Also known as Hospital associated Infection, hospital infection or Nosocomial infection.It is defined as infection developed in patients after admission to the hospital, which was neither present  in the incubation period nor at the time of hospitalisation.Such infections may become evident during their stay in the hospital or, sometimes, after their discharge.

Factors influencing Infection:

  1. Susceptible patients
  2. Hospital environment
  3. Diagnostic and therapeutic procedures
  4. Drug Resistance
  5. Transfusion
  6. Advances in medical progress

Sources Of Infections


Hospital infection is mostly exogenous from another patient or member of the staff or from the environment in the hospital.


Patients own flora may invade the patient’s tissue during some surgical operation.

Mode of Transmission


Contact by hands and clothing’s of attendants.

Certain instruments (endoscope, bronchoscope, cystoscope) if not properly disinfected, may transmit pathogenic organisms.


Inhalation of infected droplets, aerosols and dust from beddings or floors can cause airborne infections.


Hospital food may contain antibiotics – resistant bacteria (E.coli, Klebsiella spp., pseudomonas aeruginosa) which may colonise the intestine and later cause infection in susceptible patients.


Infection may be transmitted by:

Blood transfusion, contaminated blood products and contaminated infusion fluids.

Common Health Associated Infections

Five common types of HAI are:

  1. Urinary tract infections (UTI): This is usually associated with catheterisation or instrumentation of urethra, bladder or kidneys. UTI associated with catheterisation is named as 

Catheter associated UTI.The causative organisms are E.coli, Klebsiella,Proteus, Pseudomonas, CONS, Enterococci and Candida albicans.

  1. Surgical wound infections (SWI): Post-operative wound infections are also called surgical wound infections. The causative organisms are Pseudomonas aeruginosa, S.aureus, E.coli, Proteus, Enterococci and CONS

3. Respiratory Infections:Aspiration in unconscious patients and pulmonary ventilation may lead to nosocomial pneumonia. Causative organisms are S.aureus, Klebsiella, enterobacter, Proteus, E.coli, Pseudomonas aeruginosa, Acinetobacter and respiratory viruses.

4. Gastrointestinal Infections: Food poisoning and neonatal septicaemia in hospitals have been reported. Causative organisms are Salmonella, shigella and viruses.

5. Blood stream infection: Causative organisms are S.aureus, CONS, Enterococcus, E.coli, Klebsiellapneumoniae and Serratia spp.

Diagnosis and Control

  • Diagnosis is by routine bacteriological methods. This requires  samples from possible sources of infection such as hospital personnel, inanimate objects, water, air or food.
  • Control of hospital infection done by treating the cause.


  • Antibiotic therapy to the carrier staff or source patient.
  • Proper sterilisation and disinfection of the inanimate objects.
  • Disinfection of excreta and infected material.
  • Regular washing of hands, disinfection of equipments and change of working clothes.
  • The use of sterile dressings, surgical gloves, faces masks and I/V fluids.
  • Preoperative disinfection of the patient’s skin.
  • Proper investigation of health associated infection and the treatment of such cases.

ESKAPE Pathogens

The ESKAPE pathogens are:

E- Enterococcus

S- Staphylococcus aureus

K-  Klebsiellapneumoniae

A- Acinetobacter

P- Psudomonasaeruginosa

E- Enterobacter spp.

Are the leading causes of nosocomial infection throughout the world.