L5 Chemical control methods Flashcards
define disinfectant
chemicals that are capable of killing microorganisms. CANNOT be applied to living tissue
uses of disinfectants
applied to inanimate surfaces in labs and in discard jars and buckets
define antiseptics
chemical agents that kill or inhibit growth of microorganisms that can be applied to living tissue
uses of antiseptics
cleaning areas on skin
define preservatives
prevents microbial spoilage of a product
uses for preservatives
in pharmaceutical preparations or food
5 conditions that influence the effectiveness of antimicrobial agents
population size properties of the chemical agent type of microbe environmental factors toxicity of the agent
what % of microbes will die every minute
90% of the population at the start of the minute
in regards to population size what is the time it takes to have microbial numbers at an acceptable level dependant on
the initial population
what is another factor that cnotribute to the time taken to have microbial numbers at an acceptable level
using PPE to reduce contamination
what two properties of chemical agents influence the effectiveness of the antimicrobial agent
dilution
pH
how does dilution impact the effectiveness of an antimicrobial agent
some solutions are more effective when diluted
higher or lower than the recommended concentration can affect efficiency
how does pH impact the effectiveness of an anti-microbial agent
every chemical solution has an ideal pH at which it should be used
what is an example of a chemical that is more bactericidal when diluted with water
ethanol is more effective at 70%
at what pH is hypochlorite solution more effective
lower (acidic) pH
how does the type of microbe impact the effectiveness of an anti-microbial agent (6)
phase of growth
polymer, capsule or lipid production
altered cell wall or membrane or modified sensitive sites
cellular aggregations/biofilms
resistant structures
microbial interactions (competition, antagonism, mutualism)
how does the phase of growth impact the effectiveness of an antimicrobial agent
bacteria in the log phase will take up chemicals from the environment faster than those in stationary phase
how do polymers, capsules and lipid production impact the effectiveness of an antimicrobial agent
limits diffusion of chemicals into the cell wall
how does having an altered cell wall or membrane or modified sensitive sites impact the effectiveness of an antimicrobial agent
reduced permeability and effectiveness of disinfectants
how do cellular aggregations/biofilms impact the effectiveness of an antimicrobial agent
thick layer of bacteria so it is harder to reach the middle microbes (they are protected by the outer microbes)
how do resistant structures impact the effectiveness of an antimicrobial agent
the release of chemicals triggers cells to produce endospores that are resistant to disinfectant
how do microbial interactions impact the effectiveness of an antimicrobial agent
microbes are not found in a pure culture in the environment and these interactions impact the effectiveness
microbe of the day
mycobacterium tuberculosis
facts about mycobacterium tuberculosis
aerobic, bacillus
slow mean generation time = more resistant to disinfectant (decreased uptake of chemicals)
-waxy coating on cell surface = reduced permeability
resistant to desiccation and difficult to gram stain
most to least resistant bacteria to germicidal chemicals
endospores mycobacteria nonlipid or small viruses Funghi vegetative bacteria enveloped or medium-sized viruses
what environmental factors impact the effectiveness of disinfectants
neutralisation of organic material
temperature
what needs to be considered when looking at the toxicity of the agent
toxicity towards the cell/microbe
toxicity to the user
how many things need to be considered when finding the ideal chemical control agent
12
what are the 12 things that need to be considered for an ideal chemical contorl agent
high antimicrobial activity broad spectrum stability homogeneity adequate solubility minimum toxicity detergent activity minimum material effects minimum inactivation by organic material activity at ordinary temperatures deordiring ability low cost
7 types of chemical control agents
alcohol aldehyde quarternary ammonium compounds halogen and hydrogen peroxide heavy metals phenols and phenolic derivatives sterlising gases
advantages to alcohol
non toxic
advantages to aldehydes
kills endospores and vegetative cells
advantages to quarternary ammoinium compounds
non-irritant detergent action
advantages to halogens and hydrogen peroxide
wide activity
advantages to phenol and phenolic derivatives
wide spectrum of activity
examples of alcohols
ethanol
isopropanol
how do alcohols kill microbes
disrupting the lipids in the cell membrane and denaturing proteins
disadvantages to alcohols
does not kill endospores
poor penetration
major use of alcohol
skin swab prior to injectoin
tincture
disadvantages to aldehydes
toxic to human cells
examples of aldehydes
formaldehyde
glutaraldehyde
major use of aldehydes
preserving tissues
embalming
how do aldehydes work
inactivates enzymes by adding an alkyl group
Disadvantages to quaternary ammonium compounds
endospores not killed
inactivated by organic matter
examples of quaternary ammonium
cetylpyridinium chloride
benzalkonium chloride
major use of quaternary ammonium compounds
soaps
setergents
skin antiseptics
how do quaternary ammonium compounds work
penetrating and destroying cytoplasmic membranes
structure of quaternary ammonium compounds
long hydrocarbon chain
the charged nitrogen atom has 4 hydrophobic organic groups (quart)
disadvantages to halogens and hydrogen peroxide
inactivated by organic matter
short life
what percentage does H2O2 kill and what is it used for
3%
disinfecting medical instruments
major use of halogens/H2O2
water chlorination
skin antiseptic
how do halogens and H2O2 kill
oxidises vital biochemcials
-oxidise functonal groups
disadvantages to heavy metals
toxic
major use of heavy metals
drops in eyes of newborns at risk of ghonnerheoa
silver dressings
how do heavy metals kill microbes
react with the sulphhydral groups which poisons the enzymes
disadvantages to phenols and phenolic derivatives
endospores not killed
some toxic
skin irritant
major uses of phenols and phenolic derivatives
home
hospital use
mouth washes
how do phenols and phenolic derivatives kill
denatures protiens and disrupts membranes
structure of phenols and phenolic derivatives
benzene ring with hydroxyl group
examples of phenols and phenol derivatives
phenol
orthocresol
orthophenylphenol
hexachlorophene
advantages to sterilising gases
kills endospores
disadvantages to sterilising gases
explosive
toxic to humans
major use of sterilising gases
pre-wrapped disposable items
how do sterilising gases work
strong alkylating group
example of sterilising gas
ethylene oxide
