Disinfectants and antiseptics Flashcards
Define disinfection
The process of removing micro-organisms from surfaces of inanimate objects does not necessarily kill all the organisms
What are the 3 classes of disinfectants?
High level, intermediate level, low level
What are the ideal properties of disinfectants?
broad spectrum
rapid kill (5 mins)
must not damage material to be disinfected
easy to prepare and use
stable, last for a long time
inexpensive - due to size of areas needing cleaning
Define antisepsis
The destruction or inhibition of micro-organisms on living tissues
Purpose of antiseptics
Decrease the incidence of wound infections
Decrease HAI
Decreased normal skin flora prior to surgery - pre-op surgical scrubs, patient pre-op skin preps
decreased spread of infection by hand cleansing
Name the two populations of bacteria on our skin
Transient bacteria - gram-negative example, E. coli - can pick up from surfaces
Resident bacteria - gram positive example, Staphylococcus aureus, staphylococcus epidermidis
What are the ideal properties of antiseptics
Adequate spectrum anti-microbial activity
Immediate activity (active within 1 min)
Persistent activity - how long activity is retained
Cumulative (residual) activity - antimicrobial effects when used
non-toxic, non-irritant
cost
motivation to use
What factors affect choice of chemical agent?
Intended application
number and type of micro-organisms present
environmental factors
safety, stability, cost, easy to use
properties of chemical agent
What is the most resistant and least resistant micro-organism?
Prions (most resistant)
Lipid enveloped viruses (HIV, HBV)
Describe the environmental factors which affect the choice of the chemical agent
ORGANIC MATTER - blood, pus, food residues and dirt can decrease antimicrobial activity - can attach to the bacteria making it hard to clean
DIVALENT CATIONS (Ca2+, Mg2+) - decreased activity, stabilise bacterial cell wall, block disinfectant absorption sites
Define dilution coefficient
A number that expresses the effectiveness of a disinfectant for a given organism
The higher the dilution coefficient the more affected the chemical is by dilution
How is pH affected
affects survival growth and growth or organism
affects potency, dependent on chemical :
- ionisation
- polymerisation
- consider concentration
Describe the evaluation criteria for liquid disinfectants
Use a range of microbial types
standardised cell number
given temperature and time interval
based on ability to kill microorganisms (not inhibit them)
parallel conditions under which disinfectants is being used
What is the suspension test?
Dilutions of disinfectant added to standardised bacterial suspension in water and albumin - incubate at a specific temperature
- at specific time intervals - e.g. at 5 mins, see how many have survived.
- remove sample
- neutralised disinfectant
- determine viable count
- calculate concentration
What type of test is the suspension test?
Quantitative test
test for efficacy of disinfectants and antiseptics
give us the concentration for each type of bacteria tested
