• Clinical science

Nosocomial infections (Hospital-acquired infections)


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 (MDR) pathogens 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.


Common causative pathogens

Type of infection
Most common pathogens Other causative pathogens
Surgical site infections
Nosocomial pneumonia
Nosocomial urinary tract infections
Bloodstream infections

Risk factors

  • Age > 70 years
  • Lengthy hospital stays → high risk of infection
    • Via medical staff (e.g., insufficient disinfection of hands, clothing) and contact surfaces (e.g., equipment, furniture)
    • Via indoor air (may be contaminated by droplets from infected patients, staff, or procedures like bronchoscopy)
  • Metabolic diseases (especially diabetes mellitus) and immunosuppression
  • Prior antibiotic use
  • Iatrogenic (caused by treatment or a diagnostic procedure)


Overview of multiresistant pathogens

For an overview of the individual drug resistances and treatment options, see “Treatment of multiresistant pathogens” below.

Methicillin-resistant Staphylococcus aureus (MRSA)

The resistance mechanism of MRSA is caused by modified PBPs, not the formation of beta-lactamase! Every detected 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)

  • Definition: A pathogen is termed as MDRGN when resistance is demonstrated to at least three antibiotic classes (see “Treatment of multiresistant pathogens” below).
  • Hospital hygiene and prevention of infection
    • Suspected cases: no isolation
    • In cases of pathogen detection
      • Basic hygiene measures in normal areas sufficient
      • Isolation in risk areas

Infections caused by Pseudomonas aeruginosa


Treatment of multiresistant pathogens

The increased use of antibiotics in hospital settings has led to a greater antibiotic resistance of some bacterial strains. The treatment of infections caused by these strains is difficult since common broad spectrum antibiotics are ineffective and use of alternative drugs is necessary. Therefore, prophylaxis involves both preventing the spread of the causative pathogen as well as treating asymptomatic carriers.

Pathogen Resistance First-line therapy Alternative therapy
Vancomycin-resistant enterococci (VRE)
ESBL pathogens (Extended-spectrum β-lactamase)
Pseudomonas aeruginosa