What's the next step for a patient with a negative strep (streptococcal) culture but a small round area of erythema (redness) on the back of the throat?

Management of Pharyngitis with Negative Strep Culture and Localized Erythema

With a negative strep culture, you should withhold antibiotics and provide symptomatic treatment only, as the negative culture reliably rules out Group A streptococcal pharyngitis and most cases are viral in nature. 1

Understanding the Negative Culture Result

A negative throat culture is the gold standard for excluding Group A streptococcal (GAS) pharyngitis, with 90-95% sensitivity when performed correctly. 1 The presence of a small round area of erythema on the posterior pharynx does not change this interpretation, as:

• Neither throat culture nor rapid tests can differentiate between acute GAS infection and asymptomatic streptococcal carriers with concurrent viral pharyngitis. 1
• Pharyngeal erythema is a nonspecific finding that occurs with both viral and bacterial infections. 1
• The negative culture allows you to confidently withhold antibiotics from this patient. 1

Recommended Management Approach

Immediate Actions

• Discontinue or withhold antimicrobial therapy based on the negative culture result. 2 This is a key quality indicator for appropriate pharyngitis management. 2
• Provide symptomatic relief with ibuprofen or acetaminophen (paracetamol) for throat pain and fever. 2
• Reassure the patient that the illness is likely viral and self-limiting. 1

What NOT to Do

Critical pitfall: Do not treat based on clinical symptoms alone when laboratory testing is negative. 2, 3 Nationally, up to 70% of patients with sore throats receive antibiotics, yet only 20-30% actually have GAS pharyngitis. 1 Treating this patient with antibiotics would contribute to:

• Unnecessary antibiotic exposure and adverse effects 2
• Increased antimicrobial resistance 1
• No clinical benefit, as the infection is not streptococcal 2

When to Reconsider or Follow Up

Re-evaluate the patient if:

• Symptoms worsen or persist beyond 5-7 days 4
• New symptoms develop suggesting complications (difficulty swallowing, drooling, respiratory distress) 1
• The patient develops signs of peritonsillar abscess or other suppurative complications 1

Special Considerations for Age Groups

For children and adolescents: If the negative result was from a rapid antigen detection test (RADT) rather than culture, the culture you obtained was the appropriate confirmatory test, as RADTs have only 70-90% sensitivity in this age group. 1, 2

For adults: A negative RADT alone would have been sufficient without culture confirmation, given the low incidence of streptococcal infection and extremely low risk of rheumatic fever in adults. 1, 2

Alternative Diagnoses to Consider

While the negative culture rules out GAS pharyngitis, the localized erythema could represent:

• Viral pharyngitis (most common cause) - including adenovirus, rhinovirus, coronavirus, Epstein-Barr virus 1, 5
• Other bacterial causes (rare) - Groups C and G streptococci, though these do not require antibiotic treatment as they don't cause rheumatic fever 1
• Mycoplasma pneumoniae or Chlamydia pneumoniae (uncommon causes of pharyngitis) 1, 5

However, none of these alternative diagnoses change your management, which remains supportive care only. 2