What is the recommended treatment for invasive streptococci?

Treatment of Invasive Streptococcal Infections

For invasive streptococcal infections, penicillin G 12-24 million units/day IV (or ceftriaxone 2g daily) is the primary treatment, with clindamycin 600-900 mg IV every 8 hours added for Group A streptococcal necrotizing fasciitis or toxic shock syndrome. The specific regimen depends on the clinical syndrome, streptococcal species, and site of infection.

Clinical Syndrome-Based Approach

Necrotizing Fasciitis and Toxic Shock Syndrome (Group A Streptococcus)

• Penicillin G 2-4 million units IV every 4-6 hours PLUS clindamycin 600-900 mg IV every 8 hours is mandatory 1
• Clindamycin suppresses toxin production and is superior to penicillin alone in animal models and observational studies 1
• Urgent surgical debridement is essential and takes priority over antibiotics 1
• Continue antibiotics until no further debridement is needed, patient improves clinically, and fever absent for 48-72 hours 1

Infective Endocarditis

For penicillin-susceptible streptococci (MIC ≤0.125 mg/L):

• Standard 4-week regimen: Penicillin G 12-18 million units/day IV in 4-6 divided doses OR ceftriaxone 2g IV/IM once daily 1
• Short 2-week regimen (uncomplicated native valve endocarditis only): Penicillin G or ceftriaxone PLUS gentamicin 3 mg/kg/day IV in 1 dose 1
• The 2-week regimen achieves >98% cure rate with only 0.7% relapse in studies of 142 patients 2, 3
• Gentamicin/netilmicin can be given once daily in patients with normal renal function 1

For Group A, B, C, or G streptococcal endocarditis:

• Use 4-6 week regimen (NOT 2-week) with penicillin G 12-18 million units/day IV 1
• Add gentamicin for the first 2 weeks for Group B, C, and G streptococci 1
• Group B streptococci have very high mortality in prosthetic valve endocarditis; cardiac surgery is recommended 1
• These organisms produce abscesses and may require adjunctive surgery 1

For penicillin-resistant streptococci (MIC 0.25-2 mg/L):

• Higher doses of penicillin or third-generation cephalosporin required 1
• Consult infectious diseases specialist 1

Skin and Soft Tissue Infections (Non-Necrotizing)

For purulent cellulitis with suspected Group A streptococcus:

• Empiric coverage should include both streptococci and MRSA 1
• Options: clindamycin 600 mg IV/PO every 8 hours alone OR TMP-SMX/tetracycline plus amoxicillin 1
• 5-10 days of therapy 1

For nonpurulent cellulitis:

• Empiric therapy targeting β-hemolytic streptococci: cefazolin 1g IV every 8 hours OR nafcillin/oxacillin 2g IV every 6 hours 1
• Add MRSA coverage only if no response to β-lactam therapy 1

Pyomyositis

• Vancomycin 15 mg/kg IV every 12 hours for initial empirical therapy 1
• Switch to cefazolin or nafcillin/oxacillin if MSSA confirmed 1
• Early surgical drainage is mandatory 1
• 2-3 weeks total therapy; IV initially, then oral once clinically improved and bacteremia cleared 1

Species-Specific Considerations

Streptococcus pneumoniae

• 4 weeks of penicillin, cefazolin, or ceftriaxone for endocarditis; 6 weeks for prosthetic valve 1
• For penicillin-resistant strains (MIC 0.1-4 μg/mL): high-dose penicillin or third-generation cephalosporin 1
• If meningitis present with resistance: high-dose cefotaxime; if MIC ≥2 μg/mL to cefotaxime, add vancomycin and rifampin 1

Streptococcus pyogenes (Group A)

• Penicillin G 2-4 million units IV every 4-6 hours for 4-6 weeks 1
• Ceftriaxone is reasonable alternative 1
• Always add clindamycin for necrotizing infections or toxic shock 1

Group B, C, G Streptococci

• Slightly more resistant to penicillin than Group A 1
• Add gentamicin to penicillin or ceftriaxone for first 2 weeks of 4-6 week course for endocarditis 1
• Early cardiac surgical intervention improves survival 1

Critical Pitfalls to Avoid

• Never use 2-week endocarditis regimen for: prosthetic valves, Group B/C/G streptococci, complicated infections, or symptoms >3 months 1, 2, 4
• Never omit clindamycin for Group A streptococcal necrotizing fasciitis - it suppresses toxin production and is superior to penicillin alone 1
• Never delay surgical intervention for necrotizing infections while waiting for antibiotic effect 1
• Clindamycin resistance in Group A streptococci is <5% in the US but higher in Europe (8-18%); verify susceptibility 1
• For enterococcal endocarditis (not covered here), gentamicin >3 mg/kg/day causes significantly more nephrotoxicity without improved outcomes 2

Penicillin-Allergic Patients

• Vancomycin 30 mg/kg/day IV in 2 divided doses for endocarditis 1
• Vancomycin only for patients unable to tolerate β-lactams 1
• Teicoplanin proposed as alternative but limited data (requires loading: 6 mg/kg every 12h for 3 doses, then 6-10 mg/kg/day) 1

Duration of Therapy

• Group A streptococcal infections: minimum 10 days to reduce rheumatic fever risk 5
• Endocarditis: 4 weeks standard, 2 weeks for uncomplicated penicillin-susceptible cases, 6 weeks for prosthetic valves 1
• Necrotizing fasciitis: until no further debridement needed and afebrile 48-72 hours 1
• Pyomyositis: 2-3 weeks total 1