[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Streptococci and enterococci](https://durgical.com/en/microbiology/groups/streptococci-and-enterococci/) › Streptococcus dysgalactiae # Streptococcus dysgalactiae - Bacterium ## Gram-positive? Thick peptidoglycan wall: stains purple. - For completeness A cousin of the strep throat bacterium that causes sore throat, cellulitis and bloodstream infection, mostly in older or sick adults. Updated Nov 13, 2026 Also called: group C and G streptococci, S. dysgalactiae subsp. equisimilis (SDSE) ## Quick facts **Type** Bacterium · [Streptococci and enterococci](https://durgical.com/en/microbiology/groups/streptococci-and-enterococci/) **Gram / shape** Gram-positive · Cocci in chains **Spread** Carried on skin and in the throat **Causes** Cellulitis and erysipelas · Bacteraemia **Treatment** Treated like group A On this page - The basics Key points - At a glance - Morphology - Transmission - Memory aid - What the colours mean - Clinical Virulence factors - Diseases it causes - Clinical picture - Diagnosis - Treatment Treatment - Prevention - Study Test yourself - Connections Connections ## Key points - Beta-haemolytic, large colonies, group C or G: S. dysgalactiae. - Shares M protein and streptolysins with group A and causes the same infections. - Leading cause of recurrent leg cellulitis and bacteraemia in older adults with comorbidities. - Penicillin is the drug of choice. ## At a glance **Gram** Gram-positive **Shape** Cocci in chains **Oxygen** Facultative anaerobe **Family** Streptococcaceae **Size** Large beta-haemolytic colonies like group A ## Morphology - Gram-positive cocci in chains; catalase-negative - Beta-haemolytic large colonies that look like Streptococcus pyogenes - Carries Lancefield group C or G antigen (rarely A or L) ## Transmission - Carried on skin and in the throat; enters through skin breaks - Respiratory droplets for pharyngitis; foodborne pharyngitis outbreaks have occurred - Animal-linked group C species (S. equi subsp. zooepidemicus) come from horses and unpasteurised milk **Reservoir:** Human skin, throat, gut and genital tract; animals for some group C species ### Isolation precautions What the care team adds to standard precautions. - Standard ## Virulence factors - M protein that resists phagocytosis, as in group A - Streptolysins and streptokinase - Some lineages are especially invasive ## Diseases it causes - Pharyngitis indistinguishable from group A strep throat [Streptococcal pharyngitis →](https://durgical.com/en/conditions/streptococcal-pharyngitis/) - Cellulitis and erysipelas, often recurrent in legs with lymphoedema or venous disease [Cellulitis of the leg →](https://durgical.com/en/conditions/cellulitis-of-the-leg/) - Bacteraemia, usually from a skin source [Sepsis and septic shock →](https://durgical.com/en/conditions/sepsis-and-septic-shock/) - Septic arthritis, including prosthetic joints [Septic Arthritis of the Knee →](https://durgical.com/en/conditions/septic-arthritis-of-the-knee/) - Infective endocarditis [Infective endocarditis →](https://durgical.com/en/conditions/infective-endocarditis/) - Necrotizing fasciitis and streptococcal toxic shock syndrome [Necrotizing soft tissue infection (necrotizing fasciitis, gas gangrene) →](https://durgical.com/en/conditions/necrotizing-soft-tissue-infection/) ## Clinical picture - Typical patient: older adult with diabetes, cancer, skin breakdown or chronic oedema - Recurrent leg cellulitis - Raw-milk outbreaks of S. zooepidemicus have caused post-streptococcal glomerulonephritis ## Diagnosis - Blood, tissue or joint culture; beta-haemolysis and Lancefield grouping - Throat culture identifies it; rapid group A antigen tests usually do not detect it - MALDI-TOF mass spectrometry to species ## Treatment Treated like group A: penicillin is the drug of choice, with cephalosporins as alternatives and clindamycin added in toxin-mediated severe disease. Macrolide, clindamycin and tetracycline resistance varies by region, so test isolates; surgery for necrotizing infection. Drug class only; doses and regimens are set by the clinician from the current guideline. In Pharmacology: - [Benzylpenicillin (penicillin G)](https://durgical.com/en/pharmacology/benzylpenicillin/) - [Amoxicillin](https://durgical.com/en/pharmacology/amoxicillin/) - [Cefazolin](https://durgical.com/en/pharmacology/cefazolin/) - [Clindamycin](https://durgical.com/en/pharmacology/clindamycin/) ## Prevention - Skin care and treatment of foot fungal infection and leg oedema to prevent recurrent cellulitis - Pasteurisation of milk - No vaccine ## Memory aid «Group A's older sibling»: same weapons, same infections, but it prefers grandparents with swollen legs. ## Test yourself Think of the answer, then tap the question to see it. ## Which species is the main human pathogen among group C and G streptococci? Streptococcus dysgalactiae subsp. equisimilis. ## Which virulence factors does S. dysgalactiae share with group A streptococcus? M protein, streptolysins and streptokinase. ## Which antibiotic is the drug of choice for group C and G streptococcal infection? Penicillin, as for group A. ## Why can a rapid strep test be negative in group C or G pharyngitis? Rapid tests detect the group A antigen, which these strains usually do not carry. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/streptococcus-dysgalactiae/) ## What the colours mean **Gram-positive** Thick peptidoglycan wall: stains purple. **Gram-negative** Thin wall with an outer membrane: stains pink. **Acid-fast** Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain. ## Connections ## Related 4 - [Streptococcus pyogenes](https://durgical.com/en/microbiology/streptococcus-pyogenes/) - [Streptococcus agalactiae](https://durgical.com/en/microbiology/streptococcus-agalactiae/) - [Streptococcus anginosus group](https://durgical.com/en/microbiology/streptococcus-anginosus-group/) - [Staphylococcus aureus](https://durgical.com/en/microbiology/staphylococcus-aureus/) ## Related conditions 6 - [Streptococcal pharyngitis](https://durgical.com/en/conditions/streptococcal-pharyngitis/) - [Cellulitis of the leg](https://durgical.com/en/conditions/cellulitis-of-the-leg/) - [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/) - [Septic Arthritis of the Knee](https://durgical.com/en/conditions/septic-arthritis-of-the-knee/) - [Infective endocarditis](https://durgical.com/en/conditions/infective-endocarditis/) - [Necrotizing soft tissue infection (necrotizing fasciitis, gas gangrene)](https://durgical.com/en/conditions/necrotizing-soft-tissue-infection/) [← Back to the group: Streptococci and enterococci](https://durgical.com/en/microbiology/groups/streptococci-and-enterococci/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Infections Caused by Group C and G Streptococcus (Streptococcus dysgalactiae subsp. equisimilis and Others): Epidemiological and Clinical Aspects](https://pmc.ncbi.nlm.nih.gov/articles/PMC11590429/) (Microbiology Spectrum (ASM), 2019); [Streptococcal Infections - Infectious Disease - MSD Manual Professional Edition](https://www.msdmanuals.com/professional/infectious-diseases/gram-positive-cocci/streptococcal-infections) (MSD Manual Professional Edition, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/microbiology/streptococcus-dysgalactiae/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/streptococcus-dysgalactiae/