20. Nosocomial infections. Sterilization, disinfection

Definitions
- Nosocomial disease = disease which is the result of treatment in a hospital
- Nosocomial infection (hospital-acquired infection) = infection which is the result of treatment in a hospital
- Nosocomial epidemic = nosocomial infection that affects two or more patients, and there is a connection between the cases
- Commensal bacteria
  - Bacteria which are normally present, but can cause disease in compromised humans
Problems with nosocomial infections
- Many people in small area
- Hospitalized people often have impaired immunity or condition
- Microorganisms in the hospital often have increased resistance to antibiotics
- Microorganisms in the hospital are often more virulent than microorganisms in the community
The primary factors of epidemic process for nosocomial infections
- Source of nosocomial infection
  - The patients themselves
    - From commensal bacteria
  - Other patients
  - Staff
  - Visitors
  - Medical equipment
  - Bedsheets
- Route of transmission
  - Direct contact
  - Indirect
    - Airborne
    - Waterborne
    - Foodborne
    - Objects, instruments
      - Clothing
      - Bedsheets
- Susceptible population
  - High number of susceptible people
  - Infants
  - Elderly
  - Immunocompromised
    - Diabetes
    - Cancer
    - Polytrauma
    - Surgical patients
- Secondary factors
  - Crowded rooms
  - Insufficient number of cleaning and nursing staff
  - Lack of medical staff’s preventive approach
Pathogens
- Bacteria
  - Staph. saprophyticus, Staph. epidermidis
  - E. coli
    - A commensal bacterium
    - May colonize surgical sites, needles, catheters
    - Can be highly antibiotic resistant
  - Clostridium
    - Causes gangrene
  - Staph. aureus, MRSA
    - A commensal bacterium
  - Pseudomonas
    - Likes wet and damp areas
- Viruses
  - Hepatitis B, C
    - Transfusions, dialysis, injections, endoscopy
  - RSV, rotavirus, enterovirus
    - Faecal-oral or hand-to-mouth
- Parasites
  - Giardia lamblia
  - Scabies
- Fungi
  - Often cause infections in immunosuppressed patients
  - Candida albicans
  - Aspergillus
  - Cryptococcus
  - Cryptosporidium
Diseases
- Pneumonia
  - 15% of nosocomial diseases
  - 20 - 50% mortality rate of healthcare-associated pneumonia
  - S. aureus
  - Pseudomonas
  - Klebsiella
  - Risk
    - Intubation
    - Artificial ventilation
- UTI
  - 35% of nosocomial diseases
  - 0,1% mortality
  - E. coli (endogenous)
  - Risk: Catheter
- Surgical site infections
  - S. aureus
  - E. coli
- Sepsis
  - 23% mortality
  - Risk: Infusion/injection
Most commonly affected wards
- Surgery
- ICU
- Paediatrics
Respiratory tract infections and sepsis are the most common cause of mortality in hospitals
Catheters, surgical wounds, intubation, artificial ventilation are common foci where infection can originate

Preventing nosocomial infections

Risk stratification
Reducing person-to-person transmission
- Disinfection of hands
  - Before, during and after patient contact
  - Disinfection = reduce the number of microorganisms, killing most harmful microorganisms
  - Sterilization = kill all microorganisms
- Personal hygiene
- Protective equipment
Preventing transmission from the environment
- Asepsis, antisepsis, isolation of patients
- Sterilization of equipment
- Limit overuse of antibiotics
Education and training of medical staff

Multi-resistant bacteria

MRSA
- Infects skin, wounds, urinary tract, respiratory tract
ESBL – extended spectrum beta lactamase
- Resistant to cephalosporins, penicillins and aztreonam
- Treatment: carbapenems
- Often in E. coli or Klebsiella pneumoniae

For this topic you should also known sterilisation and disinfection in detail (everything from them documenting every step (in case of infection, or a potential lawsuit) what type of methods, phenol-coefficient, Joseph Lister, what kind of methods you would use to sterilize fluids to before you administer it (autoclave), biological indicators, etc. Microbiology 1 covered this.