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Hospital-acquired infections

Last updated: September 29, 2021

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Hospital-acquired infections (HAIs), also called nosocomial infections, are infections that are contracted 48 hours after hospitalization and that were not present or incubating at the time of admission. HAIs are transmitted through patient exposure to health care workers, other patients, hospital equipment, or interventional procedures. The most common types of HAIs include intravascular catheter-related bloodstream infection (CRBSI), catheter-related urinary tract infection (CAUTI), hospital-acquired pneumonia, ventilator-associated pneumonia, surgical site infection (SSI), and Clostridioides difficile infection (CDI). The most common causative pathogens differ based on the site of infection (e.g., gastrointestinal tract, urinary tract, lungs, skin). An increasing number of HAIs are caused by multidrug-resistant organisms (MDROs). Common MDROs include methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum beta-lactamase-producing bacteria (ESBL), and vancomycin-resistant enterococci (VRE). The preferred antibiotic therapy for an MDRO infection should be guided by the antibiogram, ideally in consultation with an infectious disease specialist.

This article provides an overview of the diagnosis and management of common HAIs. Prevention of nosocomial infections is covered separately. See also “Intravascular catheter-related bloodstream infection.”

  • Hospital-acquired infection (nosocomial infection): an infection acquired after > 48 consecutive hours of hospitalization that was not present or incubating at admission
  • Health care-associated infection (HCAI): an infection that develops after receiving health care in any setting (including a hospital, long-term care facility, nursing home, ambulatory care clinic, home care, or surgical intervention)

Reference: [1]

Risk factors [2][3][4][5]

Common causative pathogens [5]

Overview of hospital-acquired infections [1][7]
Conditions Risk factors Diagnostic criteria [1] Initial management steps
Intravascular catheter-related bloodstream infection [8]
Catheter-associated urinary tract infection
(CAUTI) [9]
  • Prolonged urinary catheterization (suprapubic, urethral, or condom)
  • Symptomatic culture-proven infection of the urinary tract system
  • AND a urinary catheter in place for > 48 consecutive hours OR within 48 hours after removal of a urinary catheter
  • AND and no other source of infection
Nosocomial pneumonia [10][11]
Surgical site infection
  • An infection of the incision, organ, or space involved in a preceding surgical procedure [1][13]
  • Onset of symptoms postoperatively: [1]
    • Superficial incisional infections: within 30 days
    • Deep incisional, organ, and space infections: within 30–90 days
Clostridioides difficile infection [14][15][16][17]
  • Diagnosis requires the following: [14][15][20]
    • Typical clinical features
    • Objective confirmation of infection

Consider HAIs in patients who have recently been hospitalized or undergone a medical intervention and present with new-onset infectious symptoms (e.g., fever, cough, dysuria, pus, diarrhea) and/or unexplained clinical deterioration (e.g., hypotension, increased ventilator support, altered mental status). The approach to management may vary depending on the site of infection and is covered in detail in dedicated articles. The general approach to a suspected HAI is briefly described here.

Reference: [1]

Definition [21]

Pathogens (usually bacteria) that are resistant to ≥ 1 antimicrobial agent.

Risk factors [21]

  • Prolonged hospitalization, especially in the ICU
  • Prior antibiotic use
  • Indwelling medical devices
  • Exposure to other individuals with MDROs (e.g., long-term care facilities)

Common pathogens

Methicillin-resistant Staphylococcus aureus (MRSA)

The resistance mechanism of MRSA relies on modified PBPs, not the formation of beta-lactamase. Every case of MRSA (symptomatic or asymptomatic) requires treatment.

Extended-spectrum beta-lactamase-producing bacteria (ESBL)

Vancomycin-resistant enterococci (VRE)

Multidrug-resistant gram-negative bacteria (MDRGNB) [23]

  • Definition: gram-negative pathogens that are resistant to at least three of the four main antibiotic classes
  • Measures
    • Suspected cases: no isolation
    • Confirmed cases
      • Basic hygiene measures in low-risk areas are sufficient.
      • Isolation in risk areas (e.g., ICU, neonatology, hematology-oncology)

Pseudomonas aeruginosa

Management [21][24][25]

  • Management of infections with MDROs is often complicated by limited antibiotic options.
  • Select antibiotic agents based on the antibiogram, preferably in consultation with an infectious disease specialist.
  • Antibiotics to which the MDRO has some resistance may still be used but at higher doses and/or increased frequency. [26]
  • Combination therapy with multiple antibiotic agents may be needed.
  • Antibiotic stewardship programs may require infectious disease approval for certain medications.

Antibiotic regimens for the same pathogen may differ based on the source of infection and the severity of the disease.

Treatment of multiresistant pathogens
Pathogen Resistance First-line therapy Alternative therapy
Gram-positive MRSA [27]
Vancomycin-resistant enterococci (VRE)
Gram-negative ESBL pathogens (extended-spectrum β-lactamase)
Pseudomonas aeruginosa
  1. National Healthcare Safety Network (NHSN) Patient Safety Component Manual.
  2. Yokoe DS, Anderson DJ, Berenholtz SM, et al. A Compendium of Strategies to Prevent Healthcare-Associated Infections in Acute Care Hospitals: 2014 Updates. Infect Control Hosp Epidemiol. 2014; 35 (8): p.967-977. doi: 10.1086/677216 . | Open in Read by QxMD
  3. O’Grady NP, Alexander M, Burns LA, et al. Guidelines for the Prevention of Intravascular Catheter-related Infections. Clin Infect Dis. 2011; 52 (9): p.e162-e193. doi: 10.1093/cid/cir257 . | Open in Read by QxMD
  4. Hooton TM, Bradley SF, Cardenas DD, et al. Diagnosis, Prevention, and Treatment of Catheter-Associated Urinary Tract Infection in Adults: 2009 International Clinical Practice Guidelines from the Infectious Diseases Society of America. Clin Infect Dis. 2010; 50 (5): p.625-663. doi: 10.1086/650482 . | Open in Read by QxMD
  5. Kalil AC, Metersky ML, Klompas M, et al. Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016; 63 (5): p.e61-e111. doi: 10.1093/cid/ciw353 . | Open in Read by QxMD
  6. Klompas M, Branson R, Eichenwald EC, et al. Strategies to Prevent Ventilator-Associated Pneumonia in Acute Care Hospitals: 2014 Update. Infect Control Hosp Epidemiol. 2014; 35 (8): p.915-936. doi: 10.1086/677144 . | Open in Read by QxMD
  7. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014; 59 (2): p.e10-52. doi: 10.1093/cid/ciu444 . | Open in Read by QxMD
  8. Berríos-Torres SI, Umscheid CA, Bratzler DW, et al. Centers for Disease Control and Prevention Guideline for the Prevention of Surgical Site Infection, 2017. JAMA Surgery. 2017; 152 (8): p.784. doi: 10.1001/jamasurg.2017.0904 . | Open in Read by QxMD
  9. Cohen SH, Gerding DN, Johnson S, et al. Clinical Practice Guidelines for Clostridium difficile Infection in Adults: 2010 Update by the Society for Healthcare Epidemiology of America (SHEA) and the Infectious Diseases Society of America (IDSA). Infect Control Hosp Epidemiol. 2010; 31 (05): p.431-455. doi: 10.1086/651706 . | Open in Read by QxMD
  10. McDonald LC, Gerding DN, Johnson S, et al. Clinical practice guidelines for clostridium difficile infection in adults and children: 2017 update by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA). Clin Infect Dis. 2018; 66 (7): p.e1-e48. doi: 10.1093/cid/cix1085 . | Open in Read by QxMD
  11. Khanna S, Gupta A. Community-acquired Clostridium difficile infection: an increasing public health threat. Infection and Drug Resistance. 2014 : p.63. doi: 10.2147/idr.s46780 . | Open in Read by QxMD
  12. Issa M, Ananthakrishnan AN, Binion DG. Clostridium difficile and inflammatory bowel disease. Inflamm Bowel Dis. 2008; 14 (10): p.1432-1442. doi: 10.1002/ibd.20500 . | Open in Read by QxMD
  13. Hickson M. Probiotics in the prevention of antibiotic-associated diarrhoea and Clostridium difficile infection. Therap Adv Gastroenterol. 2011; 4 (3): p.185-197. doi: 10.1177/1756283X11399115 . | Open in Read by QxMD
  14. Deshpande A, Pasupuleti V, Thota P, et al. Community-associated Clostridium difficile infection and antibiotics: a meta-analysis. J Antimicrob Chemother. 2013; 68 (9): p.1951-1961. doi: 10.1093/jac/dkt129 . | Open in Read by QxMD
  15. Carey-Ann BD, Carroll KC. Diagnosis of Clostridium difficile Infection: an Ongoing Conundrum for Clinicians and for Clinical Laboratories. Clin Microbiol Rev. 2013; 26 (3): p.604-630. doi: 10.1128/cmr.00016-13 . | Open in Read by QxMD
  16. Siegel JD, Rhinehart E, Jackson M, Chiarello L, Healthcare Infection Control Practices Advisory Committee.. Management of multidrug-resistant organisms in health care settings, 2006.. Am J Infect Control. 2007; 35 (10 Suppl 2): p.S165-93. doi: 10.1016/j.ajic.2007.10.006 . | Open in Read by QxMD
  17. Wielders CLC, Fluit AC, Brisse S, Verhoef J, Schmitz FJ. mecA Gene Is Widely Disseminated in Staphylococcus aureus Population. J Clin Microbiol. 2002; 40 (11): p.3970-3975. doi: 10.1128/jcm.40.11.3970-3975.2002 . | Open in Read by QxMD
  18. New Guidelines Available on the Prevention and Control of Multi-Drug-Resistant Gram-Negative Bacteria in Hospitals. Updated: November 18, 2015. Accessed: February 12, 2017.
  19. Liu C, Bayer A, Cosgrove SE et al. Clinical Practice Guidelines by the Infectious Diseases Society of America for the Treatment of Methicillin-Resistant Staphylococcus Aureus Infections in Adults and Children. Clin Infect Dis. 2011; 52 (3): p.e18-55. doi: 10.1093/cid/ciq146 . | Open in Read by QxMD
  20. Zilahi G, Artigas A, Martin-Loeches I. What’s new in multidrug-resistant pathogens in the ICU?. Ann Intensive Care. 2016; 6 (1). doi: 10.1186/s13613-016-0199-4 . | Open in Read by QxMD
  21. Kowalska-Krochmal B, Dudek-Wicher R. The Minimum Inhibitory Concentration of Antibiotics: Methods, Interpretation, Clinical Relevance. Pathogens. 2021; 10 (2): p.165. doi: 10.3390/pathogens10020165 . | Open in Read by QxMD
  22. Choo EJ, Chambers HF. Treatment of Methicillin-Resistant Staphylococcus aureus Bacteremia. Infection & Chemotherapy. 2016; 48 (4): p.267. doi: 10.3947/ic.2016.48.4.267 . | Open in Read by QxMD
  23. Multi-Drug Resistant Gram Negative Bacilli (MDRGNB). Updated: February 12, 2017. Accessed: February 12, 2017.
  24. WHO Guidelines on Hand Hygiene in Health Care: a Summary. Updated: January 1, 2009. Accessed: February 12, 2017.
  25. National and State Healthcare Associated Infections Progress Report 2016. Updated: March 3, 2016. Accessed: February 12, 2017.
  26. Inweregbu K, Dave J, Pittard A. Nosocomial infections. Continuing Education in Anaesthesia Critical Care & Pain. 2005; 5 (1): p.14-17. doi: 10.1093/bjaceaccp/mki006 . | Open in Read by QxMD
  27. Magill SS, O’Leary E, Janelle SJ, et al. Changes in Prevalence of Health Care–Associated Infections in U.S. Hospitals. N Engl J Med. 2018; 379 (18): p.1732-1744. doi: 10.1056/nejmoa1801550 . | Open in Read by QxMD
  28. Chiche L, Forel J-M, Papazian L. The role of viruses in nosocomial pneumonia. Curr Opin Infect Dis. 2011; 24 (2): p.152-156. doi: 10.1097/qco.0b013e328343b6e4 . | Open in Read by QxMD