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🔬 2nd MBBS MICROBIOLOGY - MUHS EXAM NOTES

(Apurb Shastri Pattern | Colour-Coded | Exam Ready)

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UNIT 1: STERILIZATION & DISINFECTION

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📌 LAQ 1: STERILIZATION AND DISINFECTION

🔷 DEFINITIONS (★★★ Most Important for MUHS)

Exam Tip: Sterilization is an ABSOLUTE term - it means killing ALL organisms including spores. Disinfection is RELATIVE.

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🔷 ENUMERATE METHODS OF STERILIZATION

METHODS OF STERILIZATION
├── A. PHYSICAL METHODS
│   ├── 1. HEAT
│   │   ├── DRY HEAT
│   │   │   ├── Red heat (incineration)
│   │   │   ├── Flaming
│   │   │   ├── Hot Air Oven (160°C/1 hr or 180°C/30 min)
│   │   │   └── Incineration
│   │   └── MOIST HEAT
│   │       ├── Boiling (100°C)
│   │       ├── Pasteurization (62°C/30 min or 72°C/15 sec)
│   │       ├── Autoclave (steam under pressure - 121°C/15 min)
│   │       ├── Tyndallization (Fractional sterilization)
│   │       └── Inspissation
│   ├── 2. RADIATION
│   │   ├── Ionizing (Gamma rays, X-rays)
│   │   └── Non-ionizing (UV light)
│   ├── 3. FILTRATION
│   │   ├── Seitz filter (asbestos)
│   │   ├── Berkefield filter (diatomite)
│   │   ├── Chamberland filter (porcelain)
│   │   └── Membrane filter (0.22 µm)
│   └── 4. ULTRASONIC WAVES
│
└── B. CHEMICAL METHODS
    ├── Gases: Ethylene oxide, Formaldehyde gas, Beta-propiolactone
    └── Liquids: Glutaraldehyde, Hydrogen peroxide, Halogens, Phenols

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🔴 DRY HEAT STERILIZATION

Methods of Dry Heat:

1. Red Heat - Inoculation loop/wire held in Bunsen flame until red hot
2. Flaming - Passed through Bunsen flame (scalpels, forceps, mouth of culture tubes)
3. Hot Air Oven - Most common dry heat sterilization method
4. Incineration - Burning of infected material (carcasses, contaminated dressings)

Mechanism of Dry Heat:

• Acts by oxidation of cell constituents
• Causes protein denaturation and destruction of microbial DNA

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🔴 HOT AIR OVEN (★★★ MUHS Favourite)

Principle:

• Destroys microorganisms by oxidation and denaturation of proteins using dry heat
• Dry heat is less efficient than moist heat (no penetration by steam), so higher temperature and longer time are needed

Working / Operating Conditions:

Diagram of Hot Air Oven:

┌─────────────────────────────────┐
│         HOT AIR OVEN            │
│  ┌───────────────────────────┐  │
│  │   INNER CHAMBER           │  │
│  │  ┌─────────────────────┐  │  │
│  │  │ ←← Air Circulation  │  │  │
│  │  │    Shelves with      │  │  │
│  │  │    articles          │  │  │
│  │  │    (wrapped in       │  │  │
│  │  │     kraft paper)     │  │  │
│  │  └─────────────────────┘  │  │
│  │   Electric Heating Coils  │  │
│  └───────────────────────────┘  │
│    Thermometer / Thermostat      │
│    Outer insulated shell         │
└─────────────────────────────────┘

Role in Sterilization:

• Sterilizes materials that would be damaged by moisture
• Items must be dry before loading (moisture prevents effective heat penetration)
• Items wrapped in kraft (brown) paper - NOT newspaper
• Loading: should not be overcrowded (needs air circulation)
• After sterilization: oven cooled to 60°C before opening (prevents cracking of glassware)

Items Sterilized in Hot Air Oven:

• Glassware (Petri dishes, flasks, pipettes, syringes)
• Swabs, cotton, dressings
• Forceps, scissors (dry metal instruments)
• Liquid paraffin, oils, waxes, powders (cannot be autoclaved)
• Rubber goods - NOT suitable (will be damaged)

Advantages:

• No moisture, no rusting
• Suitable for heat-stable substances that cannot tolerate steam

Disadvantages:

• Higher temperature, longer time required
• Cannot sterilize rubber, plastic, liquids

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🔴 AUTOCLAVE (★★★★ Most Important in MUHS)

Definition:

Principle (★★★):

• Water boils at 100°C at atmospheric pressure
• Under increased pressure, the boiling point of water RISES
• At 15 lbs/inch² (1 atm above atmospheric) = 121°C for 15 minutes - kills ALL organisms including spores
• Moist heat kills by coagulation and denaturation of proteins
• Steam penetrates materials far better than dry heat
• Latent heat of condensation adds extra killing power

Why Moist Heat is Superior to Dry Heat:

• Proteins coagulate at much lower temperatures when WET
• Steam penetrates better
• Latent heat of condensation releases energy directly onto organisms

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Types of Autoclave:

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Applications (★★):

• Sterilization of culture media
• Surgical instruments, gowns, drapes, gloves
• Liquid media (broth)
• Contaminated laboratory waste before disposal

FOUR ITEMS STERILIZED IN AUTOCLAVE (★★):

1. Culture media (nutrient agar, broth)
2. Surgical instruments (metal, rubber)
3. Surgical linen (gowns, drapes, towels)
4. Gloves and rubber materials

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Working of Autoclave:

AUTOCLAVE - WORKING STEPS
┌─────────────────────────────────────────────┐
│ 1. Load articles into chamber               │
│ 2. Close and clamp the door (seal)          │
│ 3. Heat water reservoir (electric/steam)    │
│ 4. Open air vent - allow air to escape      │
│    (air removal is CRITICAL - air pockets   │
│     reduce temperature and kill efficiency) │
│ 5. Close vent once steam flows freely       │
│ 6. Pressure builds to 15 lbs/inch²          │
│    → Temperature reaches 121.6°C            │
│ 7. Maintain for 15 minutes (exposure time)  │
│ 8. Turn off heat                            │
│ 9. Allow pressure to fall to zero slowly    │
│    (sudden release → boiling of liquids)    │
│ 10. Open door slightly, allow drying/cooling│
│ 11. Remove items - check autoclave tape     │
└─────────────────────────────────────────────┘

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Diagram of Autoclave:

           ┌──────────────────────────────────┐
           │         AUTOCLAVE                │
           │   Safety Valve   Pressure Gauge  │
           │       ↑               ↑          │
           │  ┌────────────────────────────┐  │
           │  │   STEAM UNDER PRESSURE     │  │
           │  │                            │  │
           │  │   Articles on Shelf/Tray   │  │
           │  │   ┌──────────────────┐     │  │
           │  │   │  INNER CHAMBER   │     │  │
           │  │   └──────────────────┘     │  │
           │  │                            │  │
           │  └────────────────────────────┘  │
           │   Steam inlet        Air/Water   │
           │   from boiler ──→    outlet ──→  │
           │   ┌──────────────────────────┐   │
           │   │  WATER/STEAM GENERATOR   │   │
           │   │  (Electric heating coils)│   │
           │   └──────────────────────────┘   │
           │   Thermometer   Door lock/clamp  │
           └──────────────────────────────────┘

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Operational Complications (★★):

Quality Control of Autoclave:

• Physical: Thermometer, pressure gauge
• Chemical: Autoclave tape (brown diagonal lines appear), Browne's tube (green = sterile)
• Biological: Bacillus stearothermophilus (spores) - gold standard

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🔴 MOIST HEAT STERILIZATION - ENUMERATE METHODS (★★):

MOIST HEAT STERILIZATION
├── 1. Below 100°C
│   ├── Pasteurization (62°C/30 min or 72°C/15 sec)
│   └── Inspissation (80-85°C / 30 min × 3 days - Lowenstein Jensen media)
│
├── 2. At 100°C
│   ├── Boiling (100°C/10-30 min - kills vegetative forms)
│   └── Tyndallization / Fractional sterilization (100°C/30 min × 3 consecutive days)
│
└── 3. Above 100°C (Steam under pressure)
    └── Autoclave (121°C / 15 min / 15 lbs/inch²)

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SAQ 1: GASEOUS DISINFECTANTS

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Definition:

Important Gaseous Disinfectants:

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🔸 1. ETHYLENE OXIDE (ETO) (★★★ Most Important)

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🔸 2. FORMALDEHYDE GAS (★★)

• Formalin 150 mL + KMnO₄ 450 g per 1000 cubic feet of room space
• Room sealed for 24 hours, then ventilated for 24 hours

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🔸 3. BETA-PROPIOLACTONE (BPL)

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🔸 4. VAPOR-PHASE HYDROGEN PEROXIDE (VPHP)

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🔸 5. OZONE

• Powerful oxidizing agent; destroys vegetative bacteria, viruses, and spores
• Used in water treatment and air disinfection
• Unstable at room temperature

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Summary Table - Gaseous Disinfectants:

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SAQ 2: TYNDALLISATION

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Definition:

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Principle (★★★):

DAY 1 → Heat at 100°C for 30 min
         → Kills all VEGETATIVE forms
         → Spores SURVIVE
         ↓ Incubate at 37°C overnight
         → Surviving spores GERMINATE into vegetative forms
         
DAY 2 → Heat at 100°C for 30 min
         → Kills newly germinated vegetative forms
         → Any remaining spores survive
         ↓ Incubate at 37°C overnight
         → Remaining spores germinate
         
DAY 3 → Heat at 100°C for 30 min
         → Kills all remaining vegetative forms
         → COMPLETE STERILIZATION ACHIEVED

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When is Tyndallization Used? (★★):

1. Culture media that cannot withstand autoclave temperatures - e.g., Serum media (Loeffler's serum slope), egg-containing media (LJ medium - but these use inspissation)
2. Media containing sugars/carbohydrates - heat-labile sugars are destroyed at autoclave temperatures; Tyndallization at 100°C preserves them
3. Gelatin media - melts/denatures at autoclave temperature
4. Any material that is heat-labile but CAN withstand 100°C

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Apparatus Used:

• Koch's or Arnold's steamer (generates flowing steam at 100°C without pressure)

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Limitations:

• Time-consuming (3 days)
• Does not reliably sterilize if spores fail to germinate (non-germinators remain)
• Not truly reliable for all spore-forming organisms
• Has largely been replaced by membrane filtration for heat-labile materials

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LAQ 2: CHEMICAL AGENTS FOR DISINFECTION

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FOUR IMPORTANT CHEMICAL DISINFECTANTS (★★★):

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1. 🔸 ALCOHOLS (Ethyl alcohol / Isopropyl alcohol)

• Concentration: 70% most effective (100% is less effective - requires water)
• Mechanism: Denaturation of proteins; disruption of cell membranes
• Uses: Skin antisepsis, disinfection of surfaces, thermometers, instruments
• Limitations: NO action on spores or non-enveloped viruses; evaporates rapidly; not suitable for open wounds

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2. 🔸 HALOGENS (Chlorine, Iodine)

• Chlorine: Strong oxidizing agent; used as bleaching powder (chlorination of water, disinfection of surfaces, floors)
• Iodine: Precipitates proteins and oxidizes essential enzymes
  • Tincture of iodine (2% iodine + 70% alcohol) - skin disinfection
  • Povidone-iodine (Betadine) - iodine + polyvinylpyrrolidone; used for surgical skin prep, wound care
• Limitations: Irritating to mucosa, stains, can cause allergy

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3. 🔸 PHENOLS AND PHENOLIC COMPOUNDS

• Examples: Phenol (carbolic acid - Lister used this first), Lysol, Dettol (chloroxylenol)
• Mechanism: Disrupt lipid-containing membranes → leakage of cellular contents; also denature proteins
• Uses: Disinfection of floors, walls, drains, bedpans, sputum discard jars
• Limitations: Not suitable for skin (toxic, corrosive); inactivated by organic matter

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4. 🔸 QUATERNARY AMMONIUM COMPOUNDS (QUATS)

• Examples: Benzalkonium chloride (Zephiran), Cetrimide, Cetylpyridinium chloride
• Mechanism: Cationic detergents - react with cell membrane lipids → alter membrane permeability → leakage of cell contents → death
• Uses: Skin antisepsis, disinfection of non-critical equipment (blood pressure cuffs, stethoscopes, floors)
• Limitations: Inactive against spores, mycobacteria, non-enveloped viruses; inactivated by soap/anionic detergents; adsorb to cotton

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(Other important ones to mention):

• Glutaraldehyde (2%): High-level disinfectant/sterilant; alkylating agent; used for endoscopes, respiratory therapy equipment
• Hydrogen Peroxide (3-6%): Oxidizing agent; contact lenses, wounds, surface disinfection

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PROPERTIES OF AN IDEAL DISINFECTANT (★★★):

IDEAL DISINFECTANT - MNEMONIC: "BROAD SCIENTIST"

1. Broad spectrum - effective against bacteria, fungi, viruses, spores
2. Rapid action - quick kill time
3. Organic matter - not inactivated by organic matter (pus, blood)
4. Affordable - low cost
5. Dilute solution - effective even in low concentrations
6. Stable - shelf-stable, long shelf life
7. Compatible - compatible with other agents
8. Innocuous - non-toxic to human tissues
9. Ease of use - easy preparation and application
10. No staining or odour
11. Transparent - so can see through solution
8. Independent of pH - effective at various pH levels
9. Surface-active - good penetration and wetting ability
10. Tasteless/odourless - for food surface disinfection

Phenol Coefficient: Ratio of dilution of disinfectant killing organisms in 10 min but NOT 5 min / dilution of phenol doing same = measure of disinfectant efficacy

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UNIT 2: CULTURE MEDIA

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📌 CLASSIFICATION OF CULTURE MEDIA (★★★):

CLASSIFICATION OF CULTURE MEDIA
│
├── A. Based on CONSISTENCY
│   ├── Solid (1.5-2% agar) - e.g., Blood agar, MacConkey agar
│   ├── Semi-solid (0.2-0.5% agar) - e.g., Motility media, Hugh & Leifson
│   └── Liquid / Broth (no agar) - e.g., Nutrient broth, Robertson's cooked meat
│
├── B. Based on COMPOSITION
│   ├── Simple/Basal media - Nutrient broth, Nutrient agar, Peptone water
│   ├── Enriched media - Blood agar, Chocolate agar, LJ media
│   ├── Enrichment media - Alkaline peptone water, Selenite F broth
│   ├── Selective media - MacConkey agar, TCBS agar, Lowenstein Jensen
│   ├── Differential media - MacConkey agar, CLED agar, Eosin methylene blue
│   ├── Indicator media - contains pH indicator (phenol red in MacConkey)
│   └── Transport media - Stuart's, Pike's, Buffered glycerol saline
│
└── C. Based on USE
    ├── General purpose - Nutrient agar
    ├── Special purpose - Blood culture broths
    └── Anaerobic media - Robertson's cooked meat, thioglycolate broth

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ENRICHED MEDIA - EXAMPLES (★★):

Media to which extra nutrients have been ADDED to support growth of fastidious organisms.

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SELECTIVE MEDIA - EXAMPLES (★★):

Media containing inhibitors that suppress unwanted organisms while allowing target organism to grow.

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📌 SAQ: ENRICHMENT MEDIA (★★★)

Definition:

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How Enrichment Media Works:

Specimen (e.g., stool with few Salmonella + lots of coliforms)
              ↓
Inoculate into ENRICHMENT BROTH
(e.g., Selenite F broth)
              ↓
Incubate 37°C / 6-18 hours
              ↓
Selenite INHIBITS coliforms (Klebsiella, E.coli)
Salmonella MULTIPLES freely
              ↓
Subculture onto MacConkey / Wilson & Blair
              ↓
Higher chance of isolating Salmonella

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Two Examples of Enrichment Media:

1. 🔸 SELENITE F BROTH

• Composition: Sodium selenite + peptone water
• Mechanism: Sodium selenite is toxic to coliforms (E. coli, Klebsiella) but Salmonella/Shigella are resistant
• Use: Stool specimens for isolation of Salmonella typhi, Salmonella paratyphi, Shigella
• Note: Must subculture within 12-18 hours as selenite becomes inhibitory to Salmonella with prolonged incubation

2. 🔸 ALKALINE PEPTONE WATER (APW)

• Composition: Peptone water at pH 8.6-9.0
• Mechanism: Alkaline pH inhibits most coliforms but Vibrio cholerae tolerates and rapidly multiplies in alkaline environment
• Use: Stool samples for isolation of Vibrio cholerae
• Incubation: 37°C for 6 hours, then subculture to TCBS agar

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How Enrichment Media DIFFERS from Enriched Media (★★★ MUHS Favourite):

Memory Tip: Enriched = ADD nutrients; Enrichment = SUPPRESS competition

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SOLID CULTURE MEDIA WITHOUT AGAR - TWO EXAMPLES (★★):

1. 🔸 LOWENSTEIN-JENSEN (LJ) MEDIUM

• Solidifying agent: Egg (coagulated by inspissation at 80°C)
• Use: Isolation of Mycobacterium tuberculosis
• Contains: Egg, glycerol, asparagine, mineral salts, malachite green (as inhibitor)

2. 🔸 LOEFFLER'S SERUM SLOPE

• Solidifying agent: Animal serum (horse/ox) - coagulated by inspissation
• Use: Primary isolation of Corynebacterium diphtheriae; shows metachromatic granules
• Contains: Blood serum + glucose broth (3:1 ratio)

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UNIT 3: EXOTOXINS vs ENDOTOXINS

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📌 FOUR DIFFERENCES: EXOTOXINS AND ENDOTOXINS (★★★★ MUHS Repeated)

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Extended Differences Table (For LAQ scoring):

Exam Tip for MUHS: "FOUR DIFFERENCES" means write at least 4 clearly labeled rows. Best approach = table format.

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UNIT 4: MODES OF TRANSMISSION

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📌 MODES OF TRANSMISSION OF INFECTIOUS AGENTS (Park's Textbook, Park's Preventive Medicine)

Classification:

MODES OF TRANSMISSION
│
├── A. DIRECT TRANSMISSION
│   ├── 1. Direct contact (touching, kissing, sexual contact)
│   ├── 2. Droplet infection (<3 feet range, >5 µm droplets)
│   ├── 3. Contact with soil / surface
│   ├── 4. Inoculation into skin or mucosa (needlestick, bite)
│   └── 5. Transplacental / Vertical transmission
│
└── B. INDIRECT TRANSMISSION
    ├── 1. Vehicle-borne (food, water, blood, air)
    ├── 2. Vector-borne (mechanical / biological)
    └── 3. Airborne (<5 µm droplet nuclei, travel >3 feet)

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A. DIRECT TRANSMISSION:

1. Direct Contact:

• Transfer requires physical contact between source and susceptible host
• Examples:
  • Skin-to-skin: Scabies, Ringworm, Impetigo
  • Sexual contact: Syphilis, Gonorrhea, HIV, HPV
  • Kissing: Herpes simplex, Mononucleosis
  • Animal bite: Rabies

2. Droplet Infection:

• Large droplets (>5 µm) expelled by coughing, sneezing, talking
• Settle quickly within 3 feet of the source
• Examples: Influenza, Pertussis, Meningitis (Meningococcal), Mumps, Plague

3. Contact with Soil:

• Infective agents survive in soil and penetrate skin
• Examples: Tetanus (C. tetani spores in soil), Hookworm (larvae penetrate bare feet), Anthrax

4. Inoculation:

• Direct injection into blood/tissues
• Examples: Needlestick (HIV, Hepatitis B/C), insect bite, tattoo needles

5. Transplacental (Vertical Transmission):

• Mother to fetus through placenta
• TORCH infections: Toxoplasma, Rubella, Cytomegalovirus, Herpes simplex
• Also: HIV, Syphilis, HBV

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B. INDIRECT TRANSMISSION:

1. Vehicle-Borne (Common Source):

• Explosive outbreak if contamination is heavy (cholera, Hepatitis A)
• Cases initially confined to those exposed to the vehicle
• Epidemic subsides when vehicle is controlled/removed

2. Vector-Borne:

• Diptera: Mosquitoes (Anopheles - malaria; Aedes - dengue/yellow fever; Culex - filariasis, Japanese encephalitis)
• Siphonaptera (Fleas): Plague (Xenopsylla cheopis)
• Anoplura (Lice): Typhus (Pediculus humanus)
• Acarina (Ticks/Mites): Scrub typhus (Trombiculid mite), Rocky Mountain spotted fever

3. Airborne Transmission:

• Droplet nuclei (<5 µm) remain suspended in air for prolonged periods and travel >3 feet
• Examples: Tuberculosis (M. tuberculosis), Measles, Chickenpox (Varicella), Q fever (Coxiella), Aspergillosis

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Diagram - Chain of Infection:

┌──────────────────────────────────────────┐
│            CHAIN OF INFECTION            │
│                                          │
│  RESERVOIR / SOURCE                      │
│  (Human, Animal, Soil, Water)            │
│          ↓                               │
│  PORTAL OF EXIT                          │
│  (Respiratory, GI, Skin, Blood, etc.)   │
│          ↓                               │
│  MODE OF TRANSMISSION                    │
│  (Direct / Indirect / Airborne)          │
│          ↓                               │
│  PORTAL OF ENTRY                         │
│  (Mouth, Lung, Skin, Conjunctiva)        │
│          ↓                               │
│  SUSCEPTIBLE HOST                        │
│  (Age, Immunity, Nutrition, Genetics)    │
└──────────────────────────────────────────┘

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UNIT 5: PATHOGENICITY AND VIRULENCE

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📌 LAQ: MICROBIAL PATHOGENICITY AND VIRULENCE

DEFINITIONS (★★★):

Virulence is measured by: LD₅₀ (lethal dose killing 50% of test animals) or ID₅₀ (infectious dose infecting 50%) Lower the LD₅₀ = HIGHER the virulence

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DETERMINANTS OF BACTERIAL VIRULENCE (★★★★):

VIRULENCE DETERMINANTS
│
├── 1. ADHESINS (Attachment factors)
├── 2. INVASINS (Invasion factors)
├── 3. TOXINS (Exo and Endotoxins)
├── 4. ANTIPHAGOCYTIC FACTORS
├── 5. IRON ACQUISITION MECHANISMS
├── 6. ENZYMES (Spreading factors)
├── 7. ANTIGENIC VARIATION
└── 8. SECRETION SYSTEMS

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1. ADHESINS / ATTACHMENT FACTORS (★★★):

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2. INVASINS / INVASION FACTORS:

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3. TOXINS (★★★★):

• Lipid A is the toxic moiety
• Activates macrophages → release TNF-α, IL-1, IL-6 → fever, shock
• Activates complement → inflammation
• Activates coagulation cascade → DIC
• Large doses → Septic shock, multi-organ failure

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4. ANTIPHAGOCYTIC FACTORS (★★★):

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5. SPREADING FACTORS / ENZYMES:

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6. IRON ACQUISITION:

• Iron is essential for bacterial growth
• Iron is sequestered by host (transferrin, lactoferrin, ferritin)
• Bacteria produce siderophores (e.g., enterobactin, aerobactin) that chelate iron from host proteins
• Example: E. coli produces aerobactin; M. tuberculosis produces mycobactin

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7. ANTIGENIC VARIATION:

• Bacteria change surface antigens to evade immune response
• Examples:
  • N. gonorrhoeae - Pilus phase variation
  • Borrelia recurrentis - relapsing fever due to antigenic variation
  • Influenza virus - antigenic drift and shift

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8. SECRETION SYSTEMS (Type I-VII):

• Protein complexes that transport virulence factors from bacterial cytoplasm to host cell
• Type III SS: Injects effector proteins directly into host cells (Salmonella, Shigella, Yersinia, EPEC)
• Type IV SS: Conjugation system; delivers DNA/proteins (H. pylori - CagA)
• Type VI SS: Kills competing bacteria and host cells

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Genetic Basis of Virulence:

1. Pathogenicity Islands (PAIs) - Large chromosomal segments (10-200 kb) encoding multiple virulence factors; have different GC content from rest of chromosome
2. Plasmids - Enterotoxin genes (E. coli ETEC), resistance genes
3. Bacteriophages - Cholera toxin gene (CTX phage), Diphtheria toxin (corynephage β), Botulinum toxin

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NEW PARADIGM - Damage Response Framework (Casadevall & Pirofski, 1999):

• Traditional definition focuses on organism; new paradigm focuses on HOST-PATHOGEN INTERACTION
• Infection = acquisition of microorganism by host
• Disease = DAMAGE caused by the interaction between microbe and host immune response
• Outcome of infection depends on virulence of organism AND immune status of host
• Even a non-virulent organism can cause disease in immunocompromised (e.g., MAI in AIDS)

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⭐ MUHS EXAM QUICK REVISION SUMMARY

Most Important Topics for MUHS (Mark as ★★★★):

1. Autoclave - Principle, working, complications, diagram
2. Exotoxin vs Endotoxin - 4 differences
3. Enrichment vs Enriched media - Differences + 2 examples each
4. Ethylene oxide - Mechanism, uses
5. Tyndallization - Principle, uses
6. Virulence determinants - Toxins, adhesins, antiphagocytic factors
7. Modes of transmission - Classification with examples

Temperature-Time Chart (Memorize!):

Autoclave:      121°C / 15 min / 15 lbs/in²
Hot Air Oven:   160°C / 1 hr
Pasteurization: 72°C / 15 sec (HTST) or 62°C / 30 min (LTLT)
Tyndallization: 100°C / 30 min × 3 days
Inspissation:   80-85°C / 30 min × 3 days

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