Streptococcus do grupo anginosus (S. anginosus, constellatus, intermedius)
Gram-positive cocci in short chains
Identification & Growth
Identification
- Tiny colonies with a characteristic butterscotch/caramel odour
- Variable hemolysis (alpha, beta or none); Lancefield antigen A, C, F or G
Growth Conditions
- Blood agar with 5% CO₂, 24–48 h; colonies < 0.5 mm
Clinical Significance
- Abscess formation — liver, brain, lung, head and neck
- Empyema and odontogenic infection
Intrinsic Resistance
- Aztreonam, colistin, nalidixic acid and aminoglycosides alone have no activity
Bench Alerts
- Isolation from deep material indicates abscess formation: alert the clinical team
- Do not lump with ordinary viridans streptococci — the species changes surgical management
Clinical Notes
Clinical presentations
- The anginosus group is strongly associated with deep pyogenic abscess formation, including brain, liver, and lung abscesses.
- Causes pleural empyema and mediastinitis, frequently in polymicrobial infections.
- Can cause infective endocarditis and bacteremia associated with gastrointestinal malignancies.
- Involved in odontogenic and head and neck infections.
Specimens and collection
- Image-guided abscess aspirate is the specimen of choice, collected in an anaerobic transport vial.
- Blood cultures should be drawn before antimicrobial initiation when bacteremia is suspected.
- Culture should include prolonged incubation and CO2-enriched atmosphere, as growth may be slow.
Epidemiology and at-risk populations
- Part of the human oral, gastrointestinal, and genital microbiota.
- Patients with periodontal disease, colorectal malignancy, or immunosuppression have increased risk of invasive infection.
- Bacteremia due to this group should prompt investigation for an occult abdominal source.
Resistance and therapeutic implications
- Generally penicillin-susceptible, which remains the treatment of choice for uncomplicated infections.
- Macrolide and clindamycin resistance is reported and should be individually tested.
- Abscess drainage is essential and often indispensable to therapeutic success, independent of antibiotic therapy.
Bench and reporting notes
- Small colonies with a characteristic butterscotch/caramel odor aid presumptive recognition on blood agar.
- Species-level identification within the group by MALDI-TOF or sequencing is recommended for clinical correlation.
- Report blood culture isolation as potentially significant, given lower contamination potential compared with viridans streptococci.
Sources
- PubMed — Streptococcus anginosus group clinical review
- EUCAST — Clinical breakpoints
- CDC — Streptococcal disease
Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.
FAQ: Frequently Asked Questions
How to identify Streptococcus do grupo anginosus (S. anginosus, constellatus, intermedius) in the lab?
Streptococcus do grupo anginosus (S. anginosus, constellatus, intermedius) is identified through tiny colonies with a characteristic butterscotch/caramel odour, variable hemolysis (alpha, beta or none); lancefield antigen a, c, f or g.
What are the intrinsic resistances of Streptococcus do grupo anginosus (S. anginosus, constellatus, intermedius)?
This organism is naturally resistant to aztreonam, colistin, nalidixic acid and aminoglycosides alone have no activity. These drugs should not be reported as susceptible.
Where is Streptococcus do grupo anginosus (S. anginosus, constellatus, intermedius) commonly found?
It is typically associated with abscess formation — liver, brain, lung, head and neck, empyema and odontogenic infection.
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