Safety, Infection Control & Medical Asepsis

Infectious Agents and the Chain of Infection

Infection control is a high-yield area because it appears throughout the Clinical Competency section and underlies every patient encounter. Begin with the four classes of pathogens and the six-link chain that spreads them.

Classes of Infectious Agents

The Six-Link Chain of Infection

1. Infectious agent — the pathogen itself.
2. Reservoir — where it lives (humans, animals, equipment, water).
3. Portal of exit — how it leaves (respiratory droplets, blood, feces).
4. Mode of transmission — direct (person-to-person contact) or indirect (fomites, droplets, vectors, airborne).
5. Portal of entry — how it enters a new host (broken skin, mucous membranes, inhalation).
6. Susceptible host — a person at risk (immunocompromised, very young, elderly).

Breaking any single link stops the infection. Hand hygiene breaks the transmission link; sterilizing instruments removes the reservoir; immunization reduces host susceptibility. The body's natural barriers — intact skin, mucous membranes, stomach acid, normal flora, and the inflammatory/immune response — defend against entry.

Standard Precautions, PPE & OSHA

Standard Precautions

Standard Precautions assume the blood and body fluids of every patient may be infectious. They apply to all patients regardless of diagnosis and include hand hygiene, appropriate PPE, safe injection practices, respiratory hygiene/cough etiquette, and safe handling of contaminated equipment and surfaces.

Transmission-based precautions add to Standard Precautions for known pathogens:

Donning and Doffing PPE

• Don (put on) order: gown -> mask/respirator -> goggles/face shield -> gloves.
• Doff (remove) order: gloves -> goggles/face shield -> gown -> mask/respirator, performing hand hygiene after removal. Gloves are removed first because they are the most contaminated.

Hand Hygiene

Hand hygiene is the single most effective infection-control measure. Use alcohol-based hand rub for routine decontamination of hands that are not visibly soiled. Use soap and water when hands are visibly soiled, after using the restroom, and after caring for a patient with C. difficile or norovirus (alcohol does not kill these spores).

OSHA Bloodborne Pathogens Standard

OSHA requires employers to: maintain a written Exposure Control Plan, provide PPE at no cost, offer the hepatitis B vaccine free to at-risk employees, use engineering controls (sharps containers, self-sheathing needles), follow work-practice controls, and provide a documented post-exposure protocol with an accessible eyewash station. After a needlestick, wash the site, report immediately, and follow the post-exposure evaluation.

Asepsis, Disinfection & Regulated Waste

Medical vs. Surgical Asepsis

Levels of Decontamination

• Sanitization — physically cleans and lowers microbe counts (e.g., washing instruments before sterilizing).
• Disinfection — destroys most pathogens on surfaces/inanimate objects (chemical disinfectants).
• Sterilization — destroys ALL microorganisms and spores; the autoclave (steam under pressure, typically 250-273 deg F / 15-30 psi) is the standard. Sterilization indicators and quality-control checks confirm a successful cycle.

Biohazard and Regulated Waste Disposal

Do not overfill sharps containers (replace at the fill line). Use a spill kit with PPE and an absorbent for blood/body-fluid spills, then disinfect the area.

Safety Resources: SDS and GHS

The Safety Data Sheet (SDS) provides chemical hazard, handling, storage, and first-aid information and must be readily accessible to staff. The Globally Harmonized System (GHS) standardizes hazard pictograms and labels so chemical risks are recognized at a glance. Recognizing safety signs, symbols, and labels is explicitly tested.

CLIA Context, Cleaning Hierarchy & High-Yield Distinctions

Infection control overlaps with the laboratory and the front office, and the exam expects you to connect these areas.

Spaulding Classification of Instruments

The level of decontamination depends on how an item contacts the patient:

Cleaning Sequence

Always sanitize first, then disinfect or sterilize. Organic material such as blood and tissue must be removed before sterilization, because debris shields microorganisms from steam and chemicals and causes a failed cycle.

Autoclave Quality Control

• Chemical indicators (tape/strips) confirm the item was exposed to the process but not that sterility was achieved.
• Biological indicators (spore tests) are the only way to verify true sterilization and are run on a routine schedule.
• Wrap, label, and date packs; a properly stored sterile pack has an expiration based on the wrapping and storage conditions.

High-Yield Distinctions

• Asepsis vs. antisepsis vs. disinfection: asepsis is the overall absence of pathogens; antiseptics are applied to living tissue (skin prep); disinfectants are applied to inanimate surfaces and are too harsh for skin.
• Sanitize -> disinfect -> sterilize moves from fewest to most microbes destroyed.
• Surgical asepsis is required any time the skin is broken or a sterile body cavity is entered; routine injections use medical asepsis with antiseptic skin prep.

Keeping these definitions straight prevents the most common errors on infection-control items and links directly to the laboratory CLIA and specimen-handling questions elsewhere on the exam.