Treatment of Gram-Positive Cocci in Chains (Streptococcal Infections)
Penicillin remains the treatment of choice for streptococcal infections due to its proven efficacy, safety, narrow spectrum, and low cost. 1
Initial Antibiotic Selection
For Pharyngitis (Group A Streptococcus)
Penicillin V 500 mg orally four times daily for 10 days is the first-line treatment for non-allergic patients. 1 Alternatively, amoxicillin 500 mg three times daily for 10 days is equally effective and more palatable. 1, 2
- For patients unlikely to complete oral therapy: Intramuscular benzathine penicillin G is preferred as a single dose. 1
- For penicillin-allergic patients: Erythromycin is suitable, or first/second-generation cephalosporins if no immediate hypersensitivity to β-lactams exists. 1
- Treatment duration must be 10 days minimum to prevent acute rheumatic fever, regardless of symptom resolution. 1, 2, 3
For Skin and Soft Tissue Infections
For nonpurulent cellulitis (no drainage/exudate), empirical therapy targeting β-hemolytic streptococci is recommended. 1
- Outpatient options: Cefazolin or other β-lactams for 5-10 days. 1
- If MRSA coverage also needed: Clindamycin 300-600 mg orally three times daily covers both streptococci and MRSA. 1
- Hospitalized patients with complicated infections: IV vancomycin, linezolid, or daptomycin for 7-14 days. 1
For Necrotizing Fasciitis (Group A Streptococcus)
Combination therapy with penicillin 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 based on animal studies and observational data. 1
- Penicillin is added because only 0.5% of macrolide-resistant Group A streptococci are clindamycin-resistant in the US. 1
- Surgical debridement is essential and patients should return to the operating room every 24-36 hours until no further debridement is needed. 1
For Bacteremia/Endocarditis (Viridans Streptococci, S. mitis/oralis)
For penicillin-susceptible strains (MIC ≤0.125 mg/L): Penicillin G 12-18 million units/day IV in divided doses for 4 weeks, or ceftriaxone 2g IV once daily for 4 weeks. 1, 4
- For uncomplicated bacteremia without endocarditis: 2 weeks of therapy is sufficient. 1, 4
- For native valve endocarditis: 4 weeks minimum. 1, 4
- For prosthetic valve endocarditis: 6 weeks minimum. 1, 4
- For penicillin-resistant strains (MIC >0.125 mg/L): Add gentamicin 3 mg/kg/day IV once daily for at least 2 weeks to penicillin or ceftriaxone. 1, 4
Critical Monitoring Requirements
- Obtain repeat blood cultures 2-4 days after starting therapy to document clearance in bacteremia cases. 4
- Perform echocardiography on all patients with streptococcal bacteremia to exclude endocarditis, with transesophageal preferred. 4
- Continue therapy for 48-72 hours after fever resolution and symptom improvement. 1, 2
Common Pitfalls to Avoid
Do not stop antibiotics early even if symptoms resolve: This increases treatment failure rates and risk of rheumatic fever. 1, 2, 3
Do not assume penicillin susceptibility without testing: Resistance rates for viridans streptococci exceed 30% in many regions. 4
Do not use rifampin for streptococcal infections: It is reserved for staphylococcal prosthetic valve endocarditis only. 1, 4
Do not rely on oral therapy in severely ill patients: Use IV antibiotics for patients with nausea, vomiting, or severe illness. 3
Do not routinely culture or treat asymptomatic household contacts unless special circumstances exist (outbreak settings, repeated infections). 1
Special Populations
Pediatric Dosing
- Penicillin V: 200,000 units/kg/day divided into 4-6 doses for 10 days. 1
- Amoxicillin: 25-45 mg/kg/day divided every 8-12 hours depending on severity. 2
- Infants <3 months: Maximum 30 mg/kg/day amoxicillin divided every 12 hours due to immature renal function. 2