Ceftriaxone for Streptococcal Infections
Ceftriaxone is highly effective for most streptococcal infections and serves as a first-line agent for severe cases, particularly Group B streptococcal endocarditis, and as a reasonable alternative to penicillin for Group A streptococcal infections and viridans group streptococci when penicillin cannot be used. 1, 2
Group B Streptococcal Infections
For Group B streptococcal endocarditis, use ceftriaxone 2 g IV/IM once daily for 4-6 weeks, with gentamicin 3 mg/kg/day added for the first 2 weeks. 1 This combination is critical because Group B streptococci produce abscesses and have high mortality rates, making the abbreviated 2-week endocarditis regimen inappropriate. 1
- For prosthetic valve endocarditis caused by Group B streptococci, extend treatment to 6 weeks and obtain early surgical consultation due to exceptionally high mortality. 1
- In neonatal GBS infections, use 25-50 mg/kg/day IV or IM in a single daily dose for 7 days (10-14 days if meningitis is documented). 1
Group A Streptococcal Infections (Pharyngitis)
For Group A streptococcal pharyngitis, first-line therapy should be amoxicillin or phenoxymethylpenicillin, with ceftriaxone reserved as a second-choice agent. 3 The WHO guidelines emphasize that most pharyngitis is viral and recommend watchful waiting as the initial approach. 3
- When antibiotics are indicated, penicillin-based therapy reduces rheumatic fever risk (RR 0.27; 95% CI 0.12-0.60) and suppurative complications. 3
- Cephalosporins show lower clinical relapse rates compared to penicillin (OR 0.55; 95% CI 0.31-0.99), though this advantage must be balanced against antimicrobial stewardship. 3
- A single intramuscular dose of ceftriaxone has demonstrated high efficacy in streptococcal pharyngitis, though clinical cure rates may be lower than 10-day oral therapy in some studies. 4
Viridans Group Streptococci and Endocarditis
For viridans group streptococcal endocarditis, ceftriaxone 2 g IV every 24 hours for 4-6 weeks is a reasonable alternative when penicillin cannot be used. 2 Use 4 weeks for native valve infections and 6 weeks for prosthetic valve infections. 2
- Critical caveat: 17% of viridans group streptococci may be resistant to ceftriaxone, so obtain susceptibility testing before relying on ceftriaxone monotherapy. 2
- Ceftriaxone has NO activity against enterococci—if enterococcal infection is suspected, switch to ampicillin or vancomycin plus gentamicin. 2
Streptococcus pneumoniae
For highly penicillin-susceptible S. pneumoniae causing endocarditis, ceftriaxone is reasonable as 4-week therapy for native valves or 6 weeks for prosthetic valves. 2 However, penicillin-resistant strains (MIC >0.1 mcg/mL) may show cross-resistance to ceftriaxone. 2
- In community-acquired pneumonia, ceftriaxone covers S. pneumoniae effectively, including many penicillin-resistant strains. 5, 6
- For severe otitis media, ceftriaxone is categorized as a Watch antibiotic and reserved for severe cases where amoxicillin or amoxicillin-clavulanate has failed. 3
FDA-Approved Indications
The FDA label confirms ceftriaxone is indicated for infections caused by susceptible streptococcal species, including: 5
- Lower respiratory tract infections (S. pneumoniae)
- Skin and soft tissue infections (S. pyogenes, viridans group streptococci)
- Bacterial septicemia (S. pneumoniae)
- Bone and joint infections (S. pneumoniae)
- Meningitis (S. pneumoniae)
Practical Dosing Summary
- Adults with serious streptococcal infections: 2 g IV/IM once daily 1, 2, 5
- Pediatric patients: 100 mg/kg/day IV in 1 dose (maximum 4 g/day) 1
- Neonatal GBS: 25-50 mg/kg/day IV or IM once daily 1
- Endocarditis: Add gentamicin for first 2 weeks when treating Group B streptococci 1
Key Clinical Pearls
- Ceftriaxone's long half-life (6.5 hours) allows once-daily dosing, improving convenience and potentially reducing costs. 6
- The drug achieves excellent tissue penetration, including CSF in the presence of inflammation. 6, 7
- For optimal efficacy, the free AUIC (area under the inhibitory curve) should be at least 125, which supports 1 g daily for infections where MIC values are below 2 mg/L. 7
- Always obtain susceptibility testing, as resistance patterns vary—particularly important for viridans group streptococci where resistance can reach 17-42%. 2