Gram-positive bacteria

• Bacteria that have a thick peptidoglycan layer in the cell wall and therefore stain purple on Gram stain

Organisms

• Cocci
  • Clusters/groups (staphylococcal species)
    • Catalase-positive
      • Coagulase-positive
        • Staphylococcus aureus
      • Coagulase-negative
        • Staphylococcus epidermidis
        • Staphylococcus saprophyticus
        • Staphylococcus lugdenensis
  • Chains/pairs (streptococcal and enterococcal species)
    • Catalase-negative
      • Streptococci
        • Alpha-hemolytic: partial hemolysis
          • S. pneumoniae
          • Viridans group
            • Milleri group
              • S. anginosus
        • Beta-hemolytic: complete hemolysis
          • Group A (S. pyogenes)
          • Group B (S. agalactiae)
          • Group C-H
        • Gamma-hemolytic: no hemolysis
          • S. bovis
      • Enterococci
        • E. faecalis
        • E. faecium
• Bacilli
  • Spore-forming
    • Anaerobic
      • Clostridioides difficile (diarrhea)
      • Clostridium perfringens (gas gangrene)
      • Clostridium tetani (tetanus)
      • Clostridium botulinum (botulism)
    • Aerobic
      • Bacillis anthracis (anthrax)
      • Bacillis cereus (food poisoning)
  • Non-spore-forming
    • Anaerobic
      • Cutibacterium acnes
    • Aerobic
      • Listeria monocytogenes (food poisoning) (small and motile)
      • Corynebacterium diphthereae (diphtheria)
  • Weakly acid-fast
    • Nocardia
    • Actinomyces
• Anaerobes
  • Clostridium
  • Peptostreptococcus
  • Cutibacterium acnes