Lecture 24 - Sterilsation And Infection

Question 0

How can we break the chain of infection?

Answer 0

1\ aseptic technique
2\ antibiotics
3\ Immunisation
4\ Hand washing
5\ Isolate the patient

Question 1

Where do microorganisms come from?

Answer 1

Hospital environment (instruments, fluid, air, medication)
Invasive devices (IVs, endoscopes, catheters)
Patient’s own flora
Other people

Question 2

What can we do to the host to break the chain?

Answer 2

Immunisation

Antibiotics

Question 3

How can we target entry to break the chain of infection?

Answer 3

Aseptic technique

Question 4

How can we target transmission to break the chain of infection?

Answer 4

Handwashing

Aseptic technique

Question 5

How can we target the source and pathogen to break the chain of infection?

Answer 5

Sterilising

Isolation of patient

Question 6

What is aseptic technique?

Answer 6

Procedures that minimise transfer and contamination with potential pathogens

Question 7

What are the standard (universal) precautions?

Answer 7

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

Question 8

What are the additional precautions?

Answer 8

Minimising risk of cross infection

• single room accommodation (isolation)
• special air filtration
• special respiratory masks
• restricted movement

Question 9

Why do we encourage hand washing?

Answer 9

Very effective at stopping the spread of organisms

However, not everyone complies

Question 10

When do we use standard precautions?

What about additional precautions?

Answer 10

Standard:
- all the time

Additional:

• M. tuberculosis
• influenza

Question 11

When do we use positive and negative pressure rooms?

Answer 11

Positive pressure: highly immunocompromised patient

Negative pressure: TB patients

Question 12

What are the improvents made in hand hygiene?

Answer 12

Washing: time consuming
Alcohol hand gels: better compliance
DeBug: Austin hospital, even better compliance

Question 13

What has increased use of antibiotics in hospitals lead to?

Answer 13

Antibiotics resistance:

MRSA
VRE
Acinetobacter spp.
ESBL Klebsiella, E. coli

Question 14

How can we stem emergence of resistance?

Answer 14

Prudent use of antimicrobials

Question 15

What do plasmids often carry?

Answer 15

Genes for multiple resistance

Transfer

Question 16

How does prudent use help?

Answer 16

Avoids selection of mutants

Avoid selection of certain bacteria in the gut

Minimise risk of antibiotic associated diarrhoea (C. difficile)

Question 17

How can we prevent the spread of infection?

Answer 17

Vaccination

Question 18

What does disinfection do?

Answer 18

Removes pathogens from an article

Question 19

What happens when we wash our hands?

Answer 19

Removal of pathogens that have been transiently picked up

We aren’t removing the normal flora that are always there

Question 20

What is sterilation?

How is this different from sterilisation?

Answer 20

Removal of all living micro-organisms, spores and infectious agents

Wipes out the normal flora as well

Question 21

What do we call the things that we use for disinfectants?

Answer 21

Disinfectants

Question 22

What is the difference between biocidal and biostatic?

Answer 22

Biostatic: prevents growth. When removed, they continue to grow

Biocidal: kills bacteria

Question 23

How do we go about disinfection?

Answer 23

Washing
Hot water, steam
Chemical disinfectants (bleach, alcohols, chlorhexidine, phenols)
- different efficacy against different pathogens

Question 24

How do we kill spores?

Answer 24

Must use bleach and washing to physically remove the spores

Alcohol is not sufficient

Question 25

What so we need to think about when disinfecting?

Answer 25

• concentration
• appropriate agent
• appropriate conditions (pH and temperature)
• adequate contact: physical and time

Question 26

How do we perform sterilisation?

Answer 26

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.

Question 27

What do we need to think about when sterilising?

Answer 27

• type of contamination
• rate of biocidal action
• level of assurance

Question 28

How do we determine the level of contamination?

Answer 28

Viable count

1. Dilute out bacteria
2. Spread out bacteria on media
3. Incubation
4. Count the colonies
5. Determine initial microbial load

Question 29

When do we want to mostly affect the bacteria?

Answer 29

In log growth phase

Question 30

What is the D value?

Answer 30

Time taken to reduce the population tenfold (90%) at a particular temperature

Decimal reduction time

Question 31

What is sterility assurance?

Answer 31

Probability that a microorganism will survive the killing process

Question 32

How do we decide on the sterility that is required?

Answer 32

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

Question 33

Describe the sterilisation cycle

Answer 33

Preparation
Penetration
Holding
Safety margin
Cool down / drying / aeration

Question 34

What is the sterilisation time?

Answer 34

Penetration + holding

Question 35

How does heat kill microbes?

Answer 35

Physical and chemical change
Dry: oxidation
Moist: coagulation

Question 36

Which type of heat is more effective?

Answer 36

Moist heat

Because liberates intense latent heat
Contract is volume –> draws in more heat

Question 37

Is heat sterilisation good?

Answer 37

• Reliable and available
• economical
• the material must be stable

Question 38

What can’t we use moist heat for?

Answer 38

Things at risk of Corrosion

Metals

Question 39

What can we use dry heat for?

Answer 39

Oils, solids, metals