How do you differentiate and treat bacterial vs viral pharyngitis?

Differentiating and Treating Bacterial vs Viral Pharyngitis

Microbiological testing is essential for differentiating bacterial from viral pharyngitis, as clinical features alone are insufficient for accurate diagnosis. 1, 2

Clinical Differentiation

Bacterial Pharyngitis Features

• Group A Streptococcus (GAS) is the most common bacterial cause of pharyngitis requiring antibiotic treatment 1, 2
• More common in children 5-15 years of age, particularly in winter and early spring 1
• Characteristic features include:
  • Sudden onset of sore throat 1
  • Fever 1
  • Tonsillopharyngeal inflammation and exudates 1
  • Tender anterior cervical lymphadenopathy 1
  • Absence of cough 1
  • Palatal petechiae 1
  • Scarlatiniform rash 1

Viral Pharyngitis Features

• Viral causes account for the majority of acute pharyngitis cases 2
• Associated features suggesting viral etiology:
  • Cough 1
  • Rhinorrhea/nasal congestion 1
  • Conjunctivitis 1
  • Hoarseness 1
  • Discrete ulcerative stomatitis 1
  • Diarrhea 1
  • Viral exanthem 1

Diagnostic Approach

When to Test

• Testing is not recommended if clinical features strongly suggest viral etiology (cough, rhinorrhea, hoarseness, oral ulcers) 1
• Testing should be performed when bacterial pharyngitis is suspected based on clinical presentation 1, 2
• The Modified Centor criteria can help identify patients with low probability of GAS pharyngitis who don't warrant testing (fewer than 3 criteria: fever, tonsillar exudates, tender anterior cervical adenopathy, absence of cough) 1

Recommended Testing Methods

• Rapid antigen detection test (RADT) is recommended as the initial test 1, 2
• A positive RADT is diagnostic for GAS pharyngitis 1
• In children and adolescents with negative RADT, a backup throat culture should be performed 1
• Backup culture is generally not necessary in adults with negative RADT due to lower incidence of GAS and lower risk of rheumatic fever 1

Treatment Recommendations

Bacterial Pharyngitis Treatment

• Penicillin remains the treatment of choice for GAS pharyngitis due to its proven efficacy, safety, narrow spectrum, and low cost 1
• Treatment options include:
  • Oral penicillin V for 10 days 1, 3
  • Intramuscular benzathine penicillin G for patients unlikely to complete oral therapy 1
  • Erythromycin for penicillin-allergic patients 1
  • First-generation cephalosporins for patients without immediate hypersensitivity to β-lactams 1
• Azithromycin (12 mg/kg once daily for 5 days) is an alternative that has shown clinical and microbiological superiority to penicillin in some studies 4

Viral Pharyngitis Treatment

• Antibiotic treatment is not justified for viral pharyngitis 1
• Symptomatic treatment is recommended:
  • Antipyretics 1
  • Cough suppressants (dextromethorphan or codeine) 1
  • Expectorants (guaifenesin) 1
  • First-generation antihistamines (diphenhydramine) 1
  • Decongestants (phenylephrine) 1

Common Pitfalls to Avoid

• Relying solely on clinical impression without microbiological confirmation leads to overuse of antibiotics 2
• Treating viral pharyngitis with antibiotics provides no benefit and increases risk of adverse effects 1
• Failing to recognize that a patient may be a GAS carrier with concurrent viral pharyngitis 2
• Not considering other bacterial causes of pharyngitis beyond GAS (such as groups C and G streptococci, C. diphtheriae, N. gonorrhoeae) 1, 2
• Overlooking potentially serious throat infections such as peritonsillar abscess, epiglottitis, or Lemierre syndrome in patients with severe symptoms 1, 5

Special Considerations

• For recurrent episodes of GAS pharyngitis, consider:
  • Retreatment with the same antimicrobial agent 1
  • Intramuscular benzathine penicillin G if compliance with oral therapy is questionable 1
  • Clindamycin or amoxicillin/clavulanate for multiple recurrences, as they have shown high rates of pharyngeal eradication 1
• The primary goals of treatment for GAS pharyngitis are:
  • Prevention of acute rheumatic fever 1
  • Prevention of suppurative complications 1
  • Abatement of clinical symptoms 1
  • Reduction of infectivity 1