[1S] UNIT 1.2 Control of Microbial Growth Flashcards
TYPE OF ORGANISM
T/F: The ability of the microorganism to withstand the different disinfecting / sterilizing agents depend on the chemical composition and protective mechanisms inherent to such microorganism.
T
Are produced by some bacteria to confer resistance to heat, radiation, and other harsh environmental conditions.
Endospores
TYPE OF ORGANISM
T/F: Some bacteria form biofilms that protect them from radiation, desiccation, high pressure, extreme pH temperature, and antimicrobial agents
T
Refers to the number of microorganisms present in the specimen/object.
Microbial Load
CONCENTRATION OF THE AGENT TO BE USED
T/F: Less concentrated disinfectants are effective in microbial inhibition or killing.
F; More concentrated
PRESENCE OF ORGANIC MATERIAL
T/F: Presence of mucus, blood, and pus can inactivate the disinfecting agent by preventing the full contact of the agent and the material to be disinfected.
T
PRESENCE OF ORGANIC MATERIAL
Examples of chemical agents that can be inactivated include bleach and ______.
Quaternary Ammonium Compound (QUATS)
NATURE OF SURFACE TO BE DISINFECTED
Devised a logical approach for disinfection/sterilization of inanimate objects or surfaces based on the degree of risk involved in their use.
Earle Splaulding
NATURE OF SURFACE TO BE DISINFECTED
According to Spaulding classification, equipment/items are regarded as: _______, ___________, __________.
Critical
Semi-critical
Non-critical
NATURE OF SURFACE TO BE DISINFECTED
Are devices that enter sterile body parts, including the vascular system
Critical Items
NATURE OF SURFACE TO BE DISINFECTED
Are devices that enter sterile body parts, including the vascular system
Critical Items
NATURE OF SURFACE TO BE DISINFECTED
Are those that come in contact with non-intact skin or mucous membrane but does not penetrate them
Semi-critical Items
NATURE OF SURFACE TO BE DISINFECTED
T/F: High level of disinfection is required for the critical items, while low level of disinfection is implemented for non-critical items
T
NATURE OF SURFACE TO BE DISINFECTED
Touches only the intact skin but not the mucous membrane
Non-critical Items
Refers to the length of time a chemical agents needs to stay on a targeted surface in order to become an effective disinfectant/sterilant
Contact Time
CONTACT TIME
T/F: Applying the chemical agent and wiping it immediately may render it useless in killing or inhibiting growth microorganisms
T
TEMPERATURE & PH
T/F: Most disinfectants are effective at room temperature under a basic condition
F; acidic condition
TEMPERATURE & PH
T/F: Disinfection can be enhanced by an increase in temperature only up to a certain degree
T
TEMPERATURE & PH
T/F: Too much increase in temperature may affect the efficacy of a disinfectant and therefore strengthen its germicidal activity
F; weaken
TEMPERATURE & PH
T/F: In chlorination, as pH goes up, the concentration of hypochlorite ions decreases and disinfection becomes less effective
F; increases
COMPATIBILITY OF DISINFECTANTS
T/F: QUATS and bleach should not be used together. Mixing it may result in a creation of toxic gas
T
What are the factors affecting microbial growth?
● Type of Organism
● Microbial Load
● Concentration of Agent to be used
● Presence of Organic Material
● Nature of surface to be disinfected
● Contact time
● Temperature
● pH
● Compatibility of disinfectants
refers to methods employed to prevent entry of organisms into the body as well into test tubes, flasks or plates used in microbial cultivation
Aseptic Technique
refers to the absence of microbes in an area or object
Asepsis
a condition in which microbial growth and multiplication is halted or inhibited. The microorganism is not killed or destroyed in the process. Include the use of refrigeration as well as dyes.
Bacteriostasis
involves chemical disinfection of living tissues (i.e. mucus membrane, skin) as well as in the treatment of wounds. The chemical agent employed is called an _______
antiseptic / Antisepsis
T/F: In bacteriostasis, the microorganism is not killed or destroyed in the process.
T
are chemical sterilants used to destroy all
forms of life. It is also known as chemical sterilants
Biocide
microorganisms inadvertently introduced to specimens or bacterial culture
Contaminant
the process of removal of pathogenic microorganisms so materials/items are safe to handle or dispose.
Decontamination
removal of transient microorganisms from the skin using mechanical cleansing or antiseptics.
Degerming
process of destruction of pathogenic microorganisms except spores, prions and other microorganisms.
Disinfection
reduction of pathogens on eating
utensils to safe public health levels by mechanical cleansing or use of chemicals.
Sanitization
destruction of all forms of life including bacterial spores.
Sterilization
lowest temperature in which all bacteria in a liquid culture will be killed in 10 minutes 1
Thermal Death Point
minimal length of time in which all bacteria in a liquid suspension will be killed at a given temperature
Thermal Death Time
FACTORS THAT IMPACT THE EFFECTIVENESS OF DISINFECTANTS
CONSIDERATION: Some surfaces or materials may be damaged. Many medical instruments are damaged by eat or corrosive materials
Surface or material to be disinfected
FACTORS THAT IMPACT THE EFFECTIVENESS OF DISINFECTANTS
CONSIDERATION: Excess dirt, blood, mucus, or pus may inactivate the agent; it may be necessary to clean the surface prior to disinfection
Presence of organic material
FACTORS THAT IMPACT THE EFFECTIVENESS OF DISINFECTANTS
CONSIDERATION: The amount of time the disinfectant is in contact with the surface affects the amount of organism destruction. Betadine must have a contact time of ______ minutes in order to kill microorganisms
1 to 2
FACTORS THAT IMPACT THE EFFECTIVENESS OF DISINFECTANTS
CONSIDERATION: Different type of microorganism may be more resistant to the effects of certain disinfectants. Spores, mycobacteria, prions, and biofilms may require specific agents
Organism Type
● Most commonly used method
● Cheap, economical and reliable
● It could either be through MOIST HEAT or DRY HEAT
Heat
FACTORS THAT IMPACT THE EFFECTIVENESS OF DISINFECTANTS
CONSIDERATION: The amount and concentration of disinfectant required to adequately destory microorganism vary by product. Manufacturer instructions regarding preparation and use should always be followed.
Concentration of disinfectant
FACTORS THAT IMPACT THE EFFECTIVENESS OF DISINFECTANTS
CONSIDERATION: The presence of greater amounts of microorganism usually requires greater contact time with the disinfectant
Amount of organism present
FACTORS THAT IMPACT THE EFFECTIVENESS OF DISINFECTANTS
CONSIDERATION: Temperature and pH can alter activity. Most disinfectant require increased contact time in colder temperatures. The pH of the material to be disinfected must be considered, as some disinfectants are only active within a certain range.
Temperature and pH
2 Sterilization Methods
● Physical Means
● Chemical Means
Principle of dry heat
Oxidation
Longer Exposure time and higher temperatures
Dry Heat
For the sterilization of inoculating loops, needles, mouth of tubes
Open Flame
DRY HEAT
● HOT AIR OVEN:
● TEMPT REQUIREMENTS:
Sterilize Glasswares
160-180C for 1.5-3 hours
OPEN FLAME
BUNSEN BURNER:
Flame Sterilization
● For disposal of hospital waste (infectious)
● Now Outlawed: RA 8749 Clean Air Act of 1999
Incineration
T/F: In moist heat, all microorganisms are killed except prions
T
● Or HEAT UNDER STEAM PRESSURE
● More effective than dry heat
● Shorter time of exposure
● Sterilization method of choice for heat stable objects
Moist Heat
MOIST HEAT
PRINCIPLE:
AUTOCLAVE:
Coagulation of Proteins
121C, 15psi (1atm) for 15 minutes
● Form of disinfection; DOESN’T KILL SPORES
● 100C for 10-15 minutes
Boiling
eliminates food borne pathogens responsible for food spoilage
Pasteurization
PASTEURIZATION METHODS
1. Batch Method:
2. Flash Method
3. High Tempt Short Time
- 63C for 30minutes
- 72C for 15seconds
- 72C-140C then 72C for <5sec
● Flowing Steam
● Fractional
● Intermittent
● 100C for 30 mins for 3 days
● Arnold’s Sterilizer
Tyndallization
● for sterilization of high protein media
● 75-80C for 2hrs on 3 consecutive days
Inspissation
TYPE OF MOIST HEAT: Steam Under Pressure
APPARATUS EMPLOYED: Gravity Displacement
TEMPERATURE: 121C @ 15psi (1 atm)
TIME: 15-20 minutes
APPLICATION: ?
Sterilization of Culture Media
TYPE OF MOIST HEAT: Steam Under Pressure
APPARATUS EMPLOYED: Gravity Displacement
TEMPERATURE: 121C @ 15psi (1 atm)
TIME: ?
APPLICATION: Biological waste in broth or solid media
30 minutes
TYPE OF MOIST HEAT: Steam Under Pressure
APPARATUS EMPLOYED: Vacuum Autoclave
TEMPERATURE: 132 @ 15psi (1 atm)
TIME: ?
APPLICATION: Biological waste in broth or solid media
4 minutes
TYPE OF MOIST HEAT: Steam Under Pressure
APPARATUS EMPLOYED: Vacuum Autoclave
TEMPERATURE: 132 @ 15psi (1 atm)
TIME: 30-60 minutes
APPLICATION: ?
Biologic waste (blood/body fluids)
TYPE OF MOIST HEAT: ?
APPARATUS EMPLOYED: Arnold’s Sterilizer
TEMP: 100C
TIME: 30 mins for 3 consecutive days with incubation period in between sterilization
APPLICATION: Heat sensitive media that cannot withstand autoclave temperature
Tyndallization
TYPE OF MOIST HEAT: ?
APPARATUS EMPLOYED: Inspissator
TEMP: 75-80C
TIME: 2 hours for 3 successive days
APPLICATION: High protein media
Inspissation
TYPE OF DRY HEAT: Incineration
APPARATUS EMPLOYED: ?
TEMP: 870-980C
TIME: -
APPLICATION: Safest method to destroy all microorganisms including prions; applicable for disposal of carcasses and medical wastes
Incinerator
TYPE OF DRY HEAT: ?
APPARATUS EMPLOYED: Dry heat oven
TEMP: 160-180C / 121C
TIME: 1.5-3 hrs / 16 hrs
APPLICATION: For glassware, oils, petroleum, powder
Hot Air Sterilization
TYPE OF DRY HEAT: ?
APPARATUS EMPLOYED: Bunsen burner or alcohol lamp / Bacti-cinerator sterilizer
TEMP: - / approx. 815.6C
TIME: until red hot (for loop & needle)
APPLICATION: Sterilization of inoculation needle, loops, tips of metal forceps
Direct Flaming
Separation of bacteria from liquids or air
Filtration
FILTRATION OF LIQUIDS: through Berkefeld
diatomaceous earth
FILTRATION OF LIQUIDS: through
○ Morton: _____ ______
○ Seitz: ______ ____
sintered glass
asbestos pad
FILTRATION OF LIQUIDS: through
○ Chamberland-Pasteur: ______ _____
○ Membrane Filters: ________ _____
unglazed porcelain
Cellulose esters
For critical sterilization: ______ filter must be used
0.22um
FILTRATION OF AIR through: ?
○ able to remove organisms >0.3um
○ Uses: Laboratory hoods, rooms of
immunodeficient patients
HEPA (High Efficiency Particulate Air Filters)
MOA: alkylation of Nucleic acid
Radiation
● Gamma rays or electron beams
● Short wavelength but high energy
● USE: Sterilization of disposable materials in the medical industry
Ionizing Radiation
● UV rays
● Long wavelength but low energy
● Poor penetration
● USE: disinfection of surfaces
Non-ionizing
PHYSICAL METHODS
● dehydration
● removal of water to stop metabolic action of bacteria
Dessication
PHYSICAL METHODS
○ through PLASMOLYSIS
○ high concentrations of sugar/salt
High Osmotic Pressure
PHYSICAL METHODS
○ bacteriostatic
Exposure to Low Temperature
CHEMICAL METHODS
○ cold sterilization
○ gas chamber (450-700 mg/L), 55-60C
○ minimum time: 2hours
○ Principle: Alkylation of nucleic acids
GASEOUS CHEMICALS: ETHYLENE OXIDE
CHEMICAL METHODS
○ shorter contact time of killing
GASEOUS CHEMICALS: Hydrogen Peroxide and Periacetic Acid
CHEMICAL METHODS
○ Mode of Action: Protein Denaturation and Lipid Dissolution
○ 70% ETHANOL
Alcohols
CHEMICAL METHODS
Mode of Action: Alkylation of Nucleic Acids and Protein Denaturation
■ 2% GLUTARALDEHYDE: disinfectant
■ 40% FORMALIN
Aldehydes
CHEMICAL METHODS
○ Mode of Action: Cytoplasmic Membrane Destruction
○ Uses: Commonly used antiseptic in surgery
Chlorhexidine
CHEMICAL METHODS
● Mode of Action: Oxidation of cellular Components and Protein Denaturation
● Iodine
Halogens
HALOGENS
alcohol and iodine solutions for antiseptics
Tincture
HALOGENS
● iodine plus a neutral polymer carrier
● must be diluted
● Preferrable
● ex. POVIDONE-IODINE (“BETADINE”)
Iodophors
HALOGENS
■ one of the oldest and common disinfectants
■ In the form of : HYPOCHLORITE
● not used as sterilants
■ Dilution: 1:10 dilution of 5.25%
Chlorine
CHEMICAL METHODS: WATER STERILIZATION
Bleach:Water
2-3 drops bleach in 1 L of water for 30 minutes
CHEMICAL METHODS: WATER STERILIZATION
Addition of Chlorine in swimming pools and in drinking water
Copper Sulfate Pentahydrate
CHEMICAL METHODS: WATER STERILIZATION
Collection for Water Testing
Add Sodium Thiosulfate
CHEMICAL METHODS
○ Rarely used, bacteriostatic
○ Mode of Action: protein and enzyme inactivation
Heavy Metals
CHEMICAL METHODS: HEAVY METALS
■ Mercury: ?
■ Silver: ? (Crede’s Prophylaxis)
■ Copper: ? – anti-algae
Merthiolate
1% Silver Nitrate
Copper Sulfate
CHEMICAL METHODS
Mode of Action: oxidation of cellular components
■ Hydrogen peroxide
■ Ozone
Oxidizing Agents
CHEMICAL METHODS
○ Mode of Action: Protein denaturation, cell
membrane andenzyme inactivation
○ Chemically substituted phenol compounds
○ Less toxic and more effective
■ Examples: ortho-phenylphenol and ortho-benzyl-para-chlorophenol
■ Uses: Hospital and institutional disinfection
Phenolic Compounds
CHEMICAL METHODS
○ Mode of Action: Protein denaturation, cell
membrane andenzyme inactivation
○ Chemically substituted phenol compounds
○ Less toxic and more effective
■ Examples: ortho-phenylphenol and ortho-benzyl-para-chlorophenol
■ Uses: Hospital and institutional disinfection
Phenolic Compounds
CHEMICAL METHODS
Mode of Action: interruption of electron
transport, enzyme inhibition and membrane destruction
Hexachlorophene
CHEMICAL METHODS
○ Effective against Gr (+)
○ Residual effect
○ TOXIC
Hexachlorophene
CHEMICAL METHODS
○ Mode of Action: cell wall disruption and enzyme inactivation
○ Effective against Gr (+)
○ Not affected by organic compunds
Chloroxylenol
● Mode of Action: protein denaturation and cell
membrane destruction
● surface active agents; reduce surface tension
● inactivated by organic compounds and hard water (ex. Benzalkonium Cl (Zephiran), Cetylperidium Chloride)
○ Resistant to M. tuberculosis
QUATS
● Mechanical Action by rubbing and scrubbing
○ Possess antibacterial ingredients such as triclocarbon or triclosan
Soaps & Detergents
How to check the effectiveness of physical methods?
Through the use of spore strips & determination of phenol coefficient
EFFECTIVENESS OF PHYSICAL METHODS
Bacillus subtilis var. niger
HOT-AIR OVEN
EFFECTIVENESS OF PHYSICAL METHODS
Bacillus subtilis var. globigii
Ethylene Gas
EFFECTIVENESS OF PHYSICAL METHODS
Bacillus pumilus
Ionizing Radiation
EFFECTIVENESS OF PHYSICAL METHODS
Bacillus stearothermophilus
Autoclave