From the Guidelines
Penicillin G is the preferred antibiotic for treating strep viridans infections, with a recommended dosage of 12-18 million U/day i.v. either in 4-6 doses or continuously for 4 weeks, as stated in the 2015 ESC guidelines 1. The choice of antibiotic depends on the severity of the infection and the patient's renal function.
- For patients with normal renal function, penicillin G or amoxicillin can be used as a standard treatment for 4 weeks 1.
- For patients with impaired renal function, penicillin G is preferred due to its better safety profile 1.
- In cases of beta-lactam allergy, vancomycin can be used as an alternative, with a recommended dosage of 30 mg/kg/day i.v. in 2 doses for 4 weeks 1.
- Ceftriaxone is also a viable option, with a recommended dosage of 2 g/day i.v. or i.m. in 1 dose for 4 weeks 1. It's essential to note that the duration of treatment may vary depending on the infection site and severity, and antibiotic susceptibility testing may be necessary in some cases to guide treatment decisions 1.
- The American Heart Association recommends aqueous crystalline penicillin G sodium as a first-line treatment for native valve endocarditis caused by viridans group streptococci, with a dosage of 24 million U/24 h IV either continuously or in 4-6 equally divided doses for 4 weeks 1.
- Vancomycin hydrochloride is recommended as an alternative for patients who are unable to tolerate penicillin or ceftriaxone therapy, with a dosage of 30 mg/kg per 24 h IV in 2 equally divided doses for 4 weeks 1.
From the FDA Drug Label
Clinical Indication Dosage Serious infections, such as pneumonia and endocarditis, due to susceptible strains of streptococci (including S pneumoniae) and meningococcus 150,000 - 300,000 units/kg/day divided in equal doses every 4 to 6 hours; duration depends on infecting organ-ism and type of infection Penicillin G is highly active in vitro against streptococci (groups A, B, C, G, H, L, and M)
Penicillin G is a good antibiotic for strep viridans, as it is highly active in vitro against streptococci. The recommended dosage for serious infections, such as endocarditis, due to susceptible strains of streptococci is 150,000 - 300,000 units/kg/day divided in equal doses every 4 to 6 hours 2.
From the Research
Antibiotics for Strep Viridans
- Ceftriaxone and penicillin G are considered reasonable treatment options for viridans group streptococci (VGS) bloodstream infections 3
- Penicillin or Ceftriaxone is the recommended first line agent for definitive therapy of VGS endocarditis 4
- The susceptibility rates for S. sanguis were: penicillin, 74%; amoxicillin, 84%; ceftriaxone, 94%; clindamycin, 87%, and vancomycin, 100% 5
- S. mitis/oralis group showed the lowest susceptibilities to betalactam antibiotics among all speciated and non speciated VGS 4
- High level resistance (MIC > or = 2 mg/l) to ceftriaxone was found in 12 isolates, comprising S. oralis (n = 7), S. mitis (n = 4) and S. parasanguis (n = 1) 6
- Cumulative susceptibility rates across all years were similar between species for ceftriaxone (range: 96.0% to 100%), clindamycin (81.3% to 84.5%), and vancomycin (99.7% to 100%) 7
Resistance Patterns
- Penicillin resistant isolates (MIC > or = 2 mg/l) also demonstrated decreased susceptibility to other antimicrobial agents tested 6
- Susceptibility rates for some clinically relevant antibiotics declined between 2010 and 2020, highlighting the need to improve antimicrobial stewardship efforts 7
- The emergence of resistance to betalactam agents like penicillin will only narrow available therapeutic options and further challenge the treatment of VGS infections 4