Nosocomial Infection

What Is It, Causes, Prevention, and More

Author: Jennifer Cheung, RN

Editors: Antonella Melani, MD, Ahaana Singh, Lisa Miklush, PhD, RN, CNS

Illustrator: Abbey Richard

What is a nosocomial infection?

Nosocomial infections, also called health-care-associated or hospital-acquired infections, are a subset of infectious diseases acquired in a health-care facility. To be considered nosocomial, the infection cannot be present at admission; rather, it must develop at least 48 hours after admission. These infections can lead to serious problems like sepsis and even death. 

Often, nosocomial infections are caused by multidrug-resistant pathogens acquired via invasive procedures, excessive or improper antibiotic use, and not following infection control and prevention procedures. In fact, many nosocomial infections are preventable through guidance issued by national public health institutes such as the Centers for Disease Control and Prevention (CDC). 

Who is at risk for a nosocomial infection?

Factors that increase the risk for a nosocomial infection include increasing age, length of hospitalization, excessive or improper use of broad-spectrum antibiotics, and the number of invasive devices and procedures (for instance: central venous catheters, urinary catheters, surgical procedures, and mechanical ventilation). In addition, most patients often have accompanying conditions such as diabetes, chronic lung disease, renal insufficiency, or malnutrition. 

What is the most common type of nosocomial infection?

Though various bacteria, viruses, and fungi can all cause nosocomial infections, the most common is the bacterium Staphylococcus aureus. Other common pathogens like Escherichia coli, Enterococci, and Candida are common culprits, and all can be normally found on the skin and mucous membranes. Antibiotic-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA) can be especially dangerous and difficult to treat.

Urinary catheters

A urinary catheter is a tube inserted into the bladder to collect urine into a closed collection system. Urinary catheters can help patients who have difficulty controlling or emptying their bladder. As patients under anesthesia are unable to control their bladder, urinary catheters are typically placed during surgical procedures to keep the bladder empty.

Pathogens spread through an individual’s perineum or a contaminated urinary catheter can lead to urinary tract infections, which are the most common nosocomial infections. Symptoms of urinary tract infections include painful urination, flank pain, and fever.

Surgical procedures

The second most common nosocomial infection are surgical site infections that can develop after surgery. The length of operation, surgical technique, and operating room sterility are all factors that can affect the incidence of surgical site nosocomial infections. 

Surgical site infections are caused by pathogens already prevalent on the skin or by organisms shed from members of the operating room staff, and often involve the skin, organs, or implanted materials. Symptoms may include skin redness, tenderness, and drainage from surgical sites.

Central venous catheters

A central venous catheter (also known as a central line) is a tube placed in a large vein in the neck, arm, chest, or groin and can remain in place indefinitely. Central venous catheters can be used to give intravenous therapies such as total parenteral nutrition (TPN), which provides nutrients and fluids to patients. Bloodstream infections can result from pathogens that may penetrate the skin during insertion of hubs of central lines. This is the third most common form of nosocomial infection and has the highest rate of mortality. Symptoms of infection may include skin redness, tenderness, and drainage at insertion sites.

Mechanical ventilation

Ventilator-associated pneumonia is a respiratory infection caused by breathing in contaminated oropharyngeal flora during mechanical ventilation (machine-assisted breathing). Together with central-line bloodstream infections, it is the third most common nosocomial infection. Early-onset nosocomial pneumonia occurs within the first four days of admission and is commonly caused by community-acquired pathogens like Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae. Late-onset pneumonia is frequently caused by multi-drug resistant bacteria like MRSA, Pseudomonas aeruginosa, Klebsiella, and Acinetobacter. Signs and symptoms include fever, increased mucus production, increased white blood cell count, and abnormal chest X-ray findings.

How can nosocomial infections be prevented?

Prevention of nosocomial infections begins with health-care facilities implementing infection control protocols to reduce exogenous and endogenous transmission. 

Exogenous transmission occurs due to person-to-person interactions and through environmental cross-contamination. Frequent hand hygiene is the most important preventative measure to limit the spread of pathogens. Other measures include compliance with isolation precautions and proper use of personal protective equipment. Additionally, health-care providers should avoid unnecessary use of indwelling devices, and remove them as soon as advisable. Finally, reducing environmental transmission involves practicing proper aseptic and/or sterile techniques during insertion and maintenance of devices. For instance, the routine disinfection of surfaces, patient equipment, and medical devices—as well as appropriate waste management—are important measures in preventing the exogenous transmission of nosocomial infections. 

Endogenous transmission comes from excessive and improper use of broad-spectrum antibiotics. For instance, vancomycin affects the normal balance in the patient's own endogenous bacterial flora, ultimately leading to an overgrowth of some bacteria. Endogenous transmission can also occur as a transfer from one part of the body to the other (as with urinary tract infections), or if the patient's immune system is depressed by factors like malnourishment or chemotherapy. Appropriate antimicrobial use with the correct agent, dose, and duration is needed to minimize the growth of antibiotic-resistant pathogens.

How can surgeons help limit nosocomial infections?

Surgical site infections can be limited via methods such as regularly disinfecting surfaces, restricting staff entry, minimizing movement of sterile drapes, and appropriate use of surgical attire. Additionally, preoperative antimicrobial patient bathing and administration of prophylactic antimicrobials have been shown to decrease infections.

What are the most important facts to know about nosocomial infections?

Nosocomial infections are infections patients acquire while admitted to a health-care facility and generally develop 48 hours or later after admission. These infections can lead to serious problems like sepsis and even death. Most nosocomial infections are preventable, with prevention guidelines set by national public health institutes such as the Centers for Disease Control and Prevention (CDC).

The risk of developing a nosocomial infection partially depends on how strictly health-care facilities follow infection control guidelines. Patients at increased risk of infection include those with comorbid conditions, increased age, recent treatment with antibiotics, and prolonged hospitalizations. The most common type of nosocomial infection involves invasive devices and procedures (urinary catheters, central lines, mechanical ventilation, or surgery). 

Nosocomial infection prevention requires health-care facility-wide adaptation of stringent infection control programs with ongoing surveillance to identify and control outbreaks. Surgeons can limit nosocomial infections by implementing protocols that improve surgical technique, control operating room environment, limit organisms shed by the operating room staff, and decrease length of operation, as well as recognizing underlying patient factors that may increase the risk of a nosocomial infection.

Related links

High Yield: Pneumonia
Clinical Reasoning: Pneumonia
Staphylococcus aureus
Pseudomonas aeruginosa
Klebsiella pneumoniae
Streptococcus pneumoniae
Knowledge Shot: Hand Washing

Resources for research and reference

Anderson, D. J., Podgorny, K., et al. (2014). Strategies to Prevent Surgical Site Infections in Acute Care Hospitals: 2014 Update. (2014). Infection Control and Hospital Epidemiology, 35(6): 605–627. DOI: 10.1086/676022

Jameson, J. L., Fauci, A. S., Kasper, D. L., Hauser, S. L., Longo, D. L., & Loscalzo, J. (2018). Harrison’s Principles of Internal Medicine (20 edition). New York, NY: McGraw-Hill.

Klompas, M., Branson, R., et al. (2014). Strategies to Prevent Ventilator-Associated Pneumonia in Acute Care Hospitals: 2014 Update. (2014). Infection Control and Hospital Epidemiology, 35(8): 915–936. DOI: 10.1086/677144

Lo, E., Nicolle, L. E., et al. (2014). Strategies to Prevent Catheter-Associated Urinary Tract Infections in Acute Care Hospitals: 2014 Update. Infection Control and Hospital Epidemiology, 35(5): 464–479. DOI: 10.1086/675718

Marschall, J., Mermel, L. A., et al. (2014) Strategies to Prevent Central Line-Associated Bloodstream Infections in Acute Care Hospitals: 2014 Update. Infection Control and Hospital Epidemiology, 35(7): 753–771. DOI: 10.1086/676533

Papadakis, M. A. & McPhee, S. J. (2020). Current Medical Diagnosis and Treatment (59 edition). New York, NY: McGraw-Hill.

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Prevention of hospital-acquired infections: A practical guide 2nd edition. (2002). In World Health Organization. Retrieved August 22, 2020, from