10 - Nosocomial and Community Infections

• Nosocomial or healthcare associated infection (HCAI) - is defined as an infection developing in a patient as a result of healthcare contact, and had no signs of infection within first 48 hrs of admission.
• Non-nosocomial or community acquired infection (CAI) - is defined as an infection acquired outside the healthcare setting. When in hospital this includes infections diagnosed within 48 hours of admission. (admitted for something else e.g broken bone but developed a fever within 4h hours)
• 7% of hospitalized patients in developed countries acquire a HCAI
• 10% of hospitalized patients in developing countries acquire a HCAI
• 5 main types of nosocomial infections:

  • Central line associated bloodstream infections
  • Catheter associated urinary tract infections (UTI)
  • Nosocomial pneumonia – inc. ventilator associated pneumonia (VAP)
  • Surgical site infections (SSI)
  • Gastrointestinal infection, hygiene and sanitation around food. Hospital outbreaks of Listeria from contaminated food
• Nosocomial pathogens:

  Bacterial:

  Pseudomonas aeruginosa

  Staphylococcus aureus (MRSA)

  Klebsiella spp.

  Enterococcus spp.

  Escherichia coli

  • Clostridium difficile

  Viral:

  • Covid-19
  • Norovirus
• Ventilator associated pneumonia - 19.4% of all nosocomial infections

  Causative agents:

  Pseudomonas aeruginosa: 17.4%

  Staphylococcus aureus: 12.6%

  Klebsiella spp.: 11.4%
• 17.6% of Covid-19 infections are probably HCAIs
• Transmission routes of HCAIs

  1-Endogenous infection – so something the patient may have already had but wasn’t a problem before

  2- Direct transmission between patients.

  3-Direct transmission from patients to HCW

  4- Direct transmission from HCW to patients

  5-Environmental contamination: food and water
• Risk factors for nosocomial infection:

  Environment: poor hygiene, inadequate waste disposal, ventilation, overcrowding, lack of testing, lack of PPE

  Susceptibility: immunosuppression, age, length of stay, drug treatment

  Unawareness/Education: improper injection techniques, inappropriate uses of invasive devises, lack of control policies
• Prevention of HCIAs:

  Environment hygiene, Hand hygiene, Use of PPE, safe use and disposal of sharps, asepsis
• Clostridium difficile is a Gram-positive, toxin-producing, anaerobic bacillus, spore forming (allows it to persist)

  Responsible for a variety of gastrointestinal manifestations ranging from asymptomatic carriage to mild diarrhea, pseudomembranous colitis, and very rarely bowel perforation and death (immunocompromised)

  Transmission: faeco-oral

  Dangerousness Score: 7
• The primary determinant of hospital-acquired CDI was patient severity of illness

  Exposure to both antibiotics and other patients with CDI significantly increased the risk of HA-CDI but this risk was small relative to patient severity of illness
• Risk factors for CDI:

  Antibiotics

  –Significant risk: fluoroquinalones & cephalosporins

  –No associated risk: tetracyclins

  –Associations linked to recent exposure to antibiotics (within four weeks)

  Gastric acid suppressants

  –Proton pump inhibitors (PPIs) appear to be associated

  –Links to disruption of microbiota (dysbiosis)

  Co-morbidities

  –Strong link to inflammatory bowel disease (IBD)

  –Other associations with chronic kidney disease, immunodeficiency and solid organ transplants
• Treatment and control of C. diff

  •Diagnosis

  •Specific antibiotic treatment

  •Isolation

  •Hand hygiene

  •PPE – gloves and apron

  •Bleach cleaning
• Klebsiella spp.

  Gram negative, rod shaped, facultative anaerobe

  2 common species are associated with the majority of human infections: Klebsiella pneumoniae and Klebsiella oxytoca

  Carbapenemase-Producing enterobacteriaceae  (resistant to carbapenem last line antibiotic)

  Dangerousness Score: 5
• Klebsiella pneumoniae

  High mortality of 50% with treatment if it invades the blood

  High fever, chest pain, leukopenia can occur

  Antibiotics can be used but some strains are resistant

  Ubiquitous in nature: found on surface water, sewage, soil and stool is a carrier.
• Klebsiella spp. transmission:

  –Person-to-person contact or, less commonly, by contamination of the environment

  –Patients may be exposed to Klebsiella when they are on ventilators, or have intravenous catheters or wounds (caused by injury or surgery)
• Klebsiella spp. virulence factors:

  • Serum resistance
  • LPS (8 serotypes)
  • Capsule (77 serotypes)
  • Siderophores (molecular iron chelators used to sequester iron from host)
  • Adhesins
• Community Acquired Infections - Anything acquired outside hospital. Infection route include person to person, but also zoonoses, vector borne etc.

  Clostridium difficile Infections (CDIs) & Pneumonia can be examples
• Streptococcus pneumoniae, the most common cause of community acquired pneumonia
• Community acquired C. diff infection risk factors:

  Human contacts: potential in children under 2 years of age and their primary carers

  Food: Retail meats

  Animal: Farmed animals, Some reports of outbreaks in veterinary hospitals, Animal-human or human-animal transmission is biologically plausible

  Environmental: Soil bacteria, contamination of dwellings, Spores residing in kitchens from raw meat
• Streptococcus pneumoniae

  Gram positive, facultative anaerobe, haemolytic

  More than 90 different strains

  Cause invasive (bronchitis) and non-invasive (meningitis and pneumonia) Pneumococcal infections

  Multidrug resistant
• S. pneumoniae

  2 types of vaccine available:

  Pneumococcal conjugate vaccine (PCV) - part of childhood vaccination programme

  Pneumococcal polysaccharide vaccine (PPV) - 65+ or high risk
• Covid-19

  many vaccines, boosters required - efficacy varies (50-95%)
• Pneumonia is both acquired nosocomially and through community; but often the incidence is higher for one organism compared to another; S. pneumoniae high in community  compared to Klebsiella spp.