Lecture 5: Flashcards
Chemical Control Methods
what are 3 chemical control methods
disinfectants, antiseptics, preservatives
disinfectants
are chemicals that are capable of killing microorganisms.
CANNOT BE APPLIED TO TISSUES
antiseptics
are chemical agents that kill or inhibit growth of microorganisms and are sufficiently NON-TOXIC to be applied to living tissues.
preservatives
are included in pharmaceutical preparations or foods to prevent microbial spoilage of the product
what are chemical control methods for
- antisepsis of skin
- disinfection of equipment which cannot be sterilised by other methods
- cleaning up spills of cultures or infected clinical material
- disinfection of surfaces
- as preservatives
4 conditions influencing the effectiveness of antimicrobial agents
1: populations size (eg if 90% of pop is killed in the first minute then 90% of what remained will be killed in the next minute)
- starting pop is smaller = rate of death is quicker
2: properties of chemical agent
- dilution (eg ethanol activity is better at 70% conc.)
- pH
3 type of microbe
- phase of growth (exponential is best - takes up from environment)
- polymer , capsule or lipid production
- altered cell wall or membrane or modifies sensitive sites
- cellular aggregations/biofilms
- resistant structures (endorspores)
4: environment factors
- neutralisation by organic material
- temperature (strongly effects disinfectant - work slightly better at higher temp)
5: toxicity of agents
- bit of balance
12 factors of an ideal chemical control agent
- high antimicrobial activity
- broad spectrum of antimicrobial activity
- stability (staying potent)
- homogeneity (dont want to settle)
- adequate solubility
- minimum toxicity (to living things)
- detergent activity
- minimum material effects
- minimum inactivation by organic material
- activity at ordinary temps
- deodorising ability
- low cost
alcohol
A: non-toxic
D: endospores not killed, penetration
Major use: skin swab prior to injection
mode of action: denatures proteins and membranes (disrupting lipids in membrane - cell membrane/wall often the target)
enhanced by water
aldehydes
A: kills endospores and vegetative states
D: toxic
Major use: preserving tissues
Mode of Action: Inactivates enzymes by adding alkyl group (attach a small group of alkyl group to the proteins - inactivates and kills cell - highly active)
quaternary ammonium compounds
A: non-irritant, detergent actions
D: endospores not kill, inactivated by organic matter
Major use: Soaps, detergent, skin antispetic
Mode of action:
Physical removal, disrupts membranes (polarized side chain)
halogens and hydrogen peroxide
A: wide activity
D: inactivated by organic matter, short life
Major Use: Water chlorination, skin antiseptic
Mode of Action: Oxidises vital biochemicals (works in the same way as oxidising function enzymes and essential functional groups)
heavy metals
no advantages
D: toxic
Major use: Drops in eyes of newborn, silver dressings
Mode of Actions: Reacts with sulphydral groups
phenols and phenolic derivatives
A: wide spectrum of activity
D: Endospores not killed, some toxic, skin irritant
Major Use: Home and hospital use, mouthwashes
Mode of Actions: Denatures proteins, disrupts membranes
sterilising gases
A: kills endospores
D: Explosive and toxic to humans
Major use: Pre-wrapped disposable items
Mode of Action: Strong alkylating agent
