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Hospital-Acquired Infections

Last updated Oct. 3, 2018

Approved by: Krish Tangella MD, MBA, FCAP

Hospital-Acquired Infections, known as HAIs, are a group of common bacteria, fungal, and viral pathogens causing nosocomial infections (infections in a hospital setting).


What are the other Names for this Condition? (Also known as/Synonyms)

  • HAI (Hospital-Acquired Infection)
  • Healthcare-Associated Infections
  • Nosocomial Infections

What are Hospital-Acquired Infections? (Definition/Background Information)

Basic information on Hospital-Acquired Infections is as follows:

  • Hospital-Acquired Infections, known as HAIs, are a group of common bacteria, fungal, and viral pathogens causing nosocomial infections (infections in a hospital setting)
  • These types of pathogens are categorized under Hospital-Acquired Infections and include Methicillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile (c. diff), Staphylococcus aureus, Vancomycin-resistant Enterococci (VRE), Norovirus, Carbapenem-resistant enterobacteriaceae (CRE), and many other pathogens
  • HAIs can occur in immunocompromised individuals, those who are elderly, have undergone major surgery, chemotherapy, or with other conditions that decrease immunity. The signs and symptoms depend upon the location and type of infection
  • HAIs are caused by inadequate hand washing by healthcare providers or through an environment source that could be floating around in the air. Bacteria can exist in the environment despite extensive cleaning
  • Treatment options for prolonged infection include the use of antibiotics and proper medical care. The prognosis depends upon the severity of infection and the medical history of the infected patient

Who gets Hospital-Acquired Infections? (Age and Sex Distribution)

  • Elderly adults and immunocompromised individuals are more susceptible to developing Hospital-Acquired Infections, but they can occur in all age groups
  • Males and females are equally likely to develop HAIs
  • They can occur in all racial and ethnic groups

What are the Risk Factors for Hospital-Acquired Infections? (Predisposing Factors)

The risk factors for Hospital-Acquired Infections include:

  • Patients undergoing chemotherapy
  • Major surgical procedures
  • Poorly controlled diabetes
  • Any medical condition that decreases one’s immunity
  • Patients who use devices such as ventilators, urinary catheters, or intravenous catheters, are at a greater risk of developing HAIs

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Hospital-Acquired Infections? (Etiology)

The causal factors for Hospital-Acquired Infections are dependent upon the type of organism that causes the infection. Common pathogens causing HAIs include:

  • Methicillin-resistant Staphylococcus aureus  (MRSA)
  • Clostridium difficile (c. diff)
  • Staphylococcus aureus
  • Vancomycin-resistant Enterococci (VRE)
  • Norovirus
  • Pseudomonas aeruginosa
  • Vancomycin-resistant Staphylococcus aureus
  • Enterobacteriaceae (carbapenem-resistance)
  • Gram-negative bacteria such as E.coli

These pathogens are responsible for central line-associated bloodstream infections (CLABSI), catheter-associated urinary tract infections (CAUTI), surgical site infections (SSI), ventilator-associated pneumonia (VAP), and many other such infections.

What are the Signs and Symptoms of Hospital-Acquired Infections?

The signs and symptoms of Hospital-Acquired Infections are dependent upon the type of organism that causes the infection and could include:

  • If the pathogen causes a skin infection, a skin abscess may result
  • If the pathogen infects the lungs, symptoms of pneumonia are common
  • If the pathogen affects the heart, symptoms could include rapid heart rate, heart failure, etc.
  • If the pathogen affects the gastrointestinal tract, symptoms could include inflammation, nausea, vomiting, and diarrhea

The most common infection sites include surgical sites, the urinary tract, and the lungs.

How are Hospital-Acquired Infections Diagnosed?

Hospital-Acquired Infections are diagnosed using the following methods:

  • A thorough physical examination, correlated with a complete medical history (including recent surgeries or chemotherapy) can lead to a diagnosis of a Hospital-Acquired Infection
  • Blood tests, blood cultures, and special studies, to identify the specific pathogen
  • Special studies may include molecular testing

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Hospital-Acquired Infections?

Complications due to Hospital-Acquired Infections are dependent on the severity of the infection and the overall immune status of the individual.

  • In a susceptible individual, a prolonged infection usually results if the infection travels to the blood stream, causing blood poisoning (septicemia)
  • Under severe circumstances HAIs may result in death

How are Hospital-Acquired Infections Treated?

The treatment measures for Hospital-Acquired Infections include:

  • Antimicrobial agents specific for the type of pathogen causing infection: Antifungals are used for fungal infections, antibiotics for bacterial infections, and antiviral medications for viruses
  • HAIs that occur at surgical sites are managed with a combination of medication and surgical care
  • Those with gastrointestinal infection must avoid dehydration from severe diarrhea by drinking plenty of water
  • Supplementation of salt and minerals through intravenous fluids for severe vomiting or diarrhea

How can Hospital-Acquired Infections be Prevented?

In many cases, it is difficult to prevent Nosocomial Infections; but, the most common preventive methods for Hospital-Acquired Infections include:

  • Proper hand washing by healthcare professionals
  • Early diagnosis and treatment
  • Advanced cleaning techniques in the hospital environment, including UV light, hydrogen peroxide, use of proper air cleaning, filtration, and ventilation techniques

Extensive laboratory research, surveillance, and outbreak investigations are currently underway in the research community to prevent Hospital-Acquired Infections.

What is the Prognosis of Hospital-Acquired Infections? (Outcomes/Resolutions)

  • The prognosis of HAI is dependent upon the condition of the affected individual. Immunocompromised and elderly individuals are more likely to suffer from prolonged infection
  • The prognosis is generally good when the infection is diagnosed and treated (with medication) early
  • One-third of Hospital-Acquired Infections are considered preventable

Additional and Relevant Useful Information for Hospital-Acquired Infections:

  • The prevalence of Hospital Acquired Infections is greatly varied around the world
  • It is estimated by the Centers for Disease Control and Prevention (CDC) that 2 million individuals in the United States are infected by Hospital-Acquired Infections each year. Of these 2 million individuals infected, approximately 20,000 cases result in death

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: April 29, 2015
Last updated: Oct. 3, 2018