Disinfectants, Antiseptics and Preservatives Flashcards
What is the definition of disinfection?
The process of removing micro-organisms from surfaces of inanimate objects
What are the properties of good Disinfectants?
Broad spectrum Rapid kill Non corrosive Easy to prepare and use Stable Inexpensive
What are high-level disinfectants?
They destroy ALL micro-organisms
What are intermediate-level disinfectants?
They destroy all bacteria, most viruses and fungi
Exclude some viruses, bacterial spores, prions
What are low-level disinfectants?
They destroy most bacteria, some viruses, fungi
Excludes TB, some viruses, fungi, bacterial spores, prions
What are examples of high-level disinfectants?
Aldehydes
Hypochlorites
Peroxydens
What are examples of intermediate-level disinfectants?
Alcohols Biguanides Iodine/Iodophore Phenolics QACs
What are examples of low-level disinfectants?
Phenolics
What are the main factors affecting choice of disinfectant?
Intended application No. and type of micro-organisms present Environmental factors Safety, Stability and Cost Properties of chemical agent
What types of disinfectants are critically toxic?
Phenolics and Aldehydes (formaldehyde and gluteraldehyde)
Unstable compounds are stored in what form before use?
Inactive
Activated before use
How does organic matter (blood, pus, food residues) affect disinfectants?
They can decrease antimicrobial capacity
How do divalent cations (Ca and Mg) affect disinfectants?
They decrese the activity of them
Stabilize cell well, block adsorption sites
How does dilution affect disinfection?
Higher conc. of disinfectant increases efficacy and decreases exposure time.
Dilution doesn’t affect all disinfectants in the same way:
- The higher the N (dilution coefficient) the bigger the decrease in potency by dilution
How does temperature affect disinfection?
Cidal activity is increased with increased temperature
Expressed quantitatively by calculating temperature coefficient (Q10)
Dependent on chemical
How does pH affect disinfection?
Affects survival and growth of organism
Affects potency
The disinfectant must remain ‘___’
Wet
What is the suspension test?
Dilutions of disinfectant added to standardised bacterial suspension in water + albumin at set temp
At a specific time interval:
- Remove sample
- Neutralise disinfectant
- Determine viable count (cfu/ml)
Calculate conc. disinfectant req. to kill 99.999% (5 log kill, 1 in 100,000 bacteria survive)
How do you work out the minimum inhibitory concentration (MIC)?
- Prepare doubling dilutions of test agent
- Inoculate with test organism
- Incubate at 37C overnight
- Score for growth
MIC is the lowest conc. showing no growth
What is the disc susceptibility test?
Zone of growth inhibition indicates antimicrobial activity.
Compare to standards.
What do antiseptics do?
Destroy or inhibit micro-organisms on living tissue
How are antiseptics evaluated?
Time Kill.
For each micro-organism and each antimicrobial:
- Dilute test agent
- Inoculate with test organism
- At designated time intervals, remove the sample and determine the viable count (antimicrobial needs to be neutralised)
What do preservatives do?
Decrease microbial spoilage AFTER product manufacture
- Decrease risk of infection
What factors affect the choice of a preservative?
Intended application
- Sterile/Non-sterile
- Route of admin (affects toxicity)
- Composition of product/packaging (susceptibility to microbial attack)
No. and type of micro-organisms present
Micro-environment
Safety, Stability, Cost
Properties of chemical agent (interactions with other components)
- Capacity
- Conc/dilution
- Storage temperature
- pH
How are preservatives evaluated?
Challenge test.
- Assess activity with product in final container
- Inoculate preserved product with 10^6 test organisms per ml
- Assess viability by VC
- Preservative adequate if decrease in viability meets criteria of acceptance (diff criteria for diff preservatives)
What are the properties of good Preservatives?
Adequate spectrum Rapid and/or long term action Good solubility Effective at product pH Compatible with formulation/packing Physically undetectable Constitute a small proportion of product Stable, non-toxic and cost effective
What are the properties of good Antiseptics?
Adequate spectrum Rapid Kill Non-toxic, non-irritant Immediate, persistent and cumulative activity Motivation to use Stable, cost effective
