Chapter 7: The Control of Microbial Growth

refers to bacterial contamination

the absence of significant contamination

• aseptic surgery techniques prevent the microbial contamination of wounds

removing and destroying ALL microbial life (bacteria, fungi, endospores)

killing Clostridium botulinum endospores from canned goods

destroying harmful microorganisms (not destroying spores)

• hand sanitizer

destroying harmful microorganisms from living tissue

the mechanical removal of microbes from a limited area

lowering microbial counts on eating utensils to safe levels

treatments that kill microbes

inhibiting, not killing microbes (stops bacteria from growing, does not kill them)

death

lack of growth

to denature enzymes

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

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

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

steam under high pressure

• 121 C at 15 psi for 15 min

• kills all organisms and endospores

• steam must contact the item's surface

reduces spoilage organisms and pathogens by heating materials for a short time

72 degrees C for 15 seconds (normal treatment for milk)

140 degrees C for 4 sec

(relatively heat-resistant) organisms survive

passage of substance through a screenlike material

• used for heat sensitive materials

remove microbes > 0.3 um in diamter

remove microbes > 0.22 um

• pore sizes of as small as 0.01 um are available, which can filter out viruses and large proteins

absence of water prevents metabolism

uses high concentrations of salts and sugars to create hypertonic environment; causes plasmolysis

ionizes water to create reactive hydroxyl radicals

• damages DNA by causing lethal mutations

damages DNA by creating thymine dimers

• concentration of disinfectant

• organic matter

• pH

• time

• evaluates efficacy of chemical agents

• filter paper disks are soaked in a chemical and placed on a culture

• look for zone of inhibition around disks

injure lipids of plasma membranes, causing leakage

• strong antibiotics

• basically punch holes in plasma membrane

a solution in aqueous alcohol

combined with organic molecules

• impairs protein synthesis and alters membranes

oxidizing agents; shut down cellular enzyme systems

• bleach: hypochlorous acid (HOCl)

• chloramine: chlorine+ammonia

• also impairs protein synthesis and alters membranes

60%

silver nitrate

inactive proteins by cross linking with functional groups

• used for preserving specimens in medical equipment

formaldehyde

used for contaminated surfaces and food packaging

• O3, H2O2 (hydrogen peroxide known as powerful oxidizing agent), and peracetic acid