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Acute inflammation of the structures of the pharynx and tonsils, also known as tonsillopharyngitis, represents a common condition that is usually encountered in outpatients seeking healthcare interventions. Sore throat and fever are the dominant symptoms of this condition which usually follows a benign course that resolves without any antimicrobial treatment.
Although most episodes of pharyngitis (or tonsillopharyngitis, which are interchangeable terms) are caused by viruses, beta-hemolytic group A streptococcus (Streptococcus pyogenes) is responsible for 5 to 20% of cases in adults and up to 30% of cases in children. This condition is also known as streptococcal pharyngitis or “strep throat”.
Streptococcus pyogenes is an extracellular gram-positive pathogen of major clinical importance as it can trigger postinfectious syndromes such as acute rheumatic fever and poststreptococcal glomerulonephritis approximately one to three weeks after the infection of the pharynx. Therefore etiologic diagnosis should be pursued in order to initiate timely antibiotic therapy.
Beta-hemolytic group A streptococcus is easily transmitted by inhalation of organisms in large droplets or by direct contact with respiratory secretions. Strep throat is especially contagious early in the course of the disease and for the first two weeks after the organism had been acquired (unless antibiotic treatment is implemented). The incubation period ranges from 24 to 72 hours.
Children from 5 to 15 years of age experience streptococcal pharyngitis more frequently in comparison to other age groups. However, the disease is quite unusual in infancy (although it can occur). There is a serological confirmation of beta-hemolytic group A streptococcus in approximately one in four school-aged children with acute sore throat. Cases of strep throat usually peak in the late winter and early spring months.
The most data on strep throat in young adults stem from research in semi-closed populations. Military training camps represent an ideal milieu for streptococcal infections, as a number of young men and women from diverse socioeconomic and ethnic backgrounds are housed in close quarters and subjected to extraordinary physical stress.
Still, the proportion of adult streptococcal pharyngitis is considerably lower than that in children, and in several studies the figure is as low as 5 to 10%. Furthermore, the risk of development of acute rheumatic fever in adults is significantly lower than in children, even if Streptococcus pyogenes goes undiagnosed and untreated.
Abrupt onset of fever and sore throat are hallmarks of streptococcal pharyngitis. On the other hand, cough, hoarseness, stridor, rhinorrhea, conjunctivitis and diarrhea are quite unusual. In older children several nonspecific signs and symptoms can be associated with the disease, including headache, nausea, abdominal pain, malaise and vomiting (especially in older children).
The pharynx is erythematous and petechiae (small red dots) can be seen on the soft palate. Tonsils (if present) are usually enlarged and erythematous with patchy exudates on their surfaces, while the tongue is red and swollen (often designated “strawberry tongue” for that reason). Lymph nodes of the neck can be enlarged and tender.
Because the aforementioned clinical signs and symptoms of pharyngitis caused by beta-hemolytic group A streptococcus can be non-specific, establishing an accurate diagnosis often remains difficult – even for experienced physicians. Therefore it has become standard practice to seek bacteriological confirmation of the diagnosis.
Penicillin V remains the gold standard in the treatment of Streptococcus pyogenes as it is both inexpensive and effective. Antibiotics can also reduce the incidence of acute rheumatic fever, and children with streptococcal pharyngitis can return to school 1-2 days upon the introduction of antibiotic therapy.
Suppurative complications that ensued from the spread of beta-hemolytic group A streptococcus to adjacent structures (such as peritonsillar abscess) were quite common before the advent of antimicrobial therapy and usually appeared within one week after onset of pharyngitis. Otitis media and sinusitis may also occur as potential complications, but antibiotics made them practically disappear.
The nonsuppurative sequelae such as acute rheumatic fever, acute poststreptococcal glomerulonephritis and reactive arthritis are well-recognized complications of strep throat, albeit the underlying pathogenic mechanisms are still poorly understood. Molecular mimicry is thought to play a significant role in these processes.
Streptococcal carriage is very cumbersome to eliminate with conventional penicillin treatment, thus therapy is not warranted in most circumstances. A short course of rifampin (together with penicillin) has been demonstrated as the most effective option in a majority of patients.
One of the future goals is to prevent streptococcal pharyngitis and (even more importantly) poststreptococcal sequelae with a vaccine. At the moment several different vaccine models are in preclinical studies, holding promise for an effective and safe approach in preventing infection with this microorganism.