Infection Prevention and Control: The Chain of Infection and Standard Precautions
The organizing idea
Every infection prevention question ultimately reduces to the chain of infection: a pathogen needs a reservoir, a portal of exit, a mode of transmission, a portal of entry, and a susceptible host. Break any link and transmission stops. Candidates should be able to name which link a given intervention targets - hand hygiene interrupts transmission from contaminated hands to mucous membranes; environmental cleaning reduces the reservoir; PPE blocks portals of entry and exit; vaccination and skin integrity protect the host.
Standard vs. transmission-based precautions
Standard precautions apply to all patients regardless of diagnosis, because colonization and asymptomatic carriage are common. They include hand hygiene, gloves when contact with blood, body fluids, secretions, excretions, non-intact skin, or mucous membranes is anticipated, gown when splashing or soiling is likely, and facial protection when splash or spray is anticipated. Transmission-based precautions (contact, droplet, airborne) are added on top of standard precautions, never instead of them. A frequent trap is a question implying that a patient on contact precautions does not also need standard precautions.
Hand hygiene specifics
Alcohol-based hand rub is preferred for routine decontamination when hands are not visibly soiled; soap and water are required when hands are visibly soiled and for spore-forming organisms such as C. difficile and norovirus, because alcohol does not reliably kill spores. Gloves do not replace hand hygiene - perform it before donning and after doffing.
Traps to watch
Questions often test sequence (doffing order, when to clean), the difference between a precaution that is added versus substituted, and the distinction between colonization and infection. Read the stem for whether the patient is symptomatic.
Rule of thumb
"Gloves are a barrier, not a substitute." If a stem describes a task with anticipated contact with body fluids, the answer almost always includes gloves plus hand hygiene at the appropriate moments.
Worked example
A patient has an uncontained draining wound. Anticipated contact with the drainage means contact precautions are added, gloves and gown are used for room entry, and hand hygiene is performed before donning and after doffing - while standard precautions for all other care continue.