Week 9i Microbio Exam 3

sepsis

refers to bacterial contamination

asepsis

is the absence of significant contamination

-aseptic surgery echniques

aseptic surgery techniques

prevent the microbial contamination of wounds

sterilization

removing and destroying all microbial life

commercial sterilization

killing Clostridium botulinum endospores in canned goods

disinfection

destroying harmful microorganisms on inanimate surfaces or environments

antisepsis

destroying harmful microorganisms from living tissue

degerming

the mechanical removal of microbes from a limited area

sanitization

lowering microbial counts on eating utensils to safe levels

biocide (germicide)

treatments that kill microbes

bacteriostasis

inhibiting, NOT KILLIN, microbes

selection of disinfectant

1) must be fast-acting in the presence of organic materials

2) must be effective against all microorganisms without destroying tissue or acting as a toxin if ingested

3)easily penetrate the material to be disinfected without discoloration or damage

4) easy to prepare and stabile in the environment where it is to be used

5) inexpensive and easy to use

6) not have an unpleasant odor

is there a perfect disinfectant?

there is no perfect disinfectant that meets all criteria

patterns of microbial death are caused by

microbial control agents

example of microbial death

exponential death rate

microbial death curve

effectiveness of treatment for the rate of microbial death depends on

-number of microbes

-environment (organic matter, temperature, biofilms)

-time of exposure

-microbial characteristics (endospores, cell wall)

action of microbial control agents

-damage to plasma membrane (causes leakage of cellular contents & interferes with cell growth)

-damage to proteins (enzymes)

-damage to nucleic acids

damage to plasma membrane action of microbial control agents

causes leakage of cellular contents & interferes with cell growth

heat

denatures enzymes

-TDP

-TDT

-DRT

thermal death point TDP

lowest temperature at which all cells in a liquid culture are killed in 10 min

thermal death time TDT

minimal time for all bacteria in a liquid culture to be killed at a particular time

decimal reduction time (DRT)

minutes to kill 90% of a specific population of bacteria at given temperature

moist heat sterilozation

-moist heat coagulates/denatures proteins

-boiling

-free-flowing steam

autoclave

steam under pressure

-121 degrees C at 15 psi for 15 min

autoclave (functions)

-kills all organisms (except prions) and endospores

-steam must contact the item’s surface

-preferred method for sterilization in health care environments

moist heat autoclave

-steam to enter the steam chamber and expel air—> chamber pressure and temperature build up to the proper levels

-after the appropriate period of time, another valve opens to allow steak to escape the chamber

larger containers require (moist heat sterilization)

longer sterilization times

what is used to indicate sterility

test strips

the effect of container size on autoclave sterilization times for liquid solutions

*Sterilization times in the autoclave include the time for the contents of the containers to reach
sterilization temperatures. For smaller containers, this is only 5 minutes or less, but for a 9000-
milliliter bottle it might be as much as 70 minutes. Liquids in an autoclave boil vigorously, so
their containers usually are filled only up to 75% of capacity.

examples of sterilization indicators

heat

-pasteurization

-High-temperature short-time (HTST)

-Thermoduric

pasteurization

reduces spoilage organisms and pathogens in milk and juices

High-temperature short-time (HTST)

thermoduric

organsisms survive, (heat) but are unlikely to cause disease or to spoil refrigerated milk

ultra-high-temperature (UHT) treatments

-will sterilize milk, creamer and juice which can be stored without refrigeration

-rapidly heated to 140 degrees C for 4 seconds, then followed by rapid cooling

ultra-high-temperature (UHT) treatments process

rapidly heated to 140 degrees C for 4 seconds, then followed by rapid cooling

dry heat sterilization

kills oxidation

dry heat sterilization kills oxidation by

-flaming

-incineration

-hot-air sterilization (Oven 170 degrees C, 2 hours)

filtration

-passage of substance through a screen like material

-used for heat-sensitive materials

-high-efficiency particulate (HEPA) filters —> remove microbes > 0.3 um in diameter

-Membrane filters—> remove microbes > 0.22 um [pore sizes of as small as > 0.05um are available which can filter out viruses and large proteins]

high-efficiency particulate (HEPA) filters

remove microbes > 0.3 um in diameter

Membrane filters

remove microbes > 0.22 um [pore sizes of as small as > 0.05um are available which can filter out viruses and large proteins]

pore sizes of as small as > 0.05um

are available which can filter out viruses and large proteins

physical methods of microbial control

-low temperature

-high pressure

-desiccation

-osmotic pressure

low temperature has a (physical methods of microbial control)

bacteriostatic effect

low temperature physical methods of microbial control

-refrigeration

-deep-freezing

-lyophilization (freeze drying)

high pressure physical methods of microbial control

denatures proteins

alters carbohydrate structure

desiccation physical methods of microbial control

absence of water prevents metabolism

osmotic pressure physical methods of microbial control

uses high concentrations of salts and sugars to create hypertonic enviornment; causes plamolysis

ionizing radiation

X-rays, gamma rays, electron beams

ionizing radiation

-ionizes water to create reactive hydroxyl radicals

-damages DNA by causing lethal mutations

-Gamma rays: penetrate deeply but require hours to sterilize

-high-energy electron beams: less penetration, but fast (seconds)

-used by food industry (spices, certain meats, vegetables)

-sterilization of pharmaceuticals, disposable dental and medical supplies, mail

gamma rays ionizing radiation

penetrate deeply but require hours to sterilize

high-energy electron beams ionizing radiation

less penetration, but fast (seconds)

food industry uses ionizing radiation

spices, certain meats, vegtables

radiaiton

-ionizing radiation

-non-ionizing radiation

non ionizing radiation classification

ultraviolet, 260 nm

non ionizing radiation

-damages DNA by creating thyamine dimers

-UVC “germicidal” lamps used in hospital rooms, nurseries, operating rooms, cafeterias

-effective, but does not penetrate; good for surfaces

-must avoid contact with eyes and skin

how does nonionizing radiation damage DNA

by creating thymine dimers

where are UVC lamps

“germicidal” lamps are used in hospital rooms, nurseries, operating, cafeterias

visible blue light classification non ionizing radiation

470 nm

visible blue light non ionizing radiation

kills a wide range of bacteria due to the formation of a singlet oxygen

microwaves non ionizing radiation

kill by heat; not especiall antimicrobial

sonication

-high frequency ultrasoundwaves to disrupt cell structures

-the disruption is achieved due to the rapid changes in pressure within the intracellular liquid

how is disruption achieved in sonication

due to the rapid changes in pressure within the intracellular liquid