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Nosocomial infections

Last updated: November 11, 2020

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Nosocomial infections, also known as hospital-acquired infections, are newly acquired infections that are contracted within a hospital environment. Transmission usually occurs via healthcare workers, patients, hospital equipment, or interventional procedures. The most common sites of infection are the bloodstream, lungs, urinary tract, and surgical wounds. Though any bacteria may cause a nosocomial infection, there is an increasing incidence of multidrug-resistant pathogens (MDR) causing hospital-acquired infections. This rise can be explained by indiscriminate use of antibiotics and lacking hygiene measures, especially among medical staff. Commonly seen multidrug-resistant pathogens include methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum beta-lactamase-producing bacteria (ESBL), and vancomycin-resistant enterococci (VRE). The choice of antibiotic for treating infections with these pathogens is based on the individual resistance profile and often requires additional strict isolation methods for the patient.

  • Nosocomial infections are defined as infections acquired after hospitalization and occur within 48 hours of hospital admission, 3 days of discharge or 30 days of an operation. [1]
  • At admission, these infections are not present or incubating.

Common causative pathogens [2]

Risk factors [1][2][3]

  • Age > 70 years
  • Lengthy hospital stays → ↑ risk of infection
    • Medical staff (e.g., insufficient disinfection of hands, clothing)
    • Contact surfaces (e.g., equipment, furniture)
    • Indoor air (e.g., via contaminated by droplets from infected patients, staff, procedures like bronchoscopy)
  • Iatrogenic: caused by treatment or a diagnostic procedure
  • Prior antibiotic use
  • Metabolic diseases (especially diabetes mellitus)
  • Immunosuppression

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) [5]

  • 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 normal areas sufficient
      • Isolation in risk areas (e.g., intensive care, neonatology, hematology-oncology)

Pseudomonas aeruginosa

Treatment of multiresistant pathogens [6]
Pathogen Resistance First-line therapy Alternative therapy
Vancomycin-resistant enterococci (VRE)
ESBL pathogens (extended-spectrum β-lactamase)
Pseudomonas aeruginosa

References: [8][9][10]

  1. 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
  2. Multi-Drug Resistant Gram Negative Bacilli (MDRGNB). Updated: February 12, 2017. Accessed: February 12, 2017.
  3. O’Grady NP, Alexander M, Burns LA, et al. Guidelines for the Prevention of Intravascular Catheter-related Infections. Clinical Infectious Diseases. 2011; 52 (9): p.e162-e193. doi: 10.1093/cid/cir257 . | Open in Read by QxMD
  4. Shah H, Bosch W, Thompson KM, Hellinger WC. Intravascular Catheter-Related Bloodstream Infection. The Neurohospitalist. 2013; 3 (3): p.144-151. doi: 10.1177/1941874413476043 . | Open in Read by QxMD
  5. Rupp ME, Karnatak R. Intravascular Catheter–Related Bloodstream Infections. Infect Dis Clin North Am. 2018; 32 (4): p.765-787. doi: 10.1016/j.idc.2018.06.002 . | Open in Read by QxMD
  6. 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
  7. 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.
  8. National and State Healthcare Associated Infections Progress Report 2016. Updated: March 3, 2016. Accessed: February 12, 2017.
  9. WHO Guidelines on Hand Hygiene in Health Care: a Summary. Updated: January 1, 2009. Accessed: February 12, 2017.
  10. 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