and the lymph nodes in the neck may be enlarged and tender. Cough, inflammation of the larynx (laryngitis), and a stuffy nose are uncommon in streptococcal infections; these symptoms suggest another cause, such as a cold or allergy. However, in children younger than 4 years, the only symptom may be a runny nose.
Scarlet fever results when streptococci infecting a person--usually in the throat--release a toxin. This toxin leads to a widespread, pink-red rash that is most obvious on the abdomen, on the sides of the chest, and in the skinfolds. The rash does not itch or hurt. Other symptoms include a pale area around the mouth, a flushed face, and dark red lines in the skinfolds. Also, the tongue develops a white coating with red spots (white-strawberry tongue). After several days, the coating disappears and the tongue turns beefy red. The outer layer of reddened skin often peels after the fever subsides.
Diagnosis
Because of their characteristic symptoms, some streptococcal infections (such as cellulitis and impetigo) can usually be diagnosed without any tests. Other streptococcal infections, strep throat in particular, resemble illnesses caused by other bacteria and viruses. For these conditions, doctors try to confirm the diagnosis by obtaining a sample from the infected area for culture. Unfortunately, many infections (especially skin infections) are difficult to culture. Many bacteria live on or in the skin, so finding them in culture does not mean that they are the cause of the infection. Also, cultures must be allowed to grow overnight, so results are not immediately available. Certain rapid tests for streptococci produce results within a few hours. If the result of a rapid test is positive, a culture is not needed. However, if the rapid test is negative, most doctors recommend doing the overnight culture as well. These tests are important because most sore throats, even ones that look very bad, are caused by viruses and should not be treated with antibiotics.
Treatment
People with strep throat and scarlet fever usually get better in 2 weeks, even without treatment. Nevertheless, antibiotics can shorten the duration of symptoms and help prevent serious complications (such as rheumatic fever). Antibiotics also help prevent the spread of the infection to the middle ear, sinuses, and mastoid bone as well as to other people. An antibiotic, usually oral penicillin V, is started promptly after the appearance of symptoms and continued for 10 days.
Other streptococcal infections (such as cellulitis, necrotizing fasciitis, and endocarditis) are very serious and require intravenous penicillin, sometimes together with other antibiotics. In necrotizing fasciitis, surgical removal of dead, infected tissue is essential. Penicillin is effective against most streptococci, but some are resistant to penicillin and many other antibiotics.
Fever, headache, and sore throat can be treated with drugs (such as acetaminophen or nonsteroidal anti-inflammatory drugs [NSAIDs]) that reduce pain and fever. Neither bed rest nor isolation is necessary. However, family members or friends who have similar symptoms or who have had complications from earlier streptococcal infections may be given preventive therapy.
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