Ch 9: Microbial Control Flashcards
Why are Prions resistant to elimination?
Prions are simple; no genes; protein is already misfolded
Why are Endospores resistant to elimination?
Endospores have an extremely tough spore coat
Why are Mycobacterium resistant to elimination?
Mycobacterium has a waxy cell wall
What are the levels of decontamination?
- Sterilization
2a. Disinfection
2b. Antisepsis
3a. Sanitization
3b. Degermation
What is sterilization?
destruction or removal of ALL viable microbes including endospores and viruses from inanimate objects
Using an autoclave on Surgical/dental instruments is an example of what kind of decontamination?
sterilization
What is disinfection?
destruction or removal of vegetative pathogens but not endospores (can also remove toxins) from inanimate objects/surfaces
What kind of decontamination would wiping a countertop down w/ bleach be?
disinfection
What is antisepsis?
destruction or inhibition of vegetative pathogens but not endospores from living tissues (skin & mucous membranes)
What kind of decontamination would wiping your skin w/ an alcohol wipe (prior to needle injection) be?
Antisepsis
What is sanitization?
reduction in the number of microorganisms to acceptable levels on inanimate objects/surfaces
When dishes are washed with soap/detergent and warm/hot water in a restaurant, what kind of decontamination would this be?
sanitization
What is degermination?
reduction in the number of microorganisms on living tissues (human skin)
What kind of decontamination is washing hands after you have been in contact with fomites in public places and before you touch your eyes, nose or mouth?
degermination
To reduce the number of foodborne microbes to acceptable levels on utensils in a restaurant, they are placed in the dishwasher. What level of decontamination is this?
sanitization
Which list of microbes is correctly ordered from most resistant to decontamination to least resistant?
A) Bacterial endospore, protozoan cyst, enveloped virus
B) Protozoan cyst, enveloped virus, bacterial endospore
C) Bacterial endospore, enveloped virus, protozoan cyst
D) Enveloped virus, protozoan cyst, bacterial endospore
E) Protozoan cyst, bacterial endospore, enveloped virus
A) Bacterial endospore, protozoan cyst, enveloped virus
What are the types of heat used to control microbes?
Dry and Moist Heat
What is moist heat?
Moist heat is used to denature and/or coagulate microbial proteins
- Inactivates enzymes; disrupts structure
What is dry heat?
Dry heat is used to dehydration cells, denature proteins, and oxidize (burn to ashes) biological molecules
- complete destruction of microbes
Why is an endospore tough to kill?
Endospore-forming bacteria are difficult to kill because of their tough spore coat and metabolic inactivity
What are two endospore forming bacteria and when are they resistant/weak to decontamination?
Bacillus & Clostridium
- In the endospore state they are thermoduric (resistant
to heat killing)
- in vegetative state they are easily killed
What are the types of moist heat that are used to decontaminate?
Boiling Water
Steam under pressure
Tyndallization
Pasteurization
How is boiling water used to decon?
Form of moist heat decon
Decontamination achieved at 100 ˚C for 30 minutes
Kills most microbes including pathogens but not endospores
How is steam under pressure used to decon?
Form of moist heat decon
Pressure above normal atmospheric will result in steam temperatures above 100˚C
- 15 psi above normal = 121˚C
e. g. autoclave & home pressure cooker
Effectively destroys endospores
Sterilizes inanimate objects/substances
How is tyndallization used to decon?
Intermittent steam for 30-60 minutes over 3 days
- Used for heat-sensitive media or canned foods
This allows endospores to germinae after cooling, and then another cycle of steam kills vegetative cells
How is pasteurization used to decon?
disinfection of beverages at 71.6 ˚C for 15 seconds
- Ultra-pasteurization @ 134 ˚C for 1-2 seconds
- Control milk-borne pathogens
What are the types of dry heat used for decon?
hot air or flame
Hot Air: oven
- Effective at 150-180˚C for 2-4 hrs
Flame: incineration
- Flame 1870˚C
- Furnace 800-6500˚C
Why is moist heat usually better at decon that dry heat?
To achieve the same level of decontamination, temperature and time of exposure for dry heat is greater than for moist heat
How can colder temperatures be used to control microbial growth?
reduce metabolism and inhibit growth
- eg. refrigerate or freeze
What are some other options for extending shelf life of a product besides refrigeration/freezing?
dehydration to remove water
lyophilization (freeze-drying)
hypertonic environments
How does a hypertonic environment extend shelf life?
High solute (salt, sugar) concentrations will inhibit microbial growth by increasing osmotic pressure - Bacteria will undergo plasmolysis
What types of radiation can be used to decontaminate?
Ionizing and Non-ionizing radiation
What is ionizing radiation?
gamma rays (radioactive isotopes) can penetrate thru solid objects/layers and damage microbial DNA
What is a benefit of ionizing radiation?
alternative sterilization method for materials sensitive to heat or chemicals such as foods (fruits, vegetables, meats)
What is non-ionizing radiation?
ultraviolet (UV) rays cannot penetrate and only affect upper surface of objects to damage microbial DNA
How can non-ionizing radiation be used to decontaminate?
germicidal lamps are used for disinfection of inanimate surfaces, air, or water can be used to inactivate protozoan cysts but not bacterial endospores
What method can be used to physically remove microbes and endospores from fluids?
filtration
What are the types of filtration?
HEPA filters are used to purify air
Liquid filters are used to sterilize heat-sensitive liquids, such as serum, vaccines, media
What physical method of control would be most useful against airborne Bacillus anthracis endospores in an office space?
A. Incineraton B. Pasteurization C. Non-ionizing radiation D. HEPA filtration E. Tyndallization
D. HEPA filtration
An autoclave is a sterilizer that uses:
A. Dry heat B. Ionizing radiation C. High speed air flow D. Extreme cold temperatures E. Steam under pressure
E. Steam under pressure
What halogens are used to control microbial growth?
chemical methods of microbial control
halogens such as chlorine and iodine are used as disinfectants or antiseptics
How do halogens like chlorine and iodine work?
disrupt sulfhydryl groups in amino acids and inactivate microbial enzymes and metabolism
What is betadine?
Betadine is an iodine solution that is used on skin prior to catheter insertion or surgical incision
What phenolic agents are used to control microbial growth?
chlorhexidine and triclosan are phenolic agents added to soaps that disrupt cell walls and membranes and cause microbial cell lysis
What alcohols are used to control microbial growth?
ethanol and isopropanol are alcohols that are used as germicidal agents that dissolve membrane lipids, disrupt cell surface tension and denature proteins
At what concentration can alcohols be used for antisepsis?
70%
What is hydrogen peroxide?
hydrogen peroxide is an effective antiseptic and disinfectant
How does hydrogen peroxide work? What can it be used as?
forming hydroxyl free radicals with biological molecules
Can be used as:
- Skin and wound cleaner
- Quick method for disinfecting medical equipment
In August 2005, 3800 patrons at Seneca Lake Park (NY) “sprayground” came down with diarrhea, vomiting, fever, cramps. The cause was discovered to be Cryptosporidium parvum, a protozoan parasite. Inspectors confirmed that chlorination and filtration were standard procedures for treatment of the recirculated water. Why were these methods unsuccessful in eliminating this pathogen? What type of water treatment could be added to help?
These methods were unsuccessful b/c the protozoan parasite formed a cyst resistant to these methods of decon
Ionizing radiation could be used
In 2001, a letter containing a mysterious powder was delivered to the Hart Office Building in Washington, DC. It was discovered that this letter contained a deadly pathogen, Bacillus anthracis. What method of decon was used?
The office was cleared and the EPA used HEPA filtration and chlorine dioxide gas for treatment.
What was done to ensure decon worked after the anthrax letter incident?
Paper strips containing a non-pathogenic bacterium were placed throughout the office. After decontamination, the strips were collected and cultured. No bacterial growth showed the decontamination procedure worked and workers could safely return to the building.
Triclosan is a(n) ________ compound that is used as an antibacterial agent in hand soap, detergents, and toothpaste.
phenolic
Which of the following uses a halogen for microbial control?
A. Water is used to rinse off dishes in the sink
B. Isopropanol is used to control skin microbes before
needle injection
C. Surgeons scrub their hands with soap containing
chlorhexidine
D. Medical equipment can be sterilized by soaking in
hydrogen peroxide
E. A swimming pool is chlorinated to inhibit microbial
growth
E. A swimming pool is chlorinated to inhibit microbial
growth
