What is the treatment for an infection caused by gram-positive cocci in chains?

Treatment of Gram-Positive Cocci in Chains

For infections caused by gram-positive cocci in chains (streptococci), penicillin remains the first-line treatment, with clindamycin added for severe invasive infections like necrotizing fasciitis to suppress toxin production. 1, 2

Identifying the Pathogen

Gram-positive cocci in chains are streptococci, which include several clinically important species:

• Group A Streptococcus (S. pyogenes): Most common cause of pharyngitis and skin/soft tissue infections 3
• Viridans group streptococci: Associated with endocarditis and polymicrobial infections 2
• Groups B, C, and G streptococci: Cause skin infections, bacteremia, and occasionally necrotizing fasciitis 1, 4
• Enterococcus species: Technically streptococci, found in intra-abdominal and urinary infections (7.7-16.5% of intra-abdominal cases) 2

Treatment by Clinical Scenario

Mild to Moderate Community-Acquired Infections

For uncomplicated streptococcal pharyngitis or cellulitis, use penicillin or amoxicillin for a minimum of 10 days to prevent acute rheumatic fever. 3, 5

• Penicillin V: 200,000-300,000 U/kg/day IV divided every 4 hours (up to 12-24 million units daily) 6
• Amoxicillin: 500 mg every 12 hours or 250 mg every 8 hours for adults; 25 mg/kg/day divided every 12 hours for children 3
• Treatment must continue for at least 10 days for S. pyogenes infections to prevent rheumatic fever 3, 5
• Continue therapy 48-72 hours beyond symptom resolution 3

Severe Invasive Streptococcal Infections

For necrotizing fasciitis or streptococcal toxic shock syndrome caused by Group A streptococci, use the combination of penicillin PLUS clindamycin. 1, 2

• Penicillin: 2-4 million units every 4-6 hours IV 1
• Clindamycin: 600-900 mg every 8 hours IV 1, 2
• Rationale: Clindamycin suppresses toxin production, modulates cytokine (TNF) response, and demonstrates superior efficacy versus penicillin alone in animal studies and observational data 1, 2
• Critical caveat: Only 0.5% of macrolide-resistant Group A streptococci in the US are clindamycin-resistant, but resistance is increasing 1

Polymicrobial Infections with Streptococci

For mixed infections involving streptococci (such as intra-abdominal infections or polymicrobial necrotizing fasciitis), use ampicillin-sulbactam plus clindamycin plus ciprofloxacin. 1

• Ampicillin-sulbactam: 1.5-3.0 g every 6-8 hours IV 1
• Clindamycin: 600-900 mg every 8 hours IV 1
• Ciprofloxacin: 400 mg every 12 hours IV 1
• Alternative regimens: Piperacillin-tazobactam 3.37 g every 6-8 hours IV, or carbapenems (imipenem 1 g every 6-8 hours, meropenem 1 g every 8 hours, ertapenem 1 g daily) 1, 2
• Ampicillin provides coverage for susceptible enteric organisms, group B/C/G streptococci, Peptostreptococcus, and some anaerobes 1

Penicillin-Allergic Patients

For patients with severe penicillin hypersensitivity, use vancomycin, linezolid, quinupristin/dalfopristin, or daptomycin. 1, 6

• Vancomycin: 15-20 mg/kg every 8-12 hours IV with target trough 15-20 μg/mL for severe infections 2, 6
• Monitor trough levels in patients with renal impairment 6
• Alternative agents include linezolid (preferred for vancomycin-resistant enterococci), daptomycin, or ceftaroline 2

High-Risk Scenarios Requiring Vancomycin

Add vancomycin empirically when gram-positive cocci are identified in blood cultures before final identification, or in patients with:

• Clinically suspected serious catheter-related infections 1, 2
• Known colonization with penicillin/cephalosporin-resistant pneumococci or MRSA 1, 2
• Hypotension or cardiovascular impairment 1, 2
• Neutropenia with fever 1, 2

Discontinue vancomycin after 24-48 hours if cultures remain negative or susceptibilities show penicillin sensitivity. 1, 2

Enterococcal Infections

For ampicillin-susceptible enterococci causing serious infections (endocarditis, bacteremia), use ampicillin plus gentamicin. 6

• Ampicillin: 200-300 mg/kg/day IV divided every 4-6 hours (up to 12 g daily) 6
• Gentamicin: Added for synergy in serious infections 6
• Enterococci are associated with worse outcomes in secondary peritonitis and require specific coverage 2

Duration of Therapy

Treat for 7-14 days for most streptococcal skin and soft tissue infections, but extend therapy if infection has not improved. 2

• Continue antibiotics until repeated operative procedures are no longer needed (for necrotizing infections) 1, 2
• Ensure clinical improvement is obvious and fever has been absent for 48-72 hours 1, 2
• For S. pyogenes infections, minimum 10 days to prevent rheumatic fever 3, 5
• Obtain cultures following treatment completion to confirm eradication 5

Critical Pitfalls to Avoid

• Never rely on oral antibiotics for severe illness, nausea/vomiting, or intestinal hypermotility - absorption is unreliable 5
• Do not use ceftazidime alone - it lacks adequate gram-positive coverage 1
• Avoid empiric vancomycin overuse - it has no survival benefit for all gram-positive bacteremia and promotes resistance 1, 2
• Do not delay surgical intervention for necrotizing fasciitis - patients require debridement every 24-36 hours until no further necrosis is found 1
• Beware of viridans streptococci in neutropenic patients - they can cause serious infections with mortality higher in those not initially treated with vancomycin 1

Surgical Considerations

Surgical debridement is mandatory for necrotizing fasciitis, with return to the operating room every 24-36 hours until no further debridement is needed. 1

Indications for surgery include:

• No response to antibiotics after reasonable trial 1
• Profound toxicity, fever, hypotension, or advancement during antibiotic therapy 1
• Skin necrosis with easy fascial dissection 1
• Gas in affected tissue 1