Nosocomial Infection: Introduction, Source, Control and Prevention

Nosocomial Infection: Introduction, Source, Control and Prevention


  • Nosocomial infections result from pathogens that develop within a hospital or other type of clinical care facility and are acquired by patients while they are in the hospital.
  • Besides harming patients, nosocomial infections can affect nurses, physicians, aides, visitors, salespeople, delivery personnel, custodians, and anyone who has contact with the hospital.
  • Most nosocomial infections come clinically apparent while patients are still hospitalized; however, disease onset can occur after patients have been discharged.
  • Infections that are incubating when patients are admitted to a hospital are not nosocomial; they are community acquired. However, because such infections can serve as a ready source or reservoir of pathogens for other patients or personnel, they are also considered in the total epidemiology of nosocomial infections.
  • The CDC estimates that about 10% of all hospital patients acquire some type of nosocomial infection.
  • Approximately 40 million people are admitted to hospitals annually, about 2 to 4 million people may develop an infection they did not have upon entering the hospital.
  • Nosocomial infections represent a significant proportion of all infectious diseases acquired by humans.
  • Nosocomial diseases are usually caused by bacteria, most of which are noninvasive and part of the normal microbiota; viruses, protozoa, and fungi are rarely involved.

Source of Nosocomial infections

  • The nosocomial pathogens that cause diseases are of two types endogenous or exogenous sources.
    • Endogenous sources are the patient’s own microbiota.
    • Exogenous sources are microbiota other than the patient’s.
  • Endogenous pathogens are either brought into the hospital by the patient or are acquired when the patient becomes colonized after admission.
  • In either case the pathogen colonizing the patient may subsequently cause a nosocomial disease (e.g., when the pathogen is transported to another part of the body or when the host’s resistance drops).
  • If it cannot be determined that the specific pathogen responsible for a nosocomial disease is exogenous or endogenous, then the term autogenous is used.
  • An autogenous infection is one that is caused by an agent derived from the microbiota of the patient, despite whether it became a part of the patient’s microbiota following his or her admission to the hospital.
  • There are many potential exogenous sources in a hospital.
  • Animate sources are the hospital staff, other patients, and visitors.
  • Some examples of inanimate exogenous sources are food, computer keyboards, urinary catheters, intravenous and respiratory therapy equipment, and water systems (e.g., softeners, dialysis units, and hydrotherapy equipment).
nosocomial infection
Relative frequency by body site.These data are from the National Nosocomial Infections Surveillance, which is conducted by the Centers for Disease Control and Prevention (CDC).

Control, Prevention, and Surveillance

  • In the United States nosocomial infections prolong hospital stays by 4 to 13 days, result in over 4.5 billion dollars a year in direct hospital charges, and lead to over 20,000 direct and 60,000 indirect deaths annually.
  • The enormity of this problem has led most hospitals to allocate substantial resources to the development of methods and programs for the sursurveillance, prevention, and control of nosocomial infections.
  • All personnel involved in the care of patients should be familiar with basic infection control measures such as isolation policies of the hospital; aseptic techniques; proper handling of equipment, supplies, food, and excreta; and surgical wound care and dressings.
  • To protect patients, hospital personnel must practice proper aseptic technique and handwashing procedures, and must wear gloves when contacting mucous membranes and secretions.
  • Patients should be monitored with respect to the frequency, distribution, symptomatology, and other characteristics common to nosocomial infections.
  • A dynamic control and surveillance program can be invaluable in preventing many nosocomial infections, patient discomfort, extended stays, and further expense.

Reference and Sources


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