What is the antibiotic of choice for a patient positive for both streptococcal (strep) infection and infectious mononucleosis (mono)?

Antibiotic Choice for Patients with Both Strep Throat and Infectious Mononucleosis

For patients with concurrent streptococcal infection and infectious mononucleosis, amoxicillin should be avoided and clindamycin is the antibiotic of choice. 1

Rationale for Avoiding Amoxicillin/Penicillins

While penicillin and amoxicillin are typically first-line treatments for streptococcal pharyngitis, these medications must be avoided in patients with infectious mononucleosis due to the high risk (>90%) of developing a severe maculopapular rash. This is a well-documented drug reaction specific to the combination of EBV infection and aminopenicillins.

Recommended Treatment Approach

First-line Treatment:

• Clindamycin: 7 mg/kg three times daily (maximum 300 mg per dose) for 10 days 1
  • Clindamycin is particularly effective against Group A Streptococcus
  • Has the added benefit of suppressing streptococcal toxin and cytokine production 2

Alternative Options (for penicillin-allergic patients with strep who also have mono):

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1

  • Note: While effective, azithromycin has more gastrointestinal side effects than penicillins 3
  • FDA approved for pharyngitis/tonsillitis caused by Streptococcus pyogenes as an alternative to first-line therapy 4

• Clarithromycin: 7.5 mg/kg twice daily (maximum 250 mg per dose) for 10 days 1

  • Consider local resistance patterns before prescribing macrolides

Important Clinical Considerations

Diagnosis Confirmation

• Confirm both diagnoses before treatment:
  • Strep: Rapid antigen detection test (RADT) and/or throat culture
  • Mono: Monospot test or EBV-specific antibody testing
  • Use Centor Criteria to assess likelihood of streptococcal infection 1

Treatment Duration

• Complete the full prescribed course of antibiotics:
  • 10 days for clindamycin and clarithromycin
  • 5 days for azithromycin 1
  • Completing the full course is essential to prevent acute rheumatic fever and ensure complete eradication of Group A Streptococcus

Monitoring and Follow-up

• Monitor for:
  • Resolution of symptoms
  • Development of suppurative complications
  • Potential adverse effects of antibiotics

Symptomatic Relief

• Provide symptomatic treatment alongside antibiotics:
  • NSAIDs or acetaminophen for pain and fever
  • Adequate hydration
  • Rest
  • Warm salt water gargles

Potential Pitfalls and Caveats

1. Misdiagnosis: Symptoms of strep and mono can overlap, making diagnosis challenging. Ensure proper testing for both conditions.

2. Antibiotic Resistance: Be aware of local resistance patterns, particularly for macrolides. In areas with high macrolide resistance, clindamycin may be the only viable option 1.

3. Treatment Failure: If symptoms persist despite appropriate antibiotic therapy, consider:

   • Antibiotic resistance
   • Poor compliance
   • Development of complications
   • Incorrect initial diagnosis

4. Complications of Mono: Monitor for potential complications of infectious mononucleosis, including:

   • Splenic rupture (avoid contact sports for at least 3-4 weeks)
   • Airway obstruction from tonsillar hypertrophy
   • Hepatitis

5. Household Contacts: It is generally not necessary to perform throat cultures or provide treatment for household contacts of patients with Group A streptococcal pharyngitis, except in specific high-risk situations 2.

By following these guidelines, clinicians can effectively manage the challenging clinical scenario of concurrent streptococcal infection and infectious mononucleosis while avoiding the severe rash associated with aminopenicillin use in mono patients.