Nosocomial Infections (hospital-acquired infections)

Nosocomial (from the Latin nosocomium meaning hospital) infections are any infections that result in disease when the subject enters the hospital or receives treatment in an outpatient clinic.

Nosocomial Infections (hospital-acquired infections)
Nosocomial Infections (Hospital Acquired Infections)
  • A hospital-acquired infection is another name for this kind of infection (or, more generically, healthcare-associated infections). 
  • Nosocomial infections are those that develop 48 hours or more after hospital admission or within 30 days of discharge.
  • Nosocomial infections can affect patients of all ages, clinical specialties, and anatomical sites.  These infections have the potential to cause fatal outcomes like sepsis and even death. 
  • Increased infections are linked to longer hospital stays, long-term disabilities, higher rates of antimicrobial resistance, socioeconomic unrest, and higher mortality rates. 

Epidemiology of Nosocomial Infections 

  • Nosocomial infections are common. 5.7% of patients had at least one nosocomial infection at any given time, according to a point prevalence survey conducted in 2011–12 among 231,459 patients in 947 acute care hospitals located in 30 different European countries. 
  • Approximately 15% of all hospitalized patients have these infections, according to a WHO estimate. 
  • These infections account for 4%–56% of neonatal deaths overall, with South-East Asia and Sub-Saharan Africa having the highest incidence rates at 75%. (Reference:
  • The incidence ranges from 5.7% to 19.1% in middle and low-income countries, whereas it is sufficiently high in high-income countries (between 3.5% and 12%). 
  • While this incidence is 3–20 times higher in neonates, the overall frequency of infections is three times higher in low-income countries than in high-income countries.

Types of Nosocomial Infections

There are numerous causes of nosocomial infection. They depend on the infection’s type or origin, the pathogen that gave rise to it, and whether it is bacterial, fungal, or viral. The most common types of infections are pneumonia brought on by a ventilator, urinary tract infections brought on by catheters, and infections at surgical sites.

Central line associated bloodstream infections (CLABSIs)

  • CLABSIs are fatal nosocomial infections with a 12% to 25% death rate. 
  • A central line, also known as a central venous catheter, is a tube or catheter that is used to deliver fluids, medications, or blood samples for particular medical tests. 
  • It is typically injected into a large vein in the neck, groin, or chest by doctors. 
  • In intensive care units, doctors most frequently use central lines (ICUs).
  • They can stay in place for weeks or months and access a large vein close to the heart. As a result, they pose a greater risk of serious infection than other intravenous catheters, like IVs.
  • When viruses or bacteria enter the bloodstream through the catheter, a CLABSI, a serious infection, may result.

Catheter associated urinary tract infections (CAUTI)

  • CAUTI is the most common type of nosocomial infection worldwide. 
  • UTIs represent more than 12% of reported infections in acute care hospitals as of 2011. 
  • The patients’ own endogenous native microflora is what causes CAUTIs. 
  • When catheters are placed inside, they act as a channel for bacterial entry, and when the catheter’s imperfect drainage leaves some urine in the bladder, the environment is more stable for bacterial growth. 
  • Male patients may experience orchitis, epididymitis, and prostatitis from CAUTI, while female patients may experience pyelonephritis, cystitis, and meningitis.

Surgical site infections (SSIs)

  • SSIs are nosocomial infections that affect 2-5% of surgical patients. 
  • These are the second most typical type of nosocomial infections and are primarily brought on by Staphylococcus aureus, which increases the risk of death and necessitates prolonged hospitalization. 
  • The pathogens that cause SSI are produced by the patient’s own endogenous microflora. 
  • Depending on the procedure and surveillance criteria used, the incidence could be as high as 20%.

Ventilator associated pneumonia (VAP)

  • Nosocomial pneumonia, or VAP, affects 9 to 27% of patients using a ventilator with mechanical assistance.
  • Typically, it happens 48 hours after tracheal incubation.
  • The cause of 86% of nosocomial pneumonia is ventilation. 
  • VAP symptoms include bronchial sounds, leucopenia, and fever.

Nosocomial Pathogens

Bacteria, viruses, and fungal parasites cause nosocomial infections. These microorganisms differ based on various patient populations, healthcare facilities, and even variations in the environment where care is provided.

Bacteria causing Nosocomial Infections

  • The most frequent pathogens that cause nosocomial infections are bacteria. 
  • Some are a part of the patient’s natural flora and only cause infection when the patient’s immune system becomes vulnerable to infections.
  • The group of pathogenic bacteria called Acinetobacter is what causes infections in intensive care units.
  •  It makes up 80% of the infections that have been reported and is present in both soil and water. 
  • A commensal bacteria called Bacteroides fragilis is found in the colon and gastrointestinal tract. Infections are brought on when other bacteria are present. 
  • Due to the replacement of beneficial bacteria with pathogenic ones, Clostridium difficile causes colon inflammation that results in colitis and diarrhea brought on by antibiotic use.

Viruses causing Nosocomial Infections

  • In addition to bacteria, viruses play a significant role in nosocomial infections. 
  • According to routine monitoring, viruses are responsible for 5% of all nosocomial infections. 
  • They can spread via the hand-mouth, respiratory, and oral-fecal routes. 
  • The virus-based chronic illness is known as hepatitis.
  • Hepatitis viruses can be spread during the delivery of healthcare to both patients and staff. 
  • Unsafe injection practices are a common way to spread hepatitis B and C. 
  • Other viruses include rotavirus, herpes simplex, HIV, influenza, and others.

Fungal parasites causing Nosocomial Infections

  • Fungus parasites act as opportunistic pathogens in people with compromised immune systems, causing nosocomial infections.
  • Infections can be brought on by Aspergillus spp. environmental contamination. 
  • Infections during hospital stays can also be brought on by Candida albicans and Cryptococcus neoformans
  • While Aspergillus infections are brought on by inhaling fungus spores from contaminated air during hospital construction or renovation, Candida infections are brought on by the patient’s own internal flora.

Routes of transmission of Nosocomial Infections

There are 5 main routes of transmission for pathogens;

  1. Contact transmission ( direct or indirect)
  • It is the most significant and frequent way that nosocomial infections are spread. 
  • Microorganisms can be transmitted from one body surface to another or by contaminated instruments, needles, or dressings.
  1. Droplet transmission
  • Droplets are produced by sneezing, coughing, or procedures on the respiratory system like bronchoscopy or suction.
  1. Vector transmission
  • Diseases are spread by insects and other invertebrates (for example, mosquitoes transmit malaria and yellow fever, and fleas transmit plague).
  1. Airborne transmission
  • Dust particles or microscopic (5 micron) droplet nuclei that are suspended in the air.
  1. Common vehicle transmission
  • Transmitted through indirect contact with infected material (e.g., contaminated food, blood products, water, contaminated instruments, and other items).


The environment in which care is provided, the patient’s susceptibility, and the lack of staff and medical professionals’ awareness of such widespread infections are risk factors that affect nosocomial infections.

  1. Environment 
  • Poorly maintained medical facilities and insufficient waste removal.
  1. Susceptibility
  • Long-term use of antibiotics, immune suppression in the patients, and extended ICU stay. 
  1. Unawareness
  • The incorrect use of injection techniques, an inadequate understanding of fundamental infection control procedures, the improper use of invasive devices (such as catheters), and a lack of control policies. 
  • These risk factors are linked to poverty, a lack of financial support, understaffed medical facilities, and an inadequate supply of equipment in low-income countries.

Reservoirs and transmission of Nosocomial Infections

1. Microflora of patient

  • When transferred to tissue wounds or surgical sites, bacteria from the patient’s endogenous flora have the potential to infect the area. 
  • Gram-negative bacteria cause SSI following abdominal surgery in the digestive tract.

2) Patient and staff

  • Pathogen transmission occurs during treatment through direct contact with patients (hands, saliva, other bodily fluids, etc.) and by staff members (water, food, other bodily fluids) during direct contact or through other environmental sources.

3) Environment

  • Water, food, and equipment used in the healthcare industry all contain pathogens that can spread disease. 
  • One more reservoir for uninfected patients is created by transmission to another patient.

Preventions of Nosocomial Infections

Nosocomial infections must be prevented at the outset to stop their spread because they are a significant cause of disease and death.

  1. Transmission from environment 
  • The best environment for the pathogenic organism to thrive in is one that is unhygienic. 
  • Food, water, and the air can all become contaminated and spread to the patients receiving medical care.
  •  Policies must be in place to ensure that beds, baths, toilets, walls, floors, windows, and other medical equipment are cleaned and treated with cleaning agents. 
  • Airborne bacterial contamination can be eliminated with proper ventilation and fresh, filtered air. 
  • Regular maintenance and documentation are required for the ventilation and filter systems in general wards, operating rooms, and intensive care units. 
  • For water analysis, microbiological monitoring techniques should be used. 
  • Separate baths must be given to infected patients. 
  • Foodborne infections may result from improper food handling.
  1. Transmission from staff
  • There is a risk of infection spread by medical staff. 
  • Healthcare professionals have a responsibility to participate in infection control. 
  • Staff members need to practice good personal hygiene, so they should do so.
  • After having contact with infected patients, it is necessary to properly decontaminate your hands with hand disinfectants. 
  • Sterilized tools and safe injection techniques should be applied. 
  • For the delivery of healthcare, the use of masks, gloves, head coverings, and appropriate uniforms is crucial.
  1. Hospital waste management
  • Hospital waste has the potential to act as a pathogen reservoir and must be handled carefully. 
  • Hazardous waste is defined as 10–25% of the waste produced by healthcare facilities. 
  • Waste from healthcare facilities that is infectious should be kept in an area with limited access. 
  • Metal waste, surgical waste, waste from infected people, waste contaminated with blood and sputum, and waste from diagnostic labs must all be disposed of separately.

Control of Nosocomial Infections

Even though there have been significant efforts to prevent nosocomial infections, more work is still needed to control these infections. One out of every 25 hospital patients has a chance of contracting at least one type of nosocomial infection per day.

  1. Infection control programs
  • Healthcare institutions should develop prevention strategies such as immunization campaigns, routine precautions, and transmission-based measures against these infections. 
  • To fulfill their roles in infection prevention, administration, staff, and patients admitted to or visiting hospitals must take these programs into consideration.
  1. Appropriate antimicrobial use
  • In many cases, antibiotics are used to treat illnesses. 
  • The use of antibiotics must be supported by a correct clinical diagnosis of the infection-causing microorganism.
  • According to the Centers for Disease Control and Prevention (CDC), about 50 million of the approximately 100 million courses of antibiotics that are prescribed by doctors in offices each year are unnecessary. 
  • In addition to considering the type of disease and pathogen, the choice of antibiotics should take the patient’s tolerance into account.


It is now more challenging for infection control committees and healthcare administrations to achieve the goal of eliminating intervals due to rising nosocomial infection rates and antimicrobial resistance.

However, it is possible to quickly reduce the resistance of emerging pathogens against antibiotics by implementing sound and healthy methods for care delivery that were designed by infection control committees and controlling the transmission of these infections using appropriate methods for antibiotic use.


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  3. Khan, H. A., Ahmad, A., & Mehboob, R. (2015). Nosocomial infections and their control strategies. Asian Pacific Journal of Tropical Biomedicine, 5(7), 509–514. doi:10.1016/j.apjtb.2015.05.001
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About Author

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Bibita Raut

Bibita Raut has a B.Sc. in Biotechnology. She is a member of Media lab Nepal and Thutto Cycle. She is very interested in studies and research regarding Microbiology, immunology, and food technology.

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