33 - Sterilization and Disinfection Flashcards
how does microbial death occur?
exponentially, not all at once
what will help the probability of a microbial kill?
increase concentration (number of “bullets” used/unit time) and decrease in number of targets still alive
T/F the last 9 microbes will die faster than the first 900,000
FALSE, it takes just as long to kill the last 9 as the first 900,00! the more you start with, the harder it is to kill them all
what term:
removing or killing all viable forms of organisms, even bacterial spores
sterilization
what term:
eliminating most organisms, usually from surfaces (with varying levels)
disinfection
what term:
reduction of harmful microbes on animal or plant tissues
antisepsis
sterilizing agents must be _____________
microbicidal
how does microbistatic affect microorganisms
prevent growth; growth can continue when agent is removed
which items must be sterilized
critical items: items that penetrate sterile tissues (e.g. surgical instruments, implants, I.V. catheters)
which items need at least high-level disinfectant
semicritical items: contact mucous membranes or nonintact skin (e.g. endoscopes, endotracheal tubes, cystoscopes)
which items must be wiped with intermediate-level disinfectant
clinical contact items: contaminated during pt care (e.g. light handles, switches, x-ray equipment, drawer handles, pens, etc)
which items mus be cleaned with EPA-registered detergent and water
housekeeping items (e.g. floors, walls, sinks)
how does the physiological state of the organism affect susceptibility?
actively growing org. or cultures more susceptible than older stagnant ones
what properties of the organism’s environment will affect the susceptibility?
temp, pH, viscosity of solutions, and presence of organic materials
T/F boiling is not good as it doesn’t kill spores
true
what is standard autoclave conditions
121 degrees C, 15 psi, for 15 min (“important to know standard autoclaving procedure”)
how long does a dry heat oven take? what temp does it need?
1-16 hrs, needs higher temp (up to 171 degrees C)
T/F low temperatures are usually good as they are microbicidal
False, low temp is usually microbistatic
how does ultraviolet radiation (e.g. sunlight, UV lamps) do to microbes
induces cross-linking in nucleic acids
causes mutations
the problem: little penetrating power
ionizing radiation such as ___________ and __________ will cause a break in nucleic acids, mutations and penetrates well but can be dangerous
gamma rays, X rays
which chemical sterilization:
penetrates well, works on wrapped materials
good for heat-sensitive plastics, equipment
very toxic, can explode
requires at least 4-6 hr to work + hrs to detoxify
ethylene oxide (gas sterilization)
which chemical sterilization:
cross-link DNA (stops replication)
low cost, no special equipment
requires immersion for 6-10 hrs at room temp
carcinogenic, causes hypersensitivity
aldehydes
which chemical sterilization:
uses vaporized hydrogen peroxide
adds microwave or radio-frequency energy
produces free radicals that damage nucleic acids
no toxic byproducts
plasma gas sterilization
which alcohols are most common fro chemical disinfection
ethyl and isopropyl (use at 70-95% concentrations)
T/F ethyl and isopropyl are used to sterilize
False, won’t kill spores, some fungi, and some viruses such as norovirus
mechanism of disinfection of H2O2
oxidizing agent - inactivates proteins
damages enzymes
active form is free hydroxyl radical
high-level disinfectant when concentrated (3-6% generally)
con of disinfection with H2O2?
loses potency during long-term storage
Iodine precipitates _____________
proteins
what is iodophores used for?
wound antisepsis, preop skin conditioning, disinfect surfaces and equipment
what will phenols do during chemical disinfection?
disrupt lipid membranes
what is the chemical disinfectant in chlorhexidine?
derivative of phenol (carbolic acid)
T/F phenols will kill fungi, mycobaterium spp., many viruses, and bacterial spores
FALSE! everything true but they don’t reliably kill bacterial spores
what’s an example of what chlorine can kill
HIV, hepatitis viruses, recommended for norovirus outbreaks
__________ will disrupt membrane function
detergents
how do you monitor efficacy of sterilizers/autoclaves?
spore strips & chemical test strips
alcohol based hand sanitizers need to have >_______% alcohol
60
how long should alcohol based hand sanitizers be in contact with skin?
15-20 sec
T/F alcohol based hand sanitizers are no effective against COVID
false
