Definitions - Infection Prevention and Control

ARO (Antibiotic Resistant Organism)

A microorganism that has developed resistance to the action of several antimicrobial agents and that is of special clinical or epidemiologic significance.


The absence of pathogenic (disease-producing) microorganisms. Can be further divided into:

  • Aseptic technique - practices designed to render and maintain objects and areas maximally free from microorganisms. Also called sterile technique.
  • Clean technique - refers to practices that reduce the numbers of microorganisms and minimizes the risk of transmission from personnel or environment to the patient.


Popularly called “germs”. Bacteria are very small microorganisms visible only through a microscope. There are many varieties, only some of which cause disease.


An individual who is found to be persistently colonized (culture-positive) for a particular organism, at one or more body sites, but may have no signs or symptoms of infection.


Presence of microorganisms in or on a host with growth and multiplication but without tissue invasion or cellular injury.


The presence of microorganisms on inanimate objects (e.g. clothing, surgical instruments) or microorganisms transported transiently on body surfaces such as hands, or in substances (e.g. water, food, milk).


To remove disease-causing microorganisms and leave an item safe for further handling.


The inactivation of disease producing microorganisms on non-living items.


(Normal) bacteria normally residing in a given area of the body.


An organism that is filamentous or thread like in structure ie. yeast, mushrooms.


The entry and multiplication of an infectious agent in the tissues of the host

  • (a) Inapparent (asymptomatic, subclinical) infection: an infectious process running a course similar to that of clinical disease but below the threshold of clinical symptoms
  • (b) Apparent (symptomatic, clinical) infection: one resulting in clinical signs and symptoms (disease).


An organism that can be seen only with the aid of a microscope and that typically consists of only a single cell. Microorganisms include bacteria, protozoans, and certain algae and fungi. Also called germs.

Multi Resistant Organism

Bacteria that have developed or acquired resistance to numerous antibiotics.

Nosocomial Infection

An infection occurring in a hospitalized patient, 72 hours or more after admission (no evidence that infection was present or incubating at the time of admission). Also includes infections directly related to a previous hospitalization.

PPE (Personal Protective Equipment)

Equipment worn as part of routine practices to protect from exposures to workplace hazards including blood and body fluids. Gloves, aprons, gowns, face shields and masks.


An organism that in most cases cannot be seen through a standard lab microscope. It is a parasite dependent on nutrients inside the host cells for its metabolic and reproductive needs.