Nosocomial infection: Encyclopedia II - Nosocomial infection - Pathogens

Nosocomial infection - Pathogens

Nosocomial infection - Bacteria

These are the most common nosocomial pathogens and can be divided into:

• Commensal bacteria found in normal flora of healthy humans. These have a significant protective role by preventing colonization by pathogenic microorganisms. Some commensal bacteria may cause infection if the natural host is compromised. For example, cutaneous coagulase negative staphylococci cause intravascular line infection and intestinal Escherichia coli are the most common cause of urinary infection.
• Pathogenic bacteria have greater virulence, and cause infections (sporadic or epidemic) regardless of host status. For example:
  • Anaerobic Gram-positive rods (e.g. Clostridium) cause gangrene.
  • Gram-positive bacteria: Staphylococcus aureus (cutaneous bacteria that colonize the skin and nose of both hospital staff and patients) cause a wide variety of lung, bone, heart and bloodstream infections and are frequently resistant to antibiotics; beta-haemolytic streptococci are also important.
  • Gram-negative bacteria: Enterobacteriacae (e.g. Escherichia coli, Proteus, Klebsiella, Enterobacter, Serratia marcescens), may colonize sites when the host defences are compromised. They may also be highly resistant.
  • Gram-negative organisms such as Pseudomonas spp. are often isolated in water and damp areas. They may colonize the digestive tract of hospitalized patients.
  • Selected other bacteria are a unique risk in hospitals. For instance, Legionella species may cause pneumonia (sporadic or endemic) through inhalation of aerosols containing contaminated water (air conditioning, showers, therapeutic aerosols).

Nosocomial infection - Viruses

There is the possibility of nosocomial transmission of many viruses, including the hepatitis B and C viruses (transfusions, dialysis, injections, endoscopy), respiratory syncytial virus (RSV), rotavirus, and enteroviruses (transmitted by hand-to-mouth contact and via the faecal-oral route). Other viruses such as cytomegalovirus, HIV, Ebola, influenza viruses, herpes simplex virus, and varicella-zoster virus, may also be transmitted.

Nosocomial infection - Parasites and Fungi

Some parasites (e.g. Giardia lamblia) are transmitted easily among adults or children. Many fungi and other parasites are opportunistic organisms and cause infections during extended antibiotic treatment and severe immunosuppression (Candida albicans, Aspergillus spp., Cryptococcus neoformans, Cryptosporidium). These are a major cause of systemic infections among immunocompromised patients. Environmental contamination by airborne organisms such as Aspergillus spp. which originate in dust and soil is also a concern, especially during hospital construction. Sarcoptes scabies (scabies) is an ectoparasite which has repeatedly caused outbreaks in health care facilities.

Adapted from the Wikipedia article "Pathogens", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki