Nosocomial Infections (Hospital Acquired Infections)

Nosocomial Infections or Hospital Acquired Infections is an infection acquired by the patient from a hospital or other health care facilities.

Recently, a new term, “healthcare-associated infections” is used for the type of infections caused by a prolonged hospital stay and it accounts for a major risk factor for serious health issues leading to death.

Nosocomial Infections (Hospital Acquired Infections)
Nosocomial Infections (Hospital Acquired Infections)

It affects mostly the patients admitted to the hospital, nurses, physicians, aides, visitors, salespeople, and anyone who is in contact with the hospital.

Diseases onset can occur while the patients are still admitted or after their discharge from the hospital.  The situation in which infection is not considered as nosocomial infection are Infections that are incubating when patients are admitted to hospital and Infections that are acquired trans-placental such as syphilis, toxoplasmosis, rubella,  or cytomegalovirus and appear 48hr after birth.

Types of nosocomial infections

1. Central line-associated bloodstream infections (CLABSI)

  • Deadly infection with a death rate of 12-25%
  • To provide fluids and medicines, catheters are introduced in the central line but their continuous use can cause infections in the bloodstream
  • Compromised health and increased care cost
  • An estimated 30,100 CLABSI infections in ICU are reported in the US each year.

2. Catheter-associated urinary tract infections (CAUTI)

  • Most usual type globally
  • Caused due to the presence of native endogenous microflora in patients
  • Catheters introduce bacteria and serve as a conduit but improper drainage of urine retains in the bladed and provides an environment for bacteria to grow.
  • Associated complications include orchitis, epididymitis, prostatitis in males, and pyelonephritis, cystitis, and meningitis in all patients.

3. Surgical site infections (SSI)

  • Takes place in 2-5% of surgery.
  • A second most common type 
  • Caused by Staphylococcus aureus.
  • Result in prolonged hospitalization and death risk
  • Occur from endogenous microflora of patient
  • Incidence: 20% approx, depending on procedure and surveillance.

4. Ventilator-associated pneumonia (VAP)

  • Found in 9-27% of patients on ventilator
  • Happens within 48h of incubation of the trachea.
  • Incidence: 86% of total nosocomial infections
  • Associated symptoms: fever, leucopenia, bronchial sounds.

Nosocomial pathogens

The type of pathogen-associated with nosocomial infection depends upon the patient populations, facilities in the hospital, and the environment.


  • A most common type of pathogens.
  • Arise in immunocompromised patients and involve the natural microflora of the patient.
  • For infection happening in ICU, Acinetobacter is involved, which is a water and soil bacteria and reported for 80% of infections.
  • Bacteroides fragilis: intestine tract and colo, commensal bacteria. Cause infection with other bacteria.
  • Clostridium difficile: transmitted from patient to healthy individual and result in colon inflammation, antibiotic-associated diarrhea, and colitis. It works by eliminating beneficial bacteria with the pathogenic form of itself.
  • Enterobacteriaceae: an infection caused when it travels from the gut to other parts of the body. Includes Klebsiella species and Escherichia coli
  • MRSA or methicillin-resistant Staphylococcus aureus spread through direct contact, contaminated hands, and open wounds. This leads to sepsis, SSI, and pneumonia through traveling from the bloodstream. Resistant to beta-lactam antibiotic.


  • Cause 5% of nosocomial infections
  • Routes of transmission are hand, mouth, respiratory tract, and fecal routes.
  • Most commonly result in hepatitis B and C which is transmitted from healthcare worker to other patients and workers.
  • The least common viruses are influenza, HIV, rotavirus, and herpes simplex virus.


  • Opportunistic pathogens 
  • Infection in immunocompromised patients
  • Aspergillus spp. : cause infection due to contaminated environment, also by inhalation of spores. 
  • Other fungi: Candida albicansCryptococcus neoformans.

Epidemiology of nosocomial infections

  • The effect of nosocomial infection is high in the population globally leading to a high mortality rate which is also associated with financial losses.
  • According to a report by WHO, 15% of approximate hospitalized patients are affected by this infection.
  • 4-56% is the infection mortality rate globally, of which 75% accounts for south-east Asia and sub-Saharan Africa.
  • In high-income countries like the USA, the incidence rate is 3.5%-12% and in low-income countries, it is 5.7-19.1%, which is 3 times higher than in high-income countries.

Pathogenesis of nosocomial infections

  • The nosocomial pathogens that cause diseases come from either endogenous or exogenous sources.
  • Endogenous sources are the patient’s microbiota and 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 caused by an agent derived from the microbiota of the patient, despite whether it became 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).

Diagnosis of nosocomial infections

Diagnosis of different types of nosocomial infection depends on symptoms, infection type, risk factors associated with it, and timing of occurrence of symptoms. 

  1. Central Line-Associated Blood Stream Infection (CLABSI):
  • In the absence of a central venous line, bacteremia should be investigated.
  • If this grows into the central venous line, other infection possibilities are ruled out.
  • Can occur from other sources of infection as well such as wound infection, UTI infection, pneumonia, and endocarditis.
  • The onset of symptoms and their clinical presentation should be observed within 48h of onset.
  1. Catheter-Associated Urinary Tract Infection (CAUTI):
  • Its often get confused with other community-acquired urinary tract infection, but the difference is that it occurs in the presence of the use of a urinary catheter, while later is not.
  • UTIs such as acute cystitis or urethritis can also be diagnosed.
  1. Skin and Soft Tissue Infection (SSI):
  • Fever after the operation can happen in atelectasis with pneumonia, UTI, side effects from medication, and recreation from drugs. 
  • Wound dehiscence, wound herniation, cellulitis, burns, gas gangrene or myonecrosis, tumor or neoplastic process, and septic thrombophlebitis are conditions in which localized pain can be felt.
  • SSI is usually seen after 30-90 days of surgery and its diagnosis requires clinical presentation and diagnostic strategies, such as purulent drainage, positive cultures, or radiographic imaging.
  1. Pneumonia:
  • Diagnosis of community-acquired and hospital-acquired pneumonia also requires the timely recognition of the onset of symptoms. 
  • Hospital-acquired pneumonia shows symptoms after 48h of hospitalization.
  • Diagnosis includes COPD, asthma, pulmonary edema, bronchiectasis, and pulmonary emboli. 
  1. Hospital-Acquired C. difficile Infection (HO-CDI): 
  • Symptom should be correctly differentiated from other infections.
  • Differential diagnoses of antibiotic-associated diarrhea which is not associated with C. difficile, include inflammatory bowel disease, irritable bowel syndrome, malabsorptive diarrhea, and microscopic colitis cause they are noninfectious.
  • Infectious diarrhea is linked to fungi, viruses, and other bacterial pathogens
  • Antibiotic-associated diarrhea can be diagnosed due to the presence of S. aureus, Salmonella, Bacteroides fragilis, Clostridium perfringens, or Klebsiella oxytoca.

Treatments of nosocomial infections

  1. Central Line-Associated Blood Stream Infection (CLABSI)
  • Removal of central venous line catheter should be considered depending on the cultured organism
  • Based on the cultured organism, antimicrobial therapy and the duration of therapy should be determined. 
  • Confirmation of cultured organism should be done a second time.
  • Prevention is the best cure.
  • Skin disinfectants such as chlorhexidine, good hygiene practice, and aseptic technique throughout the procedure must be maintained.
  1. Catheter-Associated Urinary Tract Infection (CAUTI)
  • Catheter management and antimicrobial therapy are needed.
  • The use and duration of indwelling catheters should be minimized. 
  • It is recommended to remove the urinary catheter after 2 weeks due to its ability to form biofilm.
  • To direct initial treatments, providers should use hospital or community antibiograms.
  1. Skin and Soft Tissue Infection (SSI):
  • Devitalized tissues are usually debried in SSI treatment and infected fluids should be drained off. 
  • Anti-microbial therapies are useful.
  • There are various pre-operative measures such as decolonization of specific pathogens, reducing host modifiable risks, etc are necessary.
  • Hair removal or shaving at the site of infection is not necessary as it can introduce microtrauma.
  1. Pneumonia:
  • Reassessment of patients on daily basis is necessary and anti-microbial therapy should be designed.
  • Empiric treatments include P. aeroginosa, MRSA, and other gram-negative bacilli. De-escalation of antibiotics should be done on basis of culture results and clinical stability. 
  • Prevention is always better than cure.
  1. C. difficile infection (CDI)
  • Discontinuation of antibiotics should be done if it is associated with the dosage of the type of antibiotic.
  • Fecal microbiota transplantation
  • Surgical evaluation
  • Prevention such as proper hygiene, clean environment, disinfection, etc. 

Control and prevention 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 technique,  proper handling of equipment, supplies, food, excreta, and surgical wound care and dressings. 
  • To adequately protect their patients, hospital personnel must practice proper aseptic techniques and handwashing procedures and must wear gloves when contacting mucous membranes and secretions. 
  • Patients should be monitored concerning 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 expenses.
  • All hospitals should have a healthcare organization committee that periodically evaluate lab reports, patient charts, and survey to determine whether any increase has occurred in the frequency of particular infectious diseases or potential pathogens.
  • The key factor responsible for the rise in drug-resistant pathogens has been the excessive or inappropriate use of antibiotics and the indiscriminate use of broad-spectrum antibiotics. so there is a need to emphasize alternate prevention and control strategies that prevailed in the years before antimicrobial chemotherapy.
  • Improved sanitation and hygiene, isolation of infected persons, antisepsis, and vaccination should be implemented. 


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