How do you differentiate and treat streptococcal vs staphylococcal infections?

Differentiating and Treating Streptococcal vs Staphylococcal Infections

The key to differentiating streptococcal from staphylococcal skin infections lies in their clinical presentation, with streptococcal infections typically causing diffuse, non-purulent cellulitis while staphylococcal infections usually present with purulent drainage or abscesses that require drainage. 1

Clinical Differentiation

Streptococcal Infections

• Typically present as diffuse, spreading erythema with minimal purulence 2
• Most commonly affect the lower extremities 2
• Cause conditions like erysipelas, cellulitis without purulence, and impetigo 1
• Often cause more intense systemic symptoms 3
• Beta-hemolytic streptococci (BHS) are responsible for approximately 73% of diffuse, non-culturable cellulitis 3

Staphylococcal Infections

• Usually present as localized abscesses, pustules, or bullae with purulent drainage 1, 2
• More commonly affect the face, with hair follicles and sweat ducts as initial sites 2
• Characterized by a narrow rim of erythema around purulent centers 2
• Intense cellulitis surrounding lesions suggests a virulent, penicillin-resistant strain 2
• Often culturable (unlike many streptococcal infections) 3

Diagnostic Approach

When to Culture

• Obtain cultures from abscesses and purulent SSTIs in patients: 1
  • Receiving antibiotic therapy
  • With severe local infection or systemic illness
  • Who have not responded to initial treatment
  • When there's concern for an outbreak

Specific Tests

• For streptococcal pharyngitis: rapid antigen detection tests (RADT) or throat cultures 1
• For tularemia: serologic tests are preferred 1
• For bubonic plague: Gram stain and culture of aspirated material from suppurative lymph nodes 1

Treatment Approach

For Purulent Infections (Likely Staphylococcal)

• Primary treatment is incision and drainage for abscesses 1
• For outpatient treatment of purulent cellulitis (empiric coverage for CA-MRSA): 1
  • Clindamycin (A-II)
  • Trimethoprim-sulfamethoxazole (TMP-SMX) (A-II)
  • Tetracycline (doxycycline or minocycline) (A-II)
  • Linezolid (A-II)

For Non-Purulent Infections (Likely Streptococcal)

• For outpatient treatment of non-purulent cellulitis: 1, 3
  • Beta-lactam antibiotics (penicillin or amoxicillin) are first-line therapy
  • 5-10 days of therapy is recommended
  • 95.8% response rate to beta-lactam antibiotics for diffuse, non-culturable cellulitis 3

For Combined Coverage

• When coverage for both streptococci and staphylococci is desired: 1
  • Clindamycin alone (A-II)
  • TMP-SMX or tetracycline plus a beta-lactam (amoxicillin) (A-II)
  • Linezolid alone (A-II)

For Hospitalized Patients with Complicated SSTIs

• Empiric therapy should include coverage for MRSA pending culture results: 1
  • IV vancomycin (A-I)
  • Oral or IV linezolid 600 mg twice daily (A-I)
  • Daptomycin 4 mg/kg/dose IV once daily (A-I)
  • Telavancin 10 mg/kg/dose IV once daily (A-I)
  • Clindamycin 600 mg IV or PO 3 times a day (A-III)

Special Considerations

Pediatric Patients

• Tetracyclines should not be used in children <8 years of age 1
• For impetigo in children, mupirocin 2% topical ointment can be used 1
• In hospitalized children with complicated SSTIs, vancomycin is recommended 1

Duration of Treatment

• For most bacterial SSTIs: 7-14 days of therapy is recommended 1
• Recent evidence suggests that shorter courses (5-7 days) may be effective for streptococcal pharyngitis 4

Common Pitfalls and Caveats

• Avoid using penicillin alone for suspected staphylococcal infections due to high rates of penicillin resistance 2, 5
• Do not rely on clinical features alone to distinguish between streptococcal and staphylococcal infections in older children and adults, as this can lead to treatment failures 5
• For recurrent streptococcal pharyngitis, avoid continuous long-term antimicrobial prophylaxis 1
• The oral route should not be relied upon in patients with severe illness, nausea, vomiting, or intestinal hypermotility 6
• Rifampin should not be used as a single agent or as adjunctive therapy for SSTIs 1

By carefully assessing the clinical presentation and following these treatment guidelines, clinicians can effectively differentiate and treat streptococcal and staphylococcal infections, improving patient outcomes and reducing unnecessary antibiotic use.