S sanguis
Reading File
Searching the Web
Streptococcus sanguinis microbiology clinical significance
Finding Sources
Searching PubMed
"Streptococcus sanguinis" endocarditis
Reading File
Reading File
Reading File
Here is a complete summary of Streptococcus sanguinis (also written S. sanguis):
Streptococcus sanguinis (S. sanguis)
Classification
- Gram-positive coccus, alpha-hemolytic (viridans group streptococcus)
- Part of the Streptococcus sanguinis group within the broader viridans streptococci
- Related species: S. gordonii, S. parasanguinis, S. cristatus
- Higher G+C content (~43.4%) than many other streptococci
Normal Habitat
- Commensal of the human oral cavity - one of the earliest colonizers of tooth surfaces and dental plaque
- Also found in the oropharynx
- Passed predominantly from mother to child during early life
Virulence & Pathogenesis
- Adhesins: Uses protein adhesins (SrtA-dependent surface proteins) to bind firmly to tooth enamel, restorative dental materials, and epithelial cells
- Biofilm formation: Participates in early dental plaque biofilm; its presence facilitates colonization by later, more pathogenic organisms
- Bacteremia: Dental procedures (scaling, extraction, etc.) can allow transient bacteremia; the organism then binds to damaged or abnormal cardiac endothelium
- IgA protease production: Proposed link to chronic infection and initiation of Adamantades-Behcet disease through antigen KTH-1
Clinical Significance
1. Infective Endocarditis (most important)
- Among the highest-risk viridans streptococci for developing endocarditis after bacteremia (along with S. mutans, S. gordonii, S. gallolyticus, S. mitis)
- Classic cause of subacute bacterial endocarditis (SBE) on previously abnormal native valves (rheumatic, bicuspid, MVP with regurgitation)
- Produces vegetations - fibrin-platelet aggregates with embedded bacteria
- Typical clinical course: low-grade fever, night sweats, weight loss, new murmur, embolic phenomena over weeks
- Associated with dental procedures as the portal of entry - Goldman-Cecil Medicine
2. Other Infections
- Catheter-related bloodstream infections
- Neutropenia-related bloodstream infections (immunocompromised patients)
- Purulent dental, abdominal, hepatobiliary, and brain infections
Duke Criteria Context
S. sanguinis bacteremia in the setting of a compatible clinical picture meets a major criterion (typical microorganism for endocarditis) in the Duke criteria for diagnosing infective endocarditis. - Quick Compendium of Clinical Pathology, 5th ed.
Treatment
Viridans streptococci including S. sanguinis:
- First-line: Penicillin G (if susceptible) - 4 million units IV every 4 hours
- Penicillin resistance is 30-50% in some areas, so empirical therapy usually starts with vancomycin (15-20 mg/kg IV twice daily) and de-escalates to a beta-lactam once susceptibility is confirmed
- For endocarditis: prolonged course (4-6 weeks), often with synergistic gentamicin in the first 2 weeks (for native valve endocarditis with susceptible organisms)
- Goldman-Cecil Medicine
Key Points for Exams
| Feature | Detail |
|---|---|
| Gram stain | Gram-positive cocci in chains |
| Hemolysis | Alpha (viridans) |
| Habitat | Oral cavity, dental plaque |
| Key disease | Subacute bacterial endocarditis |
| Predisposing valve lesion | Previously abnormal native valve |
| Entry route | Dental procedures -> transient bacteremia |
| Antibiotic of choice | Penicillin G (if susceptible); vancomycin if resistant |
| Associated condition | Behcet disease (proposed link via IgA protease/KTH-1 antigen) |
This is a shared conversation. Sign in to Orris to start your own chat.