1. Chain of infection
a. Reservoir
i. A source of infection, a place where pathogens survive and
multiply. Most pathogens flourish in a warm, dark, environment like
the human body.
ii. Living and nonliving fomite reservoirs, vectors like animals/ insects
iii. Spores can live without water. 95 degrees ideal temp for pathogens
iv. Most bacteria, protozoa, fungi are aerobic.
v. Most prefer pH of 5-8
b. Portal of exit
i. Most frequently through body fluids, body tries to expel pathogens
through coughing, sneezing, diarrhea, vomit
ii. Non-intact skin, wounds, bites, abrasions, blood and pus in wounds
help transport pathogens.
iii. In HAIs- puncture sites, drainage tubes, feeding tubes and IV lines
are portals of exit for pathogens
c. Mode of transmission
i. Contact is the most frequent mode of transmission
1. Direct contact: physical, sexual, contact with fluids,
scratching or biting
2. Indirect contact: contact with fomite nonliving contaminated
reservoir. Shoes, eyeglasses, stethoscopes are fomites.
3. Droplet transmission: pathogen expelled through exhalation,
coughing, sneezing, talking, suctioning, oral care. Is inhaled
or enters the eye of susceptible host. Travel less than 3 feet.
Larger than 5 microns. PIMP
4. Airborne transmission: MTV. Smaller than 5 microns, travels
more than 3 feet.
5. Vector: ticks, mosquitos.
d. Portal of Entry
1. Normal body openings: conjunctiva of the eye, nares, mouth,
urethra, vagina, anus. Wounds, abrasions.
2. Vectors can create portals of entry via bites/stings.
e. Susceptible Host
1. A person at risk for infection because of inadequate
defenses against the invading pathogen.
a. Age, compromised immune system, chronic illness,
immune deficiency
2. Stages of a Typical Infectious Process
a. Incubation
i. Infection begins in this stage between successful invasion of the
, pathogen into the body and the first appearance of symptoms.
Person can infect others, incubation period varies.
b. Prodrome
i. Characterized by the first appearance of vague symptoms at the
onset of illness. Not all infections have a prodromal stage.
c. Illness
i. Patient becomes ill when the first signs and symptoms appear. Can
end in death if immune system is ineffective
d. Decline
i. When the patients immune defenses, along with medical therapies,
successfully reduce the number or pathogenic microbes
e. Convalescence
i. Healing begins as the remaining number of microorganisms
approaches zero.
3. Precautions to prevent transmission of infection
a. Use standard precautions for all patients
b. Practice impeccable hand hygiene
c. Ensure patient areas are cleaned well and often; disinfect high-touch
surfaces
d. Use masks and eye protection when splashes are possible
e. Use private rooms, isolation precautions when necessary
f. Dedicate non-critical equipment to use for individuals with MDRO infection
4. Factors That Increase the Risk For Infection
Age, Breaks in Skin, Illness/Injury, Tobacco/substance use, multiple sexual
partners, environmental factors, chronic disease/poor circulation, medications,
invasive procedures.
a. Developmental stage
i. The young are vulnerable because their immune systems are
immature, pathogen exposure is limited.
ii. The old are susceptible because immune response declines with
aging. Skin becomes less elastic and more prone to breakdown.
Elderly may be less active and can have inadequate nutrition.
b. Breaks in the first line of defense
i. Break in the skin via surgical procedure, breakdown or insect bite,
insertion of an IV or catheter device, all create portals of entry
c. Illness or Injury
i. Recuperation from infection or injury limits the physical resources
available to combat a new pathogen.
d. Tobacco Use
i. Smoking interferes with the ability to move the chest, cough,
sneeze or have full air exchange.