The Chain of Infection
Disease transmission follows a predictable sequence called the chain of infection. Six links must all be present for an infection to spread. Breaking any one link stops transmission.
- Pathogen: The infectious agent (bacteria, virus, fungus, or parasite).
- Reservoir: Where the pathogen lives and multiplies (human, animal, environment).
- Portal of exit: How the pathogen leaves the reservoir (respiratory secretions, blood, skin flakes).
- Mode of transmission: How it moves from host to host.
- Portal of entry: How it enters a new host (cut, mucous membrane, inhalation).
- Susceptible host: A person who can become infected.
Modes of Transmission
- Direct contact: Touching an infected person or their fluids directly.
- Indirect contact: Touching a contaminated surface or implement.
- Droplet: Respiratory droplets from coughing or sneezing travel short distances.
- Airborne: Tiny particles remain suspended and travel farther (tuberculosis).
- Vector-borne: Transmitted by an intermediate organism (mosquitoes, ticks; not common in salon settings).
Types of Bacteria
Bacteria are classified by their shape. The shape is a key identifier on written exams.
| Shape | Name | Examples |
|---|---|---|
| Spherical (round) | Cocci | Staphylococci (clusters), Streptococci (chains), Diplococci (pairs) |
| Rod-shaped | Bacilli | Tuberculosis (Mycobacterium tuberculosis) |
| Spiral | Spirilla | Syphilis (Treponema pallidum) |
FATTOM: What Bacteria Need to Grow
Bacteria thrive under specific conditions. FATTOM is the acronym used to remember them:
- F - Food (proteins, carbohydrates)
- A - Acidity (neutral to slightly acidic pH, 4.6 to 7.5)
- T - Time (bacteria can double every 20 minutes)
- T - Temperature (40 to 140 degrees F is the "danger zone")
- O - Oxygen (most bacteria are aerobic; some are anaerobic)
- M - Moisture (bacteria need water to grow)
Viruses and Fungi
Viruses are not alive in the traditional sense. They require a living host cell to replicate. They are smaller than bacteria and not affected by antibiotics. Common salon-relevant viruses: hepatitis B, hepatitis C, HIV, herpes simplex (oral cold sores, can spread via shared implements).
Fungi include molds, yeasts, and mildew. Common fungal infections: tinea capitis (scalp ringworm), tinea pedis (athlete's foot), tinea unguium (nail fungus, also called onychomycosis).