Nosocomial Infections: Definition,Types and Prevention
Nosocomial Infections: Definition,Types and Prevention

Nosocomial Infections: Definition,Types and Prevention

Nosocomial infections – Definition, History, Epidemiology, Sources, Transmission, Type, Diagnosis, Control


The term “Nosocomial” comes from Greek word:

  • “Nosus” meaning “Disease”
  • “Komeion” meaning “to take care of”

Nosocomial infections are those infections acquire in hospital and are specifically not present to the patient’s being admitted to the hospital.

It is also known as Hospital Acquired Infections (HAIs) or Hospital Associated Infections.

HAIs affects patients and also staff members, visitors, food suppliers etc. It is very common in developed countries (Germany, Norway, Australia, and Sweden etc.) as well as developing countries India.

Epidemiology or Distribution of HAIs:

  • A study by the International nosocomial infection control consortium found that the rates of HAIs in India is very high. For example, in 2016, 290 children died in a tertiary referral hospital in Gorakhpur, Uttar Pradesh.
  • The patients in ICU, burn units, undergoing organ transplantation and neonates are very much susceptible to such infections.
  • According to Extended Prevalence of Infection in Intensive Care (EPIC) study, the proportion of infected patients within the ICU are often as high as 51%.
  • The Centers for Disease Control and Prevention (CDC) estimated that around 2 million people faces HAIs.
  • In one of the journal named Biomed Central it is mentioned that in United States, every year approximately millions of patients acquire infection.


Florence Nightingale

In 1863, Florence quoted principle of nursing, Hospital design and hygiene.

She also mentioned the importance of hygiene in hospitals in one of her book named “Notes on nursing – What it is and what it is not.”

The book written by Florence Nightingale

Joseph Lister

He was the professor of surgery and he used carbolic acid (phenol) in his surgical techniques and decrease in morbidity and mortality rate.

And from then he was known as “Father of Antiseptic surgery”.

The father of antiseptic surgery – Joseph Lister

Sources of Infections:

Routes of Transmission:     

There are five possible routes of transmission, they are as follows:

  1. Airborne Transmission (TB, Whooping cough, Influenza)
  2. Waterborne Transmission (Dysentery, Cholera, Giardiasis, Gastroenteritis)
  3. Food borne Transmission (Amebiasis, Typhoid)
  4. Contact Transmission (Conjunctivitis)
  5. Vector borne Transmission (Malaria, Dengue, chikungunya)
Contact transmission
Vector borne transmission

Agents of Nosocomial Infections:


Gram positive Bacteria

1. Staphylococcus aureus

It is commonly known to cause lung, heart & bloodstream infections.

Nowadays MRSA (Methicillin Resistant Staphylococcus aureus) and VISA (Vancomycin Intermediate Staphylococcus aureus) is very much common and it is difficult to treat because of their resistance to some antibiotics.

 Therefore are also known as ‘Hospital Staphylococci’ and ‘Super bug’.

2. Clostridium tetani

The spores of C. tetani can survive in dust for long time. Such spores may contaminate cotton, suture materials, plaster of paris. The vegetative spores of C. tetani are usually rod shaped but they became tennis racket or drum stick shaped during forming spores.

The infection caused by this bacteria is usually due to poor sterilization of hospital equipment and environment.

3. Streptococcus pyogenes

S. pyogenes is also known as Group A Streptococcus. They can cause numerous infection with high mortality rate in infants and children.

They severe cause infections like pharyngitis (caused by swelling in back of the throat (pharynx), tonsillitis, scarlet fever (also known as scarlatina, in which bright red rash appears on the body).

Gram Negative Bacteria

1. Enterobacteriaceae

The Enterobacteriaceae family includes bacteria like E.coli, Proteus, Klebsiella, Enterobacter, Serratia.

They generally infect Immunocomproised patients. Some of them are highly antibiotic resistance, especially the Beta Lactam type.

2. Pseudomonas spp.

They can be easily isolated from contaminated or unclean water reservoir. And can also survive and multiply at low temperature & disinfected solutions.

Some of the species may carry drug resistant plasmids.

3. Salmonella typhimurium

The causative agent of typhoid is S. typhimurium and they can easily found in contaminated food and water. It can generally infect intestinal tract and the blood. They can also cause gastroenteritis in humans.


Fungi associated with HAIs

Mucormycosis, now commonly known as black fungus. It is rare but cause highly invasive infection caused by mold called as Mucormycetes. They are generally ubiquitous in nature but affects those people who have health problems or take medicines that lowers the body’s ability to fight against germs.


Viral infections collectively account for 10% of total HAI. Some viruses that are implicated in HAI includes: Respiratory Syncytial Virus (RSV), Corona virus, Hepatitis B and C viruses, HIV, Rotavirus, Herpes Simplex Virus, Influenza virus.


Flies, mosquitoes and fleas can act as a vector or host for many parasites.


  • Entamoeba histolytica -This parasite (protozoa) causes Amoebiasis. It enters in the body through the consumption of contaminated water and food.
  • Plasmodium – This protozoa causes Malaria.
  • Toxoplasma gondii –It is a single celled parasite, causes Toxoplasmosis and acquired through insect bites or stings and through unclean blood products.

Factors affecting HAIs:

  1. Poor condition of hospital
  2. Crowding of patient’s
  3. Contaminated instruments
  4. Immunocomproised patients
  5. Ward & inter or intra hospital transfers
  6. Lack of awareness

Types of Nosocomial Infections:

1. Central line-associated bloodstream infections (CLABSI):

CLABSIs are deadly nosocomial infections with the death incidence rate of 12%–25%.

Catheters are placed in central line to provide fluid & medicines but prolonged use can cause serious bloodstream infections resulting in compromised health and increase in care cost. Once the pathogen enters in the blood it can easily travel to many different organs and can cause infection there.


2. Catheter associated urinary tract infections (CAUTI):

CAUTI is the most usual type of nosocomial infection globally. According to WHO in 2017, UTIs account for more than 12% of reported infections.

Catheters placed inside the bladder through urethra, whereas the imperfect drainage from catheter retains some volume of urine in the bladder providing stability to bacterial residence. CAUTI can develop complications such as orchitis (inflammation of epididymis), epididymitis (inflammation of epididymis) and prostatitis (swelling of prostate gland that produces seminal fluid) in males, and pyelonephritis (inflammation of kidney), cystitis (inflammation of bladder) and meningitis (inflammation of brain and spinal cord membranes called as meninges) in all patients.

3. Surgical site infections (SSI):

SSIs are nosocomial infections occur in 2%–5% of patients subjected to surgery. These are the most common type of nosocomial infections mainly caused by Staphylococcus aureus resulting in prolonged hospitalization and risk of death. The pathogens causing SSI arise from endogenous micro flora of the patient.

4. Nonsurgical site Infection (Wound infection):

It includes ulcers and burns. P.aeruginosa is the most common cause of infection in burns.     

5. Ventilator associated pneumonia (VAP):

VAP is nosocomial pneumonia found in 9–27% of patients on mechanically assisted ventilator. 86% of nosocomial pneumonia is associated with ventilation. Fever, leukopenia and bronchial irritation are common symptoms of VAP. Multidrug resistant S.aureus & Gram negative bacilli are the common pathogens.


HAIs may occur sporadically (occasionally or at irregular intervals) or as an outbreak.

Diagnosis is done by routine bacteriological methods: smears, culture, identification, and sensitivity testing. For identification, sampling is done from the possible sources of infections like: Hospital personnel, inanimate objects, water, air and food.

Diagnosis of HAIs

Problems of Nosocomial Infections:

  1. Addition sufferings
  2. Prolong hospital stay
  3. The cost of care increases
  4. Increase morbidity and mortality rate
  5. Increase emotional stress in patients & their family members
  6. Patient can act as a carrier for various diseases
  7. High Antibiotic resistance

Control of Nosocomial Infections:

  1. One should properly wash their hands with soap.

2. Hospital hygiene is very much important. The linen clothes, bed sheets, pillow covers etc. should be washed regularly.

3. While visiting hospitals, one should always wear mask.

4. Hospital staffs should wear gloves, mask, aprons, caps etc.

5. Vaccination should be compulsory for each of the staff members.

6. Disinfection of inanimate objects, door knobs, handles, elevator buttons etc. is necessary.

7. Discarding of components in proper bags is really important

Puncture proof bag: used needles and syringe

Blue bag: gloves and infected plastic wares

Yellow bag: anatomical waste, placenta, body parts, histological wastes and pathological wastes

Red bag: infected dressing and POP casts

Black bag: cytotoxic drug and chemical waste

Nosocomial Infection Control committee (NICC)- Surveillance:

Surveillance is the systemic and active on-going observations of occurrence & distribution of a diseases within a population. If the incidence or distribution of a disease are known, then the Nosocomial Infection Control committee (NICC) plays an important role in reducing the risk as well as incidence rate.

NICC includes: Physician, Surgeon, Administrator, Microbiologist, Medical Laboratory Technicians, Pharmacist and Housekeeping staff.


Objectives of NICC:

  1. Identifying outbreaks
  2. Identifying risk factors
  3. Informing medical personnel
  4. Evaluate control measures
  5. Providing quality care
  6. Compare hospitals NIC rates

“Soap, Water and Common sense are the best disinfectants in the Hospitals.”  -Sir William Osler


  • Ananthnarayan R. and Jayram paniker C.K. Textbook of Medical Microbiology, 5th Edn.
  • Anderson, D. J. (2011). Surgical site infections. Infectious disease clinics of North America, 25(1), 135-153.
  • Centers for Disease Control and Prevention. (2011). Vital signs: central line-associated blood stream infections—United States, 2001, 2008, and 2009.
  • Ducel, G., Fabry, J., & Nicolle, L. (2002). Prevention of hospital acquired infections: a practical guide. Prevention of hospital acquired infections: a practical guide. (Ed. 2).
  • Hunter, J. D. (2012). Ventilator associated pneumonia.344, e3325.
  • Warren, J. W. (2001). Catheter-associated urinary tract infections. International journal of antimicrobial agents, 17(4), 299-303.
  • Weiner, L. M., Webb, A. K., Limbago, B., Dudeck, M. A., Patel, J., Kallen, A. J & Sievert, D. M. (2016). Antimicrobial-resistant pathogens associated with healthcare-associated infections: summary of data reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2011–2014. Infection control & hospital epidemiology, 37(11), 1288-1301.

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