Pharyngitis

Etiology

- Majority of adult cases (80-90%) of pharyngitis are of viral etiology and do not require antimicrobial therapy.

- Group A Streptococcus (GAS) is most common bacterial cause of pharyngitis.

- Occasionally pharyngitis is caused by Group C, G Streptococci and Arcanobacterium haemolyticum. A. haemolyticum causes pharyngitis in young adults (12-30 years old). Many have scarlatiniform rash, most marked on the extremities. Notify laboratory if clinically suspected as culture requires prolonged incubation.

Clinical presentation

- The following suggests a viral etiology: conjunctivitis, cough, hoarseness, rhinorrhea, and/or diarrhea. Patients with these symptoms should not have a throat swab taken for culture or rapid antigen-detection test (RADT).

- Typical signs/symptoms of GAS pharyngitis:

1. pharyngeal or tonsillar exudate

2. fever

3. tenderness/enlargement of anterior cervical lymph nodes

4. absence of cough

Increased risk if exposure to individual with strep throat in previous 2 weeks.

- Infectious for 2-5 days prior to symptoms.

- GAS pharyngitis is most common in children between 5-10 years old, and in fall and winter.

- Consider Lemierre's syndrome (jugular vein suppurative phlebitis) in teenagers/young adults with pharyngitis, persistent fever, and neck pain. Recommend aerobic and anaerobic blood cultures and imaging of neck veins with ultrasound or CT.

Diagnosis

- Cannot diagnose GAS pharyngitis with symptoms alone (even if all 4 signs/symptoms listed above are present).  Throat swab for culture or rapid antigen-detection test recommended.

- Newer RADT have high specificity and much improved sensitivity therefore confirmatory throat culture is no longer recommended for negative RADT results.

Antibiotic therapy

- Awaiting throat culture results before initiating antibiotic therapy remains a reasonable strategy as:

• Group A Strep pharyngitis is a self-limited disease (8-10 days)

• antibiotic therapy can be delayed for up to 9 days after onset of illness and still prevent acute rheumatic fever

• delay in antibiotic therapy may decrease reinfection rates

• unnecessary antibiotic use can be avoided in ~50% of patients.

- Antibiotic therapy decreases: severity of symptoms, duration of symptoms by ~1 day, risk of transmission (after 24h of therapy), and likelihood of suppurative complications and of rheumatic fever.

- Group A Streptococci:

• no in vitro resistance to penicillin

• significant macrolide and clindamycin resistance

- Quinolones and broad-spectrum cephalosporins NOT indicated in pharyngitis.

• too broad-spectrum, potential to increase resistance

- Follow up cultures are not routinely recommended unless:

• history of rheumatic fever (increased risk for recurrence)

• persistent symptoms

• recurrent symptoms.