Infection Prevention and Control Principles
This domain tests whether you can apply the chain of infection, standard and transmission-based precautions, hand hygiene, and the Spaulding classification to real ambulatory and reprocessing decisions, rather than recite definitions. CAII and CMII items usually present a scenario and ask which precaution, product, or sequence is correct.
Core rules
- The six links are infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host. Any single broken link interrupts transmission.
- Standard precautions apply to every patient regardless of diagnosis: hand hygiene, risk-based gloves/gown/mask/eye protection, safe sharps handling, and environmental cleaning.
- Transmission-based precautions add contact (MRSA, C. difficile, scabies), droplet (influenza, pertussis), or airborne (tuberculosis, measles, varicella) measures; airborne requires an N95 respirator and, where available, a negative-pressure room.
- Spaulding classification drives reprocessing: critical items contact sterile tissue and must be sterilized; semicritical items contact mucous membranes and need high-level disinfection; noncritical items contact intact skin and need low-level disinfection.
- Use alcohol-based hand rub for routine decontamination, but soap and water when hands are visibly soiled and after known or suspected C. difficile or norovirus, because alcohol does not reliably kill spores.
Worked example
A patient with suspected C. difficile diarrhea shares a room, and a coworker asks for alcohol rub before leaving. Reasoning: C. difficile is spread by spores, which survive alcohol. The correct action is contact precautions, gown and gloves, dedicated equipment, soap-and-water handwashing with friction, and a sporicidal (chlorine-based) disinfectant per facility policy.
Traps that cost marks
Gloves never replace hand hygiene; remove PPE before leaving the room, then clean hands. Selecting airborne precautions for droplet diseases (or the reverse) is a frequent error. Do not assume a diagnosis is needed before applying standard precautions - they are universal.