Disinfection Flashcards
UV light for decontaminating. What wavelength?
254 nm
Abbreviation SAL regarding disinfection
Sterility Assurance Level
Decontamination is defined by CDC as:
Reduces the level of microbial contamination so that infection transmission is eliminated.
The amount of paraformaldehyde flakes that is typically used to generate the required amount of formaldehyde gas for area or BSC decontamination is:
0.3 g/cu. ft.
The microorganism that is considered least resistant to inactivation by chemical or physical means would be:
Lipid or medium sized viruses
According to Spaulding’s classification of device surfaces, semi-critical medical devices come into contact with mucous membranes and require what level of disinfection prior to reuse?
High
The generally accepted level for an SAL is:
1: 1,000,000
An Fo is the equivalent exposure time at what temperature?
121 degrees C
Which level of chlorine is considered appropriate by CDC and WHO for most intermediate level disinfection?
500-1000 ppm
When choosing a uv meter for measuring uv light used for disinfection, it is most important that:
a. It is battery operated
b. Gives readings in microwatts/cm2 with peak response at 254 nm
c. Deducts background radiation level
d. Is hand held
e. Gives readings in microwatts/cm2 with peak response at 298 nm
b. Gives readings in microwatts/cm2 with peak response at 254 nm
Which organism is used as a biological indicator to test gamma radiation sterilization processes?
a. Geobacillus stearothermophilus
b. Bacillus megaterium
c. Bacillus pumulis
d. Bacillus radiothermans
e. Bacillus atrophaeus
c. Bacillus pumulis
Sterilization is described as the elimination of all viable microorganism; disinfection generally refers to:
a. The elimination of all pathogens
b. The elimination of bacteria and Mycobacterium tuberculosis
c. The reduction of organisms to an acceptable level
d. The elimination of vegetative bacteria and viruses
c. The reduction of organisms to an acceptable level
The term “D-value” used in reference to sterilization refers to:
a. The time needed to reduce the concentration of a given organism by 90%
b. The number of degrees above 121o C that is required to kill off 106 organisms
c. The number of degrees above 100 o C that is required to kill off 106 organisms
d. The time needed to reduce the concentration of a given organism by 50%
e. The level of destructiveness of an autoclave cycle as measured by thermocouples
a. The time needed to reduce the concentration of a given organism by 90%
Which of the following sterilization methods would not be effective for equipment or materials that are placed inside of a paper wrap?
a. EtO
b. Vaporized H2O2
c. Gamma sterilization
d. UV light
e. Steam autoclave
d. UV light
Which of the following disinfectants is not considered toxic?
a. Isopropyl alcohol
b. Quaternary ammonium compounds
c. Chlorine compounds
d. Hydrogen peroxide
e. Depending on the level, all of the above could be considered toxic.
e. Depending on the level, all of the above could be considered toxic.
The sterilization method of choice for a reusable piece of equipment that is basically polyethylene with pvc tubing, natural rubber gaskets, and nylon tabs, would be:
a. Steam at 121oC
b. Vaporized H2O2
c. Ethylene Oxide
d. Dry heat
c. Ethylene Oxide
Rank the following in order of their resistance to physical and chemical treatments, with 1 meaning most resistant and 7 meaning least resistant: \_\_ fungi \_\_ vegetative bacteria \_\_ lipid viruses \_\_ non-lipid viruses \_\_ bacterial spores \_\_ prions \_\_ mycobacteria
(5,6,7,4,2,1,3)
__ prions
__ bacterial spores (anthrax, clostridium)
__ mycobacteria (TB)
__ non-lipid or small viruses (polio virus, coxsackievirus, rhinovirus, HAV)
__ fungi
__ vegetative bacteria
__ lipid viruses (Herpes simplex, CMV, RSV, HBV, HCV, HIV, hantavirus, ebola virus)
Higher concentrations of an active ingredient in a disinfectant may not always relate to a higher microbicidal activity. That is known to be true about the following material:
a. chlorine bleach solution
b. ethanol
c. glutaraldehyde
d. phenol
b. ethanol
A disinfectant classified as a “hospital disinfectant” by the EPA generally falls into the following ranking system that is commonly used by CDC:
a. High level disinfectant
b. Moderate level disinfectant
c. Low level disinfectant
d. Low or moderate level disinfectant, depending on formulation
e. Moderate or high level disinfectant, depending on formulation
d. Low or moderate level disinfectant, depending on formulation
Sterilization
destroys all microbial life, including high numbers of bacterial spores
Disinfection
eliminates nearly all recognized pathogens, disease causing organisms, but generally not spores, on inanimate surfaces
Antisepsis
reduction of organisms on living
tissues
Biocide
kills type of organism or
group, e.g., tuberculocide, virucide,
sporocide, etc.
Biostat .
prevents organisms or group
from growing, e.g., bacteriostat,
fungistat, etc
Sanitizer
Reduces level of organisms
to a safe level, i.e., cleaning objects
HPV Safety issues
• Toxic but not mutagenic or
carcinogenic
• 35% liquid - skin and eye irritant
• Monitor vapor leakage with detector (e.g., Drager) tube
iodophors
- Can be aqueous, tincture (in alcohol) or iodophor (complexed with surfactant)
- Usually intermediate level disinfectant
- Can cause staining and corrosion
- Easily neutralized by organics.
Hand Sanitizers alcohol percentage
They should contain no less than 60% alcohol
in order to effective.
benzalkonium chloride sanitizers
Some benzalkonium chloride sanitizers have
been shown effective against MRSA and flu
quaternary ammonium compound
Hand sanitizer limited efficacy against:
Limited efficacy against Norwalk virus; NOT
effective against Cl. difficile
ETO Validation parameters
• Critical parameters measured: – temperature – pressure/vacuum – gas concentration – humidity – time
Gamma radiation average dose
2.5 Mrad
ETO Validation biological indicator
• Biological indicator used is Bacillus atrophaeus (B. subtilis var. niger)
Gamma radiation biological indicator
Bacillus pumilus
Gamma radiation General
- Most common for food and devices
- Good penetration
- Dosimeters used to quantify dose
Ultrasound general
– Used on a suspension of liquids
– Combined with chemicals /detergents can be used to
inactivate microorganisms, e.g.,detergent and sonication will inactivate retroviruses
Chlorine Dioxide Gas condition of use
- Concentration of 10 mg/L
- Contact time of 1-2 hours
- High humidity optimal
Chlorine Dioxide biological indicator
Bacillus atrophaeus
Chlorine Dioxide • Advantages
– No harmful emissions (gas neutralized by sodium bisulfite)
– No residues
-broken down by light
-doesn’t form byproducts like bleach
Chlorine Dioxide Disadvantages
– Incompatible with uncoated
ferrous metals and latex rubbers
– Toxic – PEL of 0.1 ppm (0.3 mg/M3), STEL of 0.3 ppm
– Compatibility issues with electronics? (USEPA, Porton
Down studies)
CDC Classification of Disinfectants
• High –
can kill spores with long contact time.
Used for critical and semi-critical medical
devices.
Aka “sporocide/sterilant”
CDC Classification of Disinfectants
• Intermediate –
kills all bacteria (including
mycobacteria) except spores, fungi and
inactivates most viruses. Used for noncritical/
environmental surfaces (OK for BBP).
Aka “tuberculocidal hospital disinfectant”
CDC Classification of Disinfectants
• Low –
kills vegetative bacteria, some viruses and
fungi. Used for non-critical devices/ surfaces.
Aka “hospital disinfectant/sanitizer”
Dry Heat Sterilizers
• Cycle parameters:
– 170 C - 1 hour
– 160 C- 2 hours
– 140 C - 3 hours
– 121 C - overnight
Dry Heat Sterilizers
When are they used
• Used for materials that are damaged by
steam, cannot be penetrated by steam or
gases, or must be endotoxin free
Dry Heat Sterilizers indicator organism
• Bacillus atrophaeus is indicator organism
Ethylene Oxide Sterilizers
Primary use
for heat / radiation sensitive dry medical supplies
Ethylene Oxide Sterilizers
hazards
• Carcinogenic and an eye irritant
• Mixtures with freon and CO2 are not
explosive; pure ethylene oxide is!
Ethylene Oxide Sterilizers
conditions of use
• Absorbs to materials and must be degassed after exposure • Generally use 500-1000 mg/liter at 49-50 C with a pre-humidification cycle
Peracetic Acid
concentration for use
– Sporocidal – at levels down to 100 ppm
2500 ppm kills B.anthracis in 30 mins
Peracetic Acid
what used on and when?
– Used for food processing equipment
and some medical devices b/c non toxic residuals
– Effective at low temperature and in presence of organics
Viral Resistance
– Sensitivity based on lipoprotein coat (Klein-Deforest
scheme)
• Low - Lipid viruses
List examples
HIV, HBV, RSV, Herpes
Viral Resistance
– Sensitivity based on lipoprotein coat (Klein-Deforest
scheme)
• Moderate- Non-lipid, hydrophilic
List examples
Polio, rhino,
coxsackie, HAV
Viral Resistance
– Sensitivity based on lipoprotein coat (Klein-Deforest
scheme)
• High - Non-lipid, small
List examples
Adenovirus, rota, parvo
Viruses with high protein (serum or mucin) load and disinfection
Can make certain lipophilic viruses, e.g., influenza, as difficult to kill as nonenveloped viruses!
D-Value – Decimal Reduction Time
Time required to kill 90% of organisms or achieve 1 log10 reduction under set conditions
Formaldehyde BI
Bacillus atrophaeus is the BI
paraformaldehyde flakes for decon
Concentration in PPM by volume and % concentration by weight
10,000 ppm by volume and about 0.8%
concentration by weight
Formaldehyde gas decon temp and RH conditions
• Temperature of at least 70oF or 20oC
• Relative humidity of >70% - efficacy depends
on RH
Can polymerize in the presence of moisture
How neutralize formaldehyde decon?
• Neutralized with 110-120% of ammonium
carbonate
Hydrogen Peroxide Vapor
indicator
G. stearothermophilus
Dry Fogs
chemicals used
• Using peracetic acid (peroxyacetic
acid) or similar compounds
• Generate ultra fine atomization of
droplets less that 10 u
Dry Fogs
Biological indicators
Bacillus stearothermophilus spores
Dry fogs
Advantages
- Starting material is less hazardous and by products are acetic acid and water
- Does not seem to adversely effect electronics
- Relatively tolerant of high soil loads
- Fairly quick and cost effective
Uses for Dry Fog
- To control mold contamination in sick buildings
- Surface decontamination in pharmaceutical/ medical device cleanrooms, hospital areas, containment labs, etc.
- Odor reduction in animal facilities, locker rooms, etc.
Incinerator dual chamber paramaters
• Dual Chamber Operation parameters:
– Primary chamber: 1400F-1800F (760C-982C)
– Secondary chamber: >2000F (1093C)
Incinerator percentage volume of waste reduction
85-95%
Formaldehyde safety issues
- Toxic substance and carcinogen: eye irritant.
- Reactive with HCl / chlorine compounds
- Employee exposure limits are low
Formaldehyde safety issues
OSHA 15 minutes STEL
2 ppm
Formaldehyde safety issues
8 hour TWA
0.75 ppm
Formaldehyde safety issues
NIOSH IDLH
20 ppm
Peroxygens
hydrogen peroxide/peracetic
acid
NaOH concentration effective against viruses
1-2%
NaOH concentration effective against prions
1-2 N for 1 hour
Which is the preferred method for treatment of animal
bedding? What else is that best for?
Incineration
Also good for carcasses and pathological waste
not good for plastics
• Why is alcohol not generally acceptable for use for
bloodborne pathogen contamination?
low level and no residual
• Which chemicals are used to decontaminate prion
contaminated surfaces?
– 2 % sodium hypochlorite for 1 hour
– 2 N NaOH for 1 hour
– Environ LpH
• Chlorine bleach solutions degrade quickly because
of tap water impurities and should be prepared daily.
True or False?
True
• How many ppms of chlorine should be used for
routine lab disinfection?
• 500-1,000 ppm are appropriate for most
intermediate level disinfection
• 5,000 ppm is used for spill clean-up,
heavily soiled areas, liquid wastes
• Peracetic acid is sporocidal. What are some of it’s
benefits over other disinfectants.
• Starting material is less hazardous and by products are acetic acid and water • Doe not seem to adversely effect electronics • Relatively tolerant of high soil loads
• How many ppms of chlorine should be used for
prion
decontamination?
• 20,000 ppm is recommended for prion
decontamination
• How many ppms of chlorine should be used for spill clean-up,
heavily soiled areas, liquid wastes
• 5,000 ppm is used for spill clean-up,
heavily soiled areas, liquid wastes
• How many ppms of chlorine should be used to remove bacterial
films
• 50,000 ppm is used to remove bacterial
films
