Antiseptics and Disinfectants Flashcards
Antiseptic VS Disinfectant
Antiseptic
- dermal application to mucous membranes of animal/ person
- kill/ inhibit growth of m.o
- minimise risk of clinical infection
- not for internal use
Disinfectant
- use on inanimate object
- kill m.o
- not for internal use
Properties
- Broad spectrum
- not inactivated by organic matters/ water
- Retain activity after rinsing
- odourless, colour less
Factors affecting effectiveness
- Number and type of m.o
- Exposure time
- Exposure temp
- Temperature coefficient Q: effect of temperature increase on rate of inactivation (normally Q10)
10 deg C increase in temp - Concentration of antimicrobial agent
- Dilution coefficient n: rate of killing decreases with dilution of disinfectant
- low ‘n’ means disinfectant is less affected by dilution
t1c1^n = t2c2^n - pH of treatment
- affects ionisation state and influence on activity, stability - Presence of extraneous materials
- organic contaminants e.g. blood, faeces can protect m.o from disinfectants
- need to take these into account when calculating concentration of disinfectant
Minimum inhibitory concentration
Lowest concentration that can inhibit growth of m.o
Test: Use disinfectant at various conc mixed with nutrient broth in test tubes, inoculate tubes and incubate to detect growth, lowest conc to show no growth is the MIC value
Capacity Test
Test for ability to retain activity in the presence of increasing m.o load
- Bacterial suspension mixed with ‘in use’ dilution of disinfectant
- After exposure period second and third additions of bacterial suspension into disinfectant
- Subculture in broths to detect growth
Phenol coefficient test (rideal walker)
A measure of bactericidal activity of a chemical compound in relation to phenol
- highest dilution of test compound that kills the test organism compared to the concentration of phenol that kills the test organism under the same conditions
Dilution factor of test disinfectant/ dilution factor of phenol
Phenolic Disinfectants
- Cell wall damage, cytoplasmic membrane leakage, protein coagulation
- not sporicidal
- high dilution coefficient
- inactivated by dirty conditions
- more active at low pH
- poor activity against pseudomonas
- high Q10 value hence increase temp increase activity
Alcohols
- cell wall damage, alter cell integrity
- require water
- mycobactericidal
- virucidal
- non sporicidal
- no dirt penetration
- volatile
Aldehyde
Cell wall damage, alter cell membrane permeability
cross-linking of cellular proteins, alter DNA structure
sporicidal
stability and toxicity issues
Quaternary Ammonium Compound
Cell wall damage, alter cell membrane permeability
- disruption of phospholipid bilayer
- have detergent properties
- active under alkali, neutral conditions
- incompatible with anionic agents
- active against gram positive
Chlorhexidine
Cell wall damage, alter cell membrane permeability
Protein coagulation
Enzyme inhibition and denaturation
- topical
- incompatible with anions –> precipitate
- gram negative less sensitive than gram positive
- inactivated by dirt, blood, organic matters
Halogens
Cell wall damage, alter cell membrane permeability
Enzyme inhibition and denaturation
inihibit DNA synthesis, replication and strand breakage
Oxidative destruction
Chlorine
- broad spectrum
- corrosive
- toxic, stability
Iodine
- stain, broad spectrum, not inactivated by organic matter
Peroxides
Enzyme inhibition and denaturation
DNA synthesis, replication and strand breakage
Oxidative destruction
- Rapidly decomposed by alkali and metals
- avoid contact with skin and eyes, rinse thoroughly
- avoid contact with consumables
Mercurials
Enzyme inhibition and denaturation
- bacteriostatic, fungistatic
- preservatives for eye drops and injections
