Chapter 4 Infection Prevention

The Disease Transmission Cycle

Understanding Mode of Transmission 

The infectious agent is the disease-producing microorganism

The reservoir of pathogenic microorganisms may be a human source (i.e., patients, HCWs, or visitors), animals, plants, the soil, air or water.

The mode of escape, (how the pathogenic microorganism leaves the reservoir) could be via coughing, sneezing, contamination of hands and surfaces with blood and body fluids.

Mode of transmission is how the agent travels from person to person, this usually occurs via HCWs’ hands, contaminated equipment, instruments, devices, and the environment (including air and water).

Portal of entry, is where pathogenic microorganism can enter to infect susceptible host. Common places of entry include the mucus membrane, blood, surgical site, and urinary tract.

Susceptible hosts are patients, HCWs, and visitors who may become infected by the infecting microorganisms.

Resistance to infection will depend on the individual’s immune system, with some individuals becoming infected but remaining asymptomatic carriers while others become infected and develop a clinical disease.

Factors such as age, underlying diseases, and use of certain treatments (e.g., antimicrobials, corticosteroids, chemotherapy, and other agents that decrease immunity) play a role in the infection process. 

Breaking the Chain

Components of the chain of infection and where it's possible microbiologists and health care workers/professionals can break the chain

Methods Used to Disinfect and Sterilize

There are several methods used to disinfect and sterilize medical equipment and facilities. Review each of the following methods in our textbook (pg 98-104)

Heat

Pasteurization

Boiling water Steam and pressure

Various liquids and compounds

Gas sterilization

Basic Definitions

Denatured means structurally altered. It typically results in death of a substance or organism 

Sanitation is a general term for any process that reduces the total bacterial contamination to a level in which an object can be safely handled

Decontamination is the process used to remove contaminants by chemical or physical means

Disinfection is the process that eliminates vegatative, pathogenic microorganisms from an inanimate object and there are four levels of disinfection 

Low-level disinfectants are germicidal that can kill some but not all vegetative bacteria and fungi and denature some viruses

Intermediate-level disinfectants are germicidal agents that can kill all gram-negative bacterial and fungi but have variable success against spores and their ability to denature certain viruses

High-level disinfectants are capable of killing all microorganisms except their spores

Sterilization is the complete destruction or inactivation of all forms of microorganisms. Sterilization is a technique in which their is complete destruction of microorganisms on inanimate objects using heat, water, chemicals or gases (as referred to above).

Different Levels of Susceptibility on Various Microorganisms