What is the treatment for resistant strep (streptococcal) infections?

Treatment of Resistant Streptococcal Infections

For resistant streptococcal infections, the combination of clindamycin and penicillin is the most effective treatment, particularly for severe infections like necrotizing fasciitis caused by Group A streptococci. 1

Treatment Options Based on Infection Type

Group A Streptococcal Pharyngitis with Resistance

• For penicillin treatment failures or suspected resistant strep pharyngitis, clindamycin (20-30 mg/kg/day in three doses, maximum 300 mg per dose for 10 days) is the most effective option with strong evidence 1
• Alternative regimens for chronic carriers or resistant cases include:
  • Penicillin with rifampin combination (penicillin for 10 days with rifampin added for the last 4 days) 1
  • Amoxicillin-clavulanate (40 mg amoxicillin/kg/day in three doses) for 10 days 1
  • Penicillin G benzathine (intramuscular) with oral rifampin 1

Macrolide Options for Penicillin-Allergic Patients

• For patients with penicillin allergy who cannot take clindamycin, macrolides may be used, but resistance should be considered:
  • Azithromycin (12 mg/kg once daily, maximum 500 mg) for 5 days 1
  • Clarithromycin (7.5 mg/kg twice daily, maximum 250 mg per dose) for 10 days 1
• Note: Group A streptococcus resistance to macrolides is well-documented and varies geographically 1, 2

Severe Invasive Streptococcal Infections

• For necrotizing fasciitis or streptococcal toxic shock syndrome:
  • Combination of clindamycin (600-900 mg IV every 8 hours) plus penicillin (2-4 MU IV every 4-6 hours) is recommended 1
  • The rationale for adding clindamycin is based on its toxin suppression properties and superior efficacy compared to β-lactams alone 1

For Penicillin-Allergic Patients with Severe Infections

• For patients with severe penicillin hypersensitivity and invasive streptococcal infections, options include:
  • Vancomycin 1
  • Linezolid 1
  • Quinupristin/dalfopristin 1
  • Daptomycin 1

Mechanisms of Resistance and Treatment Considerations

• Penicillin failure in treating streptococcal infections may be due to:

  • Presence of β-lactamase producing bacteria that "protect" streptococci 3
  • Poor penetration of penicillin into tonsillar tissues allowing intracellular streptococci to survive 3
  • Co-aggregation between Group A streptococci and other bacteria 3

• For skin and soft tissue infections with resistant streptococci:

  • Surgical drainage is essential for abscesses 1
  • For complicated skin/soft tissue infections, vancomycin, linezolid, daptomycin, or clindamycin are recommended 1

Special Considerations

• Duration of therapy:

  • For pharyngitis: minimum 10 days to prevent rheumatic fever 4
  • For complicated skin/soft tissue infections: 7-14 days based on clinical response 1

• Monitoring:

  • Cultures should be taken following completion of treatment for streptococcal pharyngitis to confirm eradication 4
  • For necrotizing fasciitis, repeated surgical debridement is often necessary until infection is controlled 1

• Pediatric considerations:

  • Tetracyclines should not be used in children under 8 years of age 1
  • For children with complicated infections, clindamycin (10-13 mg/kg/dose IV every 6-8 hours) or vancomycin is recommended 1

Important Caveats

• Penicillin remains the drug of choice for non-resistant streptococcal infections due to no documented resistance, narrow spectrum, and low cost 1
• Despite in vitro susceptibility to penicillin, clinical failures may occur due to various factors including bacterial interactions and intracellular persistence 3
• Rifampin should not be used as monotherapy due to rapid development of resistance 1
• For bloodstream infections from soft tissue sources, intravenous therapy may be superior to oral therapy for beta-hemolytic streptococcal infections 5

By addressing the specific resistance mechanisms and using appropriate combination therapy, most resistant streptococcal infections can be effectively treated with improved clinical outcomes.