Gram-positive bacteria

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
    - Clostridium dificile (diarrhea)
    - Clostridium perfringens (gas gangrene)
    - Clostridium tetani (tetanus)
    - Clostridium botulinum (botulism)
  - Aerobic
    - Bacillis anthracis (anthrax)
    - Bacillis cereus (food poisoning)
- Non-spore-forming
  - Anaerobic
    - Propionibacterium acnes
  - Aerobic
    - Listeria monocytogenes (food poisoning) (small and motile)
    - Corynebacterium diphthereae (diphtheria)
- Weakly acid-fast
  - Nocardia
  - Actinomyces
Anaerobes
- Clostridium
- Peptostreptococcus
- Propionibacterium acnes