Healthcare Infections Flashcards
Give some examples of common healthcare infections.
VIRAL = hep. B & C, HIV, norovirus, influenza, chickenpox, SARS
BACTERIAL = Staph. aureus (MRSA), C. difficile, E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Mycobacterium tuberculosis
FUNGAL = Candida albicans, Aspergillus spp.
PARASITIC = malaria
Define healthcare infections.
Infections arising as a consequence of providing healthcare (including infections in hospital visitors & healthcare workers)
Hospital patients: infection is neither present nor incubating at time of admission (practical terms: onset is at least 48hrs after admission)
What are some risk factors for healthcare infections?
Extremes of age, obese/malnourished, diabetes, cancer, immunosuppression, smoking, surgical patients, emergency admission
What are the patient factors in infection prevention and control?
Risk factors:
- optimise patient condition
- hand hygiene
- antimicrobial prophylaxis (before anaesthesia)
- skin preparation before surgery (chlorhexadine in alcohol)
- disinfectant body wash
- MRSA screens
- mupirocin nasal ointment
Interactions with other patients, visitors, & healthcare workers:
- isolation of infected patients (positive air pressure - air comes in only)
- protection of susceptible patients (negative air pressure - air comes out only)
- filtered, sterile air
- vaccinate healthcare workers
- asceptic, non-touch hand hygiene
- personal protective equipment
What are the pathogen factors in infection & control?
Virulence factors
Ecological interactions; including other bacteria, antibiotics, and disinfectants
What are the practice factors in infection & control?
General & specific activities of healthcare workers
Policies, organisation, etc.
What are the place factors in infection prevention & control?
Fixed & variable features of the healthcare environment
- sterile food & food hygiene
- space/layout of ward (Nightingale v.s. single rooms)
- toilets & wash basins
- furniture e.g. no carpets
- single-use equipment, sterilisation, decontamination
- cleaning: disinfectants, steam cleaning, hydrogen peroxide
How do bacteria colonise surfaces?
Adherence via pili/fimbriae which bind to the cell membrane (therefore bacteria without either are unlikely to cause surface infections)
note: although Gram-ve E.coli is the most common cause of sepsis it cannot adhere well to surfaces (rarely indicated in surface infections)
Biofilm formation:
- Bacteria surrounded by polysaccharides, peptides, nucleotides which protects them from antimicrobials & complement
- Facilitated by Quorum sensing
What is Quorum sensing?
Communication between bacteria via autoinducer signalling molecules which bind to cell surface/cytoplasmic receptors on bacteria and stimulate gene expression to initiate co-operative behaviours and produce more autoinducers
Co-operative behaviours include: sporulation, biofilm formation, virulence factor secretion
What are the challenges in treating surface infections?
Adherent organisms are difficult to sample (use ultrasound to shake off biofilm)
Low metabolic state of bacteria (similar to hibernation)
Small colony variants difficult to culture
Poor antibacterial penetration into biofilm
What are some steps that can be taken to avoid contaminating prosthetic surfaces?
Use ultra-clean air (sterilised by filtration)
Use prosthetic surfaces/chemicals designed to discourage biofilm formation e.g. silver in central lines
