Lecture 24 - Sterilsation And Infection Flashcards
How can we break the chain of infection?
1\ aseptic technique 2\ antibiotics 3\ Immunisation 4\ Hand washing 5\ Isolate the patient
Where do microorganisms come from?
Hospital environment (instruments, fluid, air, medication)
Invasive devices (IVs, endoscopes, catheters)
Patient’s own flora
Other people
What can we do to the host to break the chain?
Immunisation
Antibiotics
How can we target entry to break the chain of infection?
Aseptic technique
How can we target transmission to break the chain of infection?
Handwashing
Aseptic technique
How can we target the source and pathogen to break the chain of infection?
Sterilising
Isolation of patient
What is aseptic technique?
Procedures that minimise transfer and contamination with potential pathogens
What are the standard (universal) precautions?
Don’t know what the patient has, but we use these precautions just incase
Protective equipment
- masks
- gloves
- gowns
- eyewear
When coming into direct contact with blood, mucous membranes, cuts, bodily fluids
What are the additional precautions?
Minimising risk of cross infection
- single room accommodation (isolation)
- special air filtration
- special respiratory masks
- restricted movement
Why do we encourage hand washing?
Very effective at stopping the spread of organisms
However, not everyone complies
When do we use standard precautions?
What about additional precautions?
Standard:
- all the time
Additional:
- M. tuberculosis
- influenza
When do we use positive and negative pressure rooms?
Positive pressure: highly immunocompromised patient
Negative pressure: TB patients
What are the improvents made in hand hygiene?
Washing: time consuming
Alcohol hand gels: better compliance
DeBug: Austin hospital, even better compliance
What has increased use of antibiotics in hospitals lead to?
Antibiotics resistance:
MRSA
VRE
Acinetobacter spp.
ESBL Klebsiella, E. coli
How can we stem emergence of resistance?
Prudent use of antimicrobials
What do plasmids often carry?
Genes for multiple resistance
Transfer
How does prudent use help?
Avoids selection of mutants
Avoid selection of certain bacteria in the gut
Minimise risk of antibiotic associated diarrhoea (C. difficile)
How can we prevent the spread of infection?
Vaccination
What does disinfection do?
Removes pathogens from an article
What happens when we wash our hands?
Removal of pathogens that have been transiently picked up
We aren’t removing the normal flora that are always there
What is sterilation?
How is this different from sterilisation?
Removal of all living micro-organisms, spores and infectious agents
Wipes out the normal flora as well
What do we call the things that we use for disinfectants?
Disinfectants
What is the difference between biocidal and biostatic?
Biostatic: prevents growth. When removed, they continue to grow
Biocidal: kills bacteria
How do we go about disinfection?
Washing
Hot water, steam
Chemical disinfectants (bleach, alcohols, chlorhexidine, phenols)
- different efficacy against different pathogens
How do we kill spores?
Must use bleach and washing to physically remove the spores
Alcohol is not sufficient
What so we need to think about when disinfecting?
- concentration
- appropriate agent
- appropriate conditions (pH and temperature)
- adequate contact: physical and time
How do we perform sterilisation?
Heat: steam (autoclaves), hot air oven
Filtration: if it is a liquid we are sterilising
Chemical: H2O2, halogens, per acetic acid
Ionizing radiation: for plastic etc.
What do we need to think about when sterilising?
- type of contamination
- rate of biocidal action
- level of assurance
How do we determine the level of contamination?
Viable count
- Dilute out bacteria
- Spread out bacteria on media
- Incubation
- Count the colonies
- Determine initial microbial load
When do we want to mostly affect the bacteria?
In log growth phase
What is the D value?
Time taken to reduce the population tenfold (90%) at a particular temperature
Decimal reduction time
What is sterility assurance?
Probability that a microorganism will survive the killing process
How do we decide on the sterility that is required?
Think about the function of the thing
For example
Bandaid: can accept a lower sterility assurance: 1/1000
Syringe: require higher sterility assurance: 1/1000000
Describe the sterilisation cycle
Preparation Penetration Holding Safety margin Cool down / drying / aeration
What is the sterilisation time?
Penetration + holding
How does heat kill microbes?
Physical and chemical change
Dry: oxidation
Moist: coagulation
Which type of heat is more effective?
Moist heat
Because liberates intense latent heat
Contract is volume –> draws in more heat
Is heat sterilisation good?
- Reliable and available
- economical
- the material must be stable
What can’t we use moist heat for?
Things at risk of Corrosion
Metals
What can we use dry heat for?
Oils, solids, metals
