Infections of the throat, or pharyngitis, are the most common type of upper respiratory infection. Most cases of pharyngitis occur during the colder months and frequently are accompanied by other infections. The symptoms of throat infection overlap considerably, regardless of the cause. A throat culture is required to determine if the cause is bacterial. Analgesics such as acetominophen and gargling can relieve the symptoms of throat infection, but to properly treat the bacterial cause of pharyngitis, antibiotics are required.
Streptococcal Pharyngitis
Throat infections caused by Streptococcus pyogenes, or strep throat, account for up to 15 percent of infections. Typically, you cannot distinguish strep throat from other causes of throat infection on clinical grounds alone. However, they are more common in children ages 5 to 15, particularly in the winter and early spring. Fever may be higher with strep throat than with viral causes. Tender, swollen lymph nodes are seen in half of the cases. Characteristic "doughnut lesions," which are red and raised with a yellow center, are unique to strep throat but are seen only in roughly 10 percent of cases. Diagnosis of strep throat can be done by throat culture or rapid antigen testing of a throat swab. Untreated strep throat can result in more serious medical issues such as rheumatic fever and kidney problems. Streptococcal pharyngitis is treatable with penicillin or alternative antibiotics for those allergic to penicillin.
Viral Pharyngitis
Throat infections caused by viruses are by far the most common cause of pharyngitis in children and adults. The virus most commonly implicated in viral throat infections is the Epstein-Barr virus, presenting as enlarged tonsils, enlarged lymph nodes and white patches on the throat. This virus also is known to cause infectious mononucleosis. Viruses that are involved in the common cold, such as rhinoviruses and coronaviruses, also are common causes of throat infection. Adenoviruses can cause an acute pharyngitis and sometimes are seen together in cases of pink eye or conjunctivitis. If Streptococcal pharyngitis and other bacterial causes are ruled out by culture, viral pharyngitis is the likely cause. These infections cannot be treated with antibiotics.
Gonococcal Pharyngitis
Sexually transmitted infections can cause pharyngitis after oral-genital contact. With gonorrhea of the throat, the person may be asymptomatic or may show a thick, exudative or pus pharyngitis. If the clinician suspects gonococcal pharyngitis, the laboratory doing the culture must be informed so the appropriate bacteriological media is used to grow it. This type of pharyngitis is treatable with antibiotics.
Other Causes
Arcanobacterium haemolyticum is a bacterial cause of pharyngitis that closely resembles strep throat; however, it is more common in adolescents and young adults. This infection is treatable with antibiotics.
Diphtheria is a very rare and very dangerous cause of throat infection. The symptoms of diphtheria are very different from other causes of pharyngitis. It is characterized by a thick, gray membrane that covers the back of the pharynx. This is a vaccine-preventable disease and is extremely rare in the United States.
References
- "Koneman's Color Atlas and Textbook of Diagnostic Microbiology, 6th Ed."; Elmer Koneman, M.D.; 2006
- Todar's Online Textbook of Bacteriology: Streptococcus
- Shands Health Care: Viral pharyngitis
