Part 1 obgyn notes Sri Lanka
    NOTES for part 1
    /
    Microbiology
    /
    BACTERIAL CLASSIFICTION

    BACTERIAL CLASSIFICTION

    Owner
    U
    Untitled
    Verification
    Tags

    ⭐ THE 20% THAT GIVES 80% MARKS (SUPER HIGH-YIELD)

    1. First divide bacteria by Gram stain:
      • Gram-positive (purple)
      • Gram-negative (pink)
      • Atypical (no cell wall or poor staining)
    2. Gram-positive bacteria
      • Cocci:
        • Staphylococcus (clusters)
        • Streptococcus (chains)
        • Enterococcus (pairs)
      • Bacilli:
        • Spore-forming (Bacillus, Clostridium)
        • Non–spore-forming (Listeria, Corynebacterium)
    3. Gram-negative bacteria
      • Cocci: Neisseria
      • Bacilli:
        • Enteric (E. coli, Klebsiella, Salmonella, Shigella)
        • Respiratory (H. influenzae, Bordetella)
        • Zoonotic (Brucella, Francisella, Yersinia)
    4. Atypical bacteria
      • No cell wall: Mycoplasma, Ureaplasma
      • Weak wall: Chlamydia
      • Acid-fast: Mycobacteria
    5. Oxygen requirement classification
      • Obligate aerobes: Mycobacterium, Pseudomonas
      • Obligate anaerobes: Clostridium, Bacteroides
      • Facultative anaerobes: Enterobacteriaceae
    6. Shape classification
      • Cocci (spherical)
      • Bacilli (rod)
      • Spiral (spirochetes: Treponema, Borrelia)
    7. Special stains
      • Acid-fast: Mycobacterium
      • Silver stain: Legionella
      • India ink: Cryptococcus
    8. Wall components as classification
      • Gram-positive have thick peptidoglycan + teichoic acid
      • Gram-negative have outer membrane + LPS (endotoxin)

    If you know these → you can classify 99% of all bacteria in exams.

    🔬 FULL DETAILED CLASSIFICATION — CLEAR & COMPLETE

    1️⃣ BY GRAM STAIN

    A. Gram-positive (purple)

    1. Cocci

    • Clusters (grapes) → Staphylococcus
      • Coagulase + → S. aureus
      • Coagulase – → S. epidermidis, S. saprophyticus
    • Chains (strings) → Streptococcus
      • α-hemolysis → S. pneumoniae, viridans strep
      • β-hemolysis → S. pyogenes, S. agalactiae
      • γ-hemolysis → Enterococcus

    2. Bacilli (rods)

    • Spore-forming
      • Aerobic → Bacillus anthracis, B. cereus
      • Anaerobic → Clostridium tetani, botulinum, perfringens, difficile
    • Non–spore-forming
      • Corynebacterium diphtheriae
      • Listeria monocytogenes
      • Nocardia (weakly acid-fast)

    2️⃣ BY GRAM-NEGATIVE BACTERIA

    A. Cocci

    • Neisseria gonorrhoeae
    • Neisseria meningitidis
    • Moraxella catarrhalis

    B. Bacilli (Rods)

    1. Enteric Gram-negatives (enterobacteriaceae)

    • E. coli
    • Klebsiella
    • Proteus
    • Salmonella
    • Shigella
    • Enterobacter
    • Serratia
    • Yersinia

    2. Fastidious respiratory organisms

    • Haemophilus influenzae
    • Bordetella pertussis
    • Legionella pneumophila

    3. Curved rods

    • Vibrio cholerae
    • Campylobacter jejuni
    • Helicobacter pylori

    4. Zoonotic Gram-negatives

    • Brucella
    • Francisella tularensis
    • Pasteurella
    • Bartonella

    5. Anaerobes

    • Bacteroides fragilis

    3️⃣ ATYPICAL BACTERIA (DO NOT STAIN WELL)

    A. No cell wall

    • Mycoplasma pneumoniae
    • Ureaplasma urealyticum

      • → Resistant to β-lactam antibiotics.

    B. Poorly staining intracellular organisms

    • Chlamydia trachomatis
    • Chlamydophila pneumoniae
    • Rickettsia
    • Ehrlichia, Anaplasma

    C. Acid-fast bacteria

    • Mycobacteria (TB, leprosy)
    • Weakly acid-fast: Nocardia

    4️⃣ BY SHAPE

    Cocci (spheres)

    • Staph, Strep, Enterococcus, Neisseria

    Bacilli (rods)

    • Clostridium
    • Bacillus
    • Corynebacterium
    • Listeria
    • Enterobacteriaceae

    Spiral

    • Spirochetes:
      • Treponema pallidum
      • Borrelia burgdorferi
      • Leptospira

    Comma-shaped

    • Vibrio
    • Campylobacter
    • Helicobacter

    5️⃣ BY OXYGEN REQUIREMENTS

    Obligate aerobes

    Always need oxygen

    • Mycobacterium tuberculosis
    • Pseudomonas
    • Nocardia

    Obligate anaerobes

    Killed by oxygen

    • Clostridium
    • Bacteroides
    • Actinomyces

    Facultative anaerobes

    Can live with or without oxygen

    • Enterobacteriaceae
    • Staphylococci
    • Streptococci

    Microaerophilic

    • Campylobacter
    • Helicobacter

    6️⃣ BY SPORE FORMATION

    Gram-positive spore formers

    • Bacillus
    • Clostridium

      • (These survive harsh environments.)

    7️⃣ BY ENERGY/LOCATION

    Intracellular bacteria

    Obligate intracellular

    • Chlamydia
    • Rickettsia

    Facultative intracellular

    • Listeria
    • Salmonella
    • Mycobacteria
    • Brucella
    • Legionella

    8️⃣ BY SPECIAL STAINING TECHNIQUES

    • Acid-fast → Mycobacteria, Nocardia
    • Silver stain → Legionella
    • India ink → Cryptococcus (fungus)
    • Giemsa stain → Chlamydia, Borrelia, Rickettsia
    • Endospore stain → Bacillus, Clostridium

    🎯 THE MUST-MEMORISE CLASSIFICATION SUMMARY

    1. First divide into Gram-positive, Gram-negative, Atypical.
    2. Gram-positive cocci: Staph (clusters), Strep (chains).
    3. Gram-positive rods: Bacillus, Clostridium (spores); Listeria, Corynebacterium (no spores).
    4. Gram-negative cocci: Neisseria.
    5. Gram-negative rods: Enterics, respiratory, zoonotic, curved rods.
    6. Atypical: Mycoplasma, Chlamydia, Rickettsia, Mycobacteria.
    7. Oxygen: aerobes (TB), anaerobes (Clostridium), facultative (enterics).
    8. Shape: cocci, rods, spiral.
    9. Key stains: acid-fast (TB), silver (Legionella), Giemsa (Chlamydia).
    10. Spores: Bacillus & Clostridium only.