Control of Micro Organisms (test 2) Flashcards
Purpose of microorganism control.
PREVENT INFECTION diseases in humans, animals, & plants
- PRESERVE food & meds
- PREVENT CONTAMINATION of pure culture research
Types of microbial control.
physical
chemical
chemothereapeutic
Words ending in -cide or -cidal.
kills them all (remove the agent: no growth)
Words ending in -stasis or -static.
stops growth (bacteria is still there) -if you remove the agent it will grow back
Sterilization.
destruction of ALL forms of life (includes bacterial spores)
Disinfection.
destruction of PATHOGENS (on objects disinfectant and on ppl antiseptic
Seps.
putrid or rotten
Aseptic.
condition free of contaminating microbes
Septic.
condition with microbial contamination.
Sanitize
reduction of microbial population on and in an object (ex. milk)
Degerm.
removal of microbes from surfaces (sterilized surfaces, typically used industrially)
Factors that determine effectiveness of antimicrobial measures.
- Microbial population
- Environmental factors (organic matter cane protective)
- Times exposed
- Intensity/concentration of control measure
- microbial characteristics (gram +/-)
Which is more resistant gram +ve or gram -ve?
gram -ve
What are the 5 most susceptible infectious agents?
Enveloped viruses Gm+ bacteria Non enveloped viruses Fungi Gm- bacteria
What are the 5 most resistant infectious agents?
Prions Bacterial endospores Mycobacteria Protozoa (cysts) Fungal spores
(the spore formers, etc.)
If you have have death rate of 90% deaths per min. and your starting population is 1 million, how long would you have to apply the antimicrobial to eliminate the pop. of microbes?
after one min. 100 000 after 2 min. 10 000 after 3 min. 1000 after 4 min. 100 after 5 min. 10 after 6 min 1
7 minutes to total destruction
What are the types of physical control methods?
heat filtration radiation drying cold
What is the most effective and most cost effective method of sterilization and disinfection?
heat
Thermal death time.
TIME required to kill a pop’n of microbes at a GIVEN TEMPERATURE
Thermal death point.
TEMPERATURE required to kill a pop’n of microbes in a GIVEN TIME
How does heat kill?
- Destruction of membranes
- Denaturation (and oxidization) of proteins
- Dehydration
How does oxidation effect heats ability to kill?
speeds up reactions; oxygen attaches to different things and destroys different components of the cells
What are the 2 types of heat?
moist and dry
What advantages are there to the use of moist heat?
CONDUCTS HEAT (better penetration of material) Requires LOWER TEMPERATURES
Types of moist heat.
BOILING
PATUREARIZATION
PRESSURIZED STEAM
Boiling.
(kills most in 10-15min; fungal spores and hepA 30 min; bacterial spores 2+ hours)
What is the preferred method of sterilization?
autoclave
What is the pressure that the steam interest the autoclave at?
15psi above atmospheric
What is atmospheric pressure?
15psi
What does psi stand for?
pounds per square inch
What type of things is the autoclave used for?
bedding, utensils, instruments, saline, sol’n
Types of dry heat?
Incineration (direct flame)
Hot air baking
Incineration.
direct flame that is effective in sterilizing
- used on lab utensils (inoculation loop)
- disposal of contaminated objects (gowns, gloves, masks, plastics)
Hot air baking.
- can be used to sterilize
- 160°C for 2 hours kills spores
- used for dry powders, glassware
Filtration.
- physical removal of microbes from liquids or gases (uses a membrane filter)
- used on heat sensitive materials
- degree of removal depends on pore size
What is often needed for filtration?
vacuum to push liquid through the membrane filter
What is filtration often used on?
heat-sensitive materials
like antiserums, and antibiotics
What is the degree of removal during filtration dependent on?
power size
0.45µm, 0.22µm, 0.02µm
What type of filters are used for atmospheric air filtration?
-laminar flow hood
-face mask
HEPA filter
What does HEPA stand for?
high efficiency particulate air
What is the maximum size to be considered it HEPA filter?
Less than 0.5 micrometers
Shorter wave lengths mean…
higher energy
What types of radiation are considered high energy?
Ultraviolet and below is considered high energy
An ion is a…
charged particle
Non-ionizing radiation.
- Primarily UV
- Germicidal for air and object surfaces
- Destroys genetic material
- Poor penetration power
- Special light fixtures in industry, hospitals
- Damaging to tissues and eyes
Ionizing radiation.
- Gamma rays, x-rays
- Good penetration power
- Germicidal by destruction of genetic material
- High energy, very low wavelength
What is ionizing radiation used for?
sterilizing things that can’t be treated with high heat
(foods, drugs (vitamins), vaccines, plastics, sutures
What types of food may be currently irradiated in Canada?
Potatoes Onions Wheat Flour Spices*
What foods are being considered for irradiation?
Meats (1998-Aug2009)
What are the negatives of irradiation?
Generation of O2 free radicals
Destruction of vitamins (A, E, K)
What are some methods of preserving?
- Salting or sweetening
- Drying
- Cold
- Freeze drying
How does salting preserve?
BACTERIOSTATIC
- osmotic pressure shrivels microbes (removes water from around microbe)
- used as a preservative in foods
What is salt used to preserve?
food
How does cold preserve?
BACTERIOSTATIC
- Refrigeration slows growth (5oC)
- Freezing (-5 to -20oC) water crystals may kill some bacteria from inside the bacteria
- Deep freezing (-60 to -80oC)
- Snap Freezing -200oC smaller crystals, high preservation (doesn’t damage the cell membrane as much)
Refrigeration temp.
5 degrees
Freezing temp.
-5 to -20 degrees
Deep Freezing temp.
-60 to -80 degrees
Snap Freezing temp.
-200 degrees
Benefits of snap freezing.
smaller crystals so id doesn’t damage membranes of cells as much
What method has the highest preservation.
snap freezing
Freeze-drying.
LYOPHILIZATION
- freezing causes water crystals, which can be removed under vacuum (sublimation)
- long-term preservation
- astronaut food, lab chemicals, better transport of vaccines.
What type of preservation is more long term?
freeze drying (physical method)