This term uses a metaphor to create a visual interpretation; each link depends on the last and the next, in order to continue. Break one link and there is no longer a connection. An example might be:
- The 1st link in the chain is the causative agent or pathogen, let’s use MRSA
- The 2nd link is the reservoir or the house the pathogen lives in. In this case it’s living in the nares (nose) of a nurse but not causing her any
clinical signs of infection. She is not even aware she has MRSA organisms in her nasal passages.
- The 3rd link is the portal of exit (the nurse rubs her nose, now the pathogen is on her hands).
- The 4th link is the mode of transmission or the route the organisms use to travel to their newest destination; in this case, the nurse’s unwashed hands.
- The 5th link is the portal of entry or the skin of the potential host, her patient.
- The 6th link is the susceptible host, the patient; susceptible is the keyword. If the patient has an altered immune system, and chronically ill people do, the organism stands a very good chance of gaining entrance and setting up shop at
the first opportunity.
So let’s see what happens. The nurse did not take the time to wash her hands before visiting her patient and so she transmits the MRSA to her patient’s skin while taking her blood pressure.
The patient is a susceptible host because her immune status is impaired by her chronic medical conditions and diabetes. The patient’s arm itches, she scratches it and causes a small break in the integrity of her skin; the MRSA she picked up from the nurse gains entrance (portal of entry) and the patient develops an MRSA wound infection.
Looking back we can see any one of the links in the chain of infection could easily have been broken, beginning with the nurse always washing her hands or using an alcohol sanitizer before and after visiting each patient.
The concept of breaking the chain of infection is not limited to long-term care; it can and should be used to prevent transmission of micro-organisms in all healthcare facilities and in the community as well. If we could see the multitude of organisms that are living on our hands and in our immediate environment, we would probably never stop washing our hands.