Streptococcal Pharyngitis

Etiology

Streptococcus pyogenes, also known as Group A Streptococcus (GAS), is a facultative gram-positive coccus that grows in chains.

Epidemiology

GAS is the most common bacterial cause of pharyngitis in children and adolescents, with a peak incidence in winter and early spring.[2] GAS pharyngitis is also more common in school-aged children or in those with a direct relation to school-aged children. A recent meta-analysis showed that the prevalence of GAS pharyngitis in those less than 18 years old who present to an outpatient center for treatment for a sore throat was 37%, and for children younger than 5, it was 24%.[6] However, in adults, GAS pharyngitis will typically occur before the age of 40 and decline steadily after that.[7]

History and Physical

Multiple studies have shown that history and physical examination alone fail to aid the physician in accurately diagnosing GAS pharyngitis in patients.[8] However, a history that consists of a sore throat, abrupt onset of fever, the absence of a cough, and exposure to someone with GAS pharyngitis within the previous 2 weeks may be suggestive of GAS pharyngitis.[9][10] Physical exam findings including cervical lymphadenopathy, pharyngeal inflammation, and tonsillar exudate. Palatine petechiae and uvular edema are also suggestive.[9][10]

Evaluation

The modified Centor criteria is a clinical aid for physicians to determine who to test and treat when GAS pharyngitis is suspected. However, the Infectious Disease Society of American (IDSA) currently notes that the signs and symptoms of GAS pharyngitis overlap too broadly with other infectious and non-infectious causes to allow for a precise diagnosis to be made based upon history and physical alone.

The broad overlap of signs and symptoms seen in bacterial and viral pharyngitis coupled with the inaccuracy of medical providers when distinguishing GAS pharyngitis from other causes, the IDSA recommends confirmatory bacterial testing in all cases except when a clear viral etiology is expected. Diagnostic testing in children younger than 3 is not recommended because both GAS pharyngitis and acute rheumatic fever are rare in this age group. However, children under 3 years of age with risk factors, including but not limited to siblings with GAS pharyngitis, may be considered for testing.[5]

For those who undergo testing, the IDSA recommends that a rapid antigen detection test (RADT) be employed as the first-line measure to aid the physician in the diagnosis of GAS pharyngitis. Positive tests do not need to be backed up by a throat culture in all age groups due to the highly specific nature of the RADT. In children, a negative RADT should be followed by a throat culture, but this is not needed in adults due to both the low incidence of GAS pharyngitis and acute rheumatic fever seen in this population. Anti-streptococcal antibody titers are not recommended to aid the physician in the acute diagnosis of GAS pharyngitis because the test reflects previous infections. Following treatment, a test of cure is not needed but may be considered in special circumstances.[5]

Treatment / Management

The main goals of treatment for GAS pharyngitis include reducing a patient’s duration and severity of symptoms, preventing acute and delayed complications, and preventing the spread of infection to others.

Those with GAS pharyngitis should be treated with either penicillin or amoxicillin, given their relatively low cost and low adverse effect profile. Penicillin can be prescribed as either 250 mg twice or three times daily for children and 250 mg 4 times daily for adults. If the clinician or patient prefers an intramuscular approach for penicillin treatment, then benzathine penicillin G can be given as a one-time dose of 600,000 units if the patient is less than 27 kg and 1.2 million U if the patient is greater than or equal to 27 kg. If amoxicillin is chosen by the prescriber, then the medication can be given 50 mg/kg, once daily with a maximum of 1000 mg per dose or 25 mg/kg twice a day with a maximum of 500 mg per dose. With either the penicillin or oral amoxicillin route, a total of 10 days of treatment should be completed.[5](A1)

For those with an allergy to penicillin, clindamycin (7 mg/kg/dose, 3 times daily; max = 300 mg/dose; 10 day duration), clarithromycin (7.5 mg/kg/dose. twice daily; max = 250mg/dose; 10 day duration) or azithromycin (12 mg/kg, once daily; max = 500mg/dose; 5 day duration) can be prescribed. A first-generation cephalosporin (cephalexin 20 mg/kg/dose, twice daily, max = 500mg/dose; duration 10 days) can also be used for those patients without an anaphylactoid reaction to penicillin.[5](A1)

As adjunctive therapy for the patient with GAS pharyngitis, the IDSA recommends acetaminophen or an NSAID to control pain associated with the disease or any fever that should develop. Currently, the ISDA does not recommend routine adjunctive therapy with corticosteroids for those with GAS pharyngitis.[5](A1)

Following antibiotic treatment, patients may see the resolution of symptoms within one to 3 days and may return to work or school after 24 hours of treatment. A test of cure is not recommended after a course of treatment unless a patient has a history of acute rheumatic fever or another GAS complication. Likewise, post-exposure prophylaxis is not recommended unless a patient has a history of acute rheumatic fever, during outbreaks of non-supportive complications, or when GAS infections are seen recurrently in households or close contacts. Prevention of the disease is through proper hand hygiene, and it also is key to halting disease progression within close quarters.[5](A1)

Differential Diagnosis

Infectious Causes[5]

• Respiratory viruses (parainfluenza, rhinovirus, coxsackievirus, adenovirus, etc.)
• Arcanobaceterium haemolyticum
• Mycoplasma species
• Chlamydia species
• Corynebacterium diphtheria
• Acute HIV infection
• Neisseria gonorrhoeae
• Treponema pallidum
• Epstein-Barr virus
• Fusobacterium necrophorum

Non-infectious Causes[5]

• Allergies
• Gastroesophageal reflux disease
• Exposure to second-hand smoke
• Trauma
• Autoimmune disorders (Behçet syndrome, Kawasaki, etc.)
• Foreign body

Complications

Suppurative complications seen with GAS pharyngitis include tonsillopharyngeal cellulitis or abscess, otitis media, sinusitis, necrotizing fasciitis, bacteremia, meningitis, brain abscess, and jugular vein septic thrombophlebitis. Non-suppurative complications of GAS pharyngitis include acute rheumatic fever, post-streptococcal reactive arthritis, scarlet fever, streptococcal toxic shock syndrome, acute glomerulonephritis, and pediatric autoimmune neuropsychiatric disorder associated with group A streptococci (PANDAS).