Asepsis and the Chain of Infection

The transmission of infection depends on six elements which link together like a chain.  If any link is broken then the chain is broken and infection cannot be transmitted.  The elements are infectious agent, a reservoir for its growth, a portal of exit into the host, and a susceptible host.  The practice of medical asepsis refers to methods of breaking the chain of infection.

Asepsis is a term referring to the absence of pathogens.  Medical asepsis consists of techniques used to reduce the number of microorganisms and help reduce or prevent their spread.  It is also known as clean technique.

The elimination of microorganisms from an area is known as surgical asepsis or sterile technique.  The techniques used in maintaining surgical asepsis are more rigid than those performed under medical asepsis.

Asepsis is best learned by learning principles that can be applied to multiple situations.  The following table states principles for each of the links in the chain of infection and sites examples of practice.

Elements of Infection Chain

Medical Asepsis Principles and Practice


Infectious agent (pathogen, etiologic agent):  includes bacteria, viruses, and fungi that normally inhabit skin, mucous membranes.


Ability of organism to cause disease is related to agent characteristics:  capable of reproducing; requires food and proper temperature; requires presence or absence of oxygen; able to resist chemical or physical agents; may or may not produce toxins.


  • Clean contaminated objects (reduces the number of organisms).
  • Perform disinfection and sterilization (kills or inactivities organisms).
  • Use antiseptics to inhibit growth.
  • Use antiinfective agents (antibiotics or bacteriostatics)

Reservoir:  habitat of organism (where they grow and reproduce)


Pathogenic and nonpathogenic organisms constantly exist in the internal and external environments.

Dry, cool, well ventilated areas are less conductive to microbial growth than moist, warm, unventilated areas.  Ability of organism  to cause disease is related to environmental support.  Any factor which increases environmental support decreases the likelihood of infection.  Contamination in clean technique occurs if dirty objects come in contact with clean objects.  Cleaning of any object proceeds from clean to dirty.


  • Eliminate sources of body fluids and drainage.
  • Bathe with soap and water.
  • Change soiled dressings.
  • Remove standing water on bedside tables.
  • Cover bottles of used solutions.
  • Maintain patency of surgical wound drains.
  • Empty and rinse suction bottles.
  • Empty drainage bags every shift.
  • Place syringes and uncapped needles in moisture-resistant, puncture-proof containers.
  • Limit contact with persons with infection or exposed to infection.

Portal of Exit:  the primary route of escape for the organism


Isolation techniques set up a barrier to the transfer of microorganisms.

Maintenance of clean technique requires that only clean or sterile objects come in contact with clean objects.


  • Respiratory - avoid talking, sneezing or coughing directly over wound or sterile field.  Cover nose and mouth when sneezing or coughing.  Wear mask if suffering respiratory tract infection.
  • Blood and wound drainage - wear gloves to handle blood and body fluids.  Dispose of soiled dressings in container marked for contaminated wastes.
  • Urinary and gastrointestinal - wear gloves to handle urine, feces, and emesis particularly if it is contaminated with blood.

Transmission:  The method by which organisms are spread are:

Direct contact (kissing, intercourse)

Indirect droplet contact via moist surfaces (water glasses, food utensils, hands, clothes, air movement)

Via vectors (ticks, bats, mosquitos)


Dispose of linen in linen bag.

Isolation techniques set up a barrier to the transfer of microorganisms.  Maintenance of clean technique requires that only clean or sterile objects come in contact with clean objects.


  • Reduce microorganisms spread.
  • Wash hands.
  • Use personal set of care items for each client.
  • Avoid shaking bed linens or clothes.
  • Discard any item that touches the floor.

Portal of entry:  frequently the same as portal of exit


Body cavities have naturally occurring resident flora.


  • Skin and mucous membranes - Maintain skin and mucous membrane integrity.  Use proper hygiene measures.
  • Clean wound sites thoroughly.  Dispose of used needles in proper receptacles.
  • Urinary - Keep all drainage systems closed and intact.
  • Discard facial tissues, wound dressings, and other body excreta without touching.



Inflammation is a naturally occurring defense of the invasion by any type of foreign agents.  An intact immune system is necessary for successful defense against invading microorganisms.  The body's secretions of tears, digestive juices, and mucous have bacteriostatic properties which protect against invasion.  Healing is related to the amount of tissue damage and the level of wellness of the individual.  Healing cannot occur in the presence of infection.  Infants, children, and older adults are more susceptible to skin damage and infection than are other age groups.


  • Provide adequate nutrition.
  • Ensure adequate rest.
  • Promote body defenses against infection.
  • Provide immunizations.