Hospital Acquired Infection

Nosocomial infection


Nosocomial infection Definition – 

Hospital-acquired infection is also known as nosocomial infection and healthcare-associated infection.

  • According to Dr. William James – Infections are most often transmitted from patient to patient on the hands of healthcare workers.
  • According to WHO – An infection is acquired in a Health Care setting other than the primary reason for admission.
  • The nosocomial infection is developed at least 48 hrs after the admission and discharge.
  • Infection is the transmission of pathogens between the staff and patients and among patients.


Source of nosocomial infection

  1. Exogenous
  2. Endogenous


  1. Exogenous nosocomial infection – 

A hospital-acquired infection is mostly an exogenous form, that is transferred through another patient, hospital staff or hospital environment.

eg:- hospital equipment and devices.

  • Hospital environment – air, water, food etc.
  • Hospital patient secretion, excretion, blood product and body fluids.


  1. Endogenous nosocomial infection – 

The infection occurs through normal human flora.

  • Infection is caused by the organism that is present as a part of the normal flora of the patient.



  • All microorganisms can cause a nosocomial infection that is – viruses, bacteria, fungi and parasites.
  • Blood borne viral infections are – HIV, HCV, and HBV.
  • Other viral infections are – Rubella, SARS, and varicella.
  • Gram-negative bacteria are
  • Pseudomonas aeruginosa
  • E – Coli
  • Neisseria gonorrhoea etc.
  • Gram-positive bacteria are
  • Mycobacterium tuberculosis
  • Staphylococcus aureus
  • Staphylococcus epidermidis
  • Fungal infections are – candida albicans
  • Aspergillus etc.


Mode of transmission

  1. Contact – It is the most common route of transmission of nosocomial pathogens.
  • Hands and clothes – The infection is spread through contact with the hand and clothes of hospital staff.
  • It is an adequate scope of microorganism transmission from one person to another person.
  • Hospital equipment – Some hospital equipment such as bronchoscopes, endoscopes, cystoscopes, etc. are infected, which is responsible for to spread of the infection.


  1. Airborn

  • Droplet – Some infection particles are transmitted through inhalation routes.
  • Aerosols – The infection is transferred through nebulizers, humidifier and air conditioner etc.
  • Dust – Infection spread from bed making, floors, from wound during dressing etc.


  1. Parenteral route – The infection is spread through contaminated fluid infusion, blood transfusion, provide contaminate blood products and tissue donation etc.
  • For example – hepatitis and HIV virus also transfer through parenteral route.


  1. Oral route – Infection is spread through ingestion of contaminated food and water.


Types of Nosocomial infection

What are the 6 most common hospital-acquired infections?
  1. Respiratory infection 

 This type of nosocomial infection is spread through pulmonary ventilation and aspiration in unconscious patients.


  1. Urinary tract infection – 

These types of infections occur due to contaminated proceeding techniques of catheterization or unhygienic care of dressings.

  • The infection is prevented by the use of an aseptic technique during catheterization.


  1. GI infections 

 Infection occurs due to ingestion of contaminated food and fluid.


  1. Surgical infection – 

In the elder patient, post-operative infection is high. The infection occurs due to a lack of asepsis technique during surgery and during the dressing of wounds.


  1. Burn – 

In case of burn, staphylococcus aureus, streptococcus pyogenes, and pseudomonas aeruginosa are essential to cause hospital-acquired infection.


  1. Bacteraemia – 

Infection is spread through the infected intravenous cannula etc.


Prevention of Nosocomial infection

  • Proper hand washing is the most important vehicle to prevent the hospital from acquiring infection.
  • Use the alcohol hand rub.
  • Administer the antibiotics to the carrier staff or patient to destroy the pathogenic agents.
  • Isolated the infectious patient.
  • Use proper sterilization and disinfection techniques.
  • During the procedure, always use sterile equipment and dressing material.
  • All surgical and medical procedures are done under aseptic techniques.
  • Maintain proper personal hygiene.
  • Proper disposal of the hospital waste material.
  • Prevent overcrowding in the hospital and always use a face mask.
  • Maintain a well-ventilated hospital environment.
  • Staff use PPE kits during surgical procedures.
  • Standards to be maintained in the hospital.
  • Use proper investigation procedures.
  • Careful handling, cleaning and discarding the excreational waste.
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