From the Guidelines
Ceftriaxone is effective against Streptococcus agalactiae (Group B strep) and can be used as an alternative to penicillin G in patients who are allergic to penicillin or require broader coverage. The evidence from the 2015 ESC guidelines for the management of infective endocarditis 1 and the 2015 American Heart Association scientific statement on infective endocarditis in childhood 1 supports the use of ceftriaxone as a treatment option for streptococcal infections, including Group B strep. Some key points to consider when using ceftriaxone to treat Group B strep infections include:
- The typical adult dosing for serious Group B strep infections is 1-2 grams intravenously every 24 hours, with treatment duration typically ranging from 10-14 days depending on the site and severity of infection.
- Ceftriaxone works by binding to penicillin-binding proteins in the bacterial cell wall, inhibiting cell wall synthesis and causing bacterial cell death.
- It achieves high serum levels and has good tissue penetration, which contributes to its effectiveness against Group B strep.
- While ceftriaxone is effective against Group B strep, penicillin G remains the first-line therapy for Group B strep infections in non-allergic patients due to its narrower spectrum and lower cost.
- Ceftriaxone is an excellent alternative for penicillin-allergic patients or in situations requiring broader coverage, as seen in the treatment of infective endocarditis caused by penicillin-susceptible streptococci 1.
From the FDA Drug Label
At least 90 percent of the following microorganisms exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for ceftriaxone. However, the efficacy of ceftriaxone in treating clinical infections due to these microorganisms has not been established in adequate and well-controlled clinical trials Gram-positive bacteria Streptococcus agalactiae
Ceftriaxone may be effective against Streptococcus agalactiae (Group B strep) based on in vitro data, but its clinical efficacy has not been established in treating infections caused by this microorganism 2.
From the Research
Ceftriaxone Coverage of Streptococcus agalactiae (Group B Strep)
- Ceftriaxone has been shown to be effective against Streptococcus agalactiae (Group B strep) in various studies 3, 4, 5.
- The minimal inhibitory concentrations (MICs) of ceftriaxone against Group B strep have been reported to be 0.05-0.1 mg/l, and the minimal bactericidal concentrations (MBCs) have been reported to be 0.1-0.4 mg/l 3.
- Ceftriaxone has been shown to be effective in treating Group B strep infections in infant rats, with all treated animals surviving and both CSF and blood remaining sterile after treatment 3.
- However, a more recent study found that ceftriaxone-non-susceptible Group B strep isolates occur at relatively high rates in Japan, particularly among isolates with reduced penicillin susceptibility (PRGBS) 6.
Mechanism of Action and Resistance
- Ceftriaxone is a third-generation cephalosporin with a broad spectrum of activity against Gram-positive and Gram-negative bacteria 4.
- The mechanism of action of ceftriaxone involves inhibiting cell wall synthesis in bacteria, ultimately leading to cell lysis and death 4.
- Resistance to ceftriaxone can occur through various mechanisms, including the production of beta-lactamases that inactivate the antibiotic 6.
Clinical Implications
- Ceftriaxone is commonly used to treat a variety of bacterial infections, including those caused by Streptococcus agalactiae (Group B strep) 4, 7.
- However, the emergence of ceftriaxone-non-susceptible Group B strep isolates highlights the need for careful consideration of antibiotic choice and efficacy in treating these infections 6.
- Clinicians should be aware of the potential for resistance and monitor for signs of treatment failure or resistance when using ceftriaxone to treat Group B strep infections 6.