2.1 Bacteriology, Disorders & Disease Control

2.1 Bacteriology, Disorders & Disease Control

Infection control is the most heavily weighted science block on the Texas Department of Licensing and Regulation (TDLR) cosmetology operator written exam (delivered by PSI, roughly 100 scored questions, 70% to pass). The state tests it hard because preventing disease transmission is the core of public protection.

Classifying Microorganisms

Bacteria are one-celled microorganisms. The two functional groups you must distinguish are nonpathogenic (harmless or beneficial — about 70% of all bacteria, including the flora that digest food) and pathogenic (disease-producing). Pathogenic bacteria are classified by shape:

Cocci subdivide by grouping: staphylococci form grape-like clusters and cause boils and pustules; streptococci form chains and cause blood poisoning; diplococci grow in pairs.

Movement, Growth, and Spores

Bacilli and spirilla are motile — they move using whip-like flagella (or cilia). Cocci are generally nonmotile. Bacteria reproduce by mitosis (simple cell division, called binary fission): under favorable warm, dark, damp, and dirty conditions one cell splits into two roughly every 20–60 minutes. When conditions turn unfavorable, certain bacilli (anthrax, tetanus) form spores with tough outer shells that resist heat, light, and disinfectants — which is why ordinary salon disinfection cannot guarantee sterilization.

Viruses, Fungi, and Parasites

• Virus — a submicroscopic particle that replicates only inside a living host cell. Examples relevant to the salon: hepatitis B (HBV), hepatitis C (HCV), and human immunodeficiency virus (HIV). HBV is the salon's greatest bloodborne concern because it survives on surfaces and is far more contagious than HIV.
• Fungi — plant-like microbes that include molds, mildews, and yeasts. Tinea (ringworm) is a contagious fungal infection; tinea pedis is athlete's foot; tinea capitis is ringworm of the scalp.
• Parasites — organisms that live on or in a host. Pediculosis capitis is infestation by head lice; scabies is caused by the itch mite burrowing under the skin.

How Infection Spreads and the Body's Defenses

A contagious (communicable) disease spreads by direct contact, by contaminated implements, in airborne droplets, or via open wounds. Contamination is the presence of pathogens; infection occurs when the body cannot fight them off. Defenses include unbroken skin, body secretions (perspiration, digestive juices), white blood cells that destroy bacteria, and immunity — the body's ability to resist infection. Natural immunity is inherited; acquired immunity develops from overcoming a disease or from vaccination (e.g., the HBV vaccine).

Disorders the Operator Must Recognize and Refer

Texas law requires an operator to refuse service when a client shows signs of an infectious or inflamed condition and to refer the client to a physician — never diagnose or treat.

Distinguish contagious conditions (refer) from cosmetic ones you may treat: dandruff (pityriasis), simple dry scalp, and canities (gray hair) are not infectious. A common exam trap pairs a treatable cosmetic condition with an infectious one and asks which client you may serve.

The Three Levels of Decontamination

Texas tests the difference between three levels of removing contaminants, and confusing them is a frequent exam trap:

1. Sanitation (sanitizing) — the lowest level; simply reduces germs on a surface (washing hands, cleaning a station with soap and water). It does not kill pathogens.
2. Disinfection — the salon standard for nonporous tools; kills most bacteria (but not bacterial spores) on hard, nonporous implements such as metal shears, combs, and clippers.
3. Sterilization — destroys all microbial life including spores, using an autoclave; required in medical settings, not for routine salon tools.

Porous, single-use items (orangewood sticks, emery boards, neck strips, buffer blocks) are never disinfected for reuse — they are discarded after one client because their absorbent surface cannot be reliably disinfected.

TDLR Disinfection Standard

To break the chain of infection, TDLR requires implements to be cleaned of all visible debris first, then immersed in or sprayed with an EPA-registered disinfectant labeled bactericidal, fungicidal, and virucidal (or a 10% bleach solution), used per the manufacturer's instructions. Wet disinfectant solutions must be mixed fresh daily (or sooner if cloudy or soiled), and disinfected tools must be stored in a clean, covered, dry container. Blood or body fluids require immediate cleanup with an EPA-registered, tuberculocidal-level disinfectant.

Following Standard Precautions — treating all blood and body fluids as if infectious — protects the operator from HBV and HCV exposure.

Chain of Infection and Exam Strategy

Infection requires six links: a pathogen, a reservoir (a person or tool harboring it), a portal of exit, a mode of transmission, a portal of entry, and a susceptible host. Disinfection breaks the chain at the reservoir and transmission links. When the exam describes a scenario, identify the link being broken: discarding a porous file removes the reservoir; wearing gloves blocks the portal of entry. Remember the hierarchy of caution — when in doubt about whether a condition is contagious, refuse, refer, and disinfect, because protecting public health always outranks completing a service.