lecture 3- controlling microorganisms

Question 1

disinfection

Answer 1

destroys most microbial life, reducing contamination on inanimate surfaces

• destroy vegetative (growing) cells
• doesn’t kill bacterial spores
• conditions too harsh to use on people

Question 2

antisepsis

Answer 2

destroys most microbial life, reducing contamination on a living surface
-Use “antiseptics”, chemical agents that kill microbes

Question 3

sterilization

Answer 3

destruction of all microbial life

-used for inanimate objects, never living tissue as too harsh

Question 4

what are cells?

Answer 4

packages of water, genetics, proteins, sometimes have cell wall

Question 5

highest resistance

Answer 5

• bacterial endospores
• pirons (infectious proteins)
• no moving parts, low enzymes therefore few targets to kill

Question 6

moderate resistance

Answer 6

• Protozoan cysts (kind of like a spore)
• fungal sexual spores,
• naked viruses (does not have a membrane)
• resistant bacteria (like some Gram+)

Question 7

least resistance

Answer 7

• growing bacterial cells (expire quickly without water)
• growing eukaryotic cells
• enveloped viruses (c/membrane - HIV)
• yeast

Question 8

how are viruses resistant?

Answer 8

• dont need food

- many don’t need water

Question 9

how are bacterial spores resistant?

Answer 9

• some Gram-positive make spores
• don’t need food
• strong protein coat protects genetic material and enzymes inside
• low water content

Question 10

how are some bacteria resistant?

Answer 10

ESP. Gram +

• thick cell wall
• resist desiccation (drying)

Question 11

how are eukaryotes resistant?

Answer 11

• protozoan cysts
• fungal spores
• Strong protein coats
• Don’t need water

Question 12

how is microbial death characterized?

Answer 12

• cell structures dysfunctional (irreversible damage)
• cant reproduce
• Need microbicidal agent

Question 13

-cidal

Answer 13

killed

Question 14

-static

Answer 14

not killed, won’t grow in mass numbers, removes them

Question 15

what affects microbial killing rate

Answer 15

• number of organisms (harder to kill lots - fewer cells, less sterilization time)
• type of microbial population
• concentration of decontaminating agents (less concentrated, less killing)
• mode of action for agent
• presence of solvents, organic matter, and inhibitors
• environment temp and pH

Question 16

how do you kill microbes?

Answer 16

target weaknesses
-denaturation of:
cell wall
cell membrane
enzymes
genetic material

Question 17

MOA: targeting cell membrane

Answer 17

-when cell membrane is disrupted, selective permeability is lost - cytoplasm leaks out causing cell death

Question 18

MOA: inhibiting enzyme functioning

Answer 18

• proteins have a specific shape (native shape) when this is disrupted the protein becomes denatured
• enzyme active sites can’t accept substrate to function

Question 19

explain the difference between moist heat and dry heat and how they kill microbes

Answer 19

moist heat is for coagulation and denaturation
dry heat removes water from organisms (incineration)

*moist heat is more destructive b/c water has ability to kill proteins within organism (takes less time sterilize)

Question 20

how does the autoclave work?

Answer 20

high pressure concentration of steam creating a destructive moist heat

Question 21

what is pasteurization used for? how is it accomplished?

Answer 21

• disinfect beverages
• heat is applied to liquid to kill pathogens, but doesn’t denature proteins (flavour and texture in tact)
• doesnt kill endospores, and it is NOT STERILE

Question 22

what are the two methods of pasteurization?

Answer 22

flash: expose to 71.6°C for 15 seconds
Batch: expose to 63°C to 66°C for 30 minutes

Question 23

MOA: Ionizing radiation

Answer 23

ionizing: energy from-rays, gamma-rays and high energy UV light to liberate e- from atoms
* can penetrate and get hidden microbes, can inhibit proteins

Question 24

what is ionizing radiation used to sterilize?

Answer 24

food products, medical products

Question 25

advantages of ionizing radiation

Answer 25

speed, penetrating power, no heat

Question 26

Non-ionizing radiation

Answer 26

-causes mutations in DNA leading to cell death or function changes–> caused by low energy UV (thats why you wear sunscreen)

Question 27

uses of non-ionizing radiation

Answer 27

• disinfection rather than sterilization
• Hospital rooms, operating rooms, schools, food prep areas, dental offices
• Treat drinking water or purify liquids

Question 28

MOA: Phenols

Answer 28

• one initial disinfectants used
• very penetrating
• kill cells and spores and most viruses
• denature proteins, membranes, cell walls

Question 29

MOA: Reactive ions

Answer 29

includes chlorine, iodine, fluorine
-very penetrating
-kill cells, spores and most viruses
-strong oxidizers: they are hungry for electrons
(denature proteins and DNA)

Question 30

MOA: Alcohol

Answer 30

70% ethanol kills cells
better than 100% alcohol
b/c breaks membranes and denatures proteins.
**30% water contributes to coagulation
-Does not destroy bacterial spores
-More effective against enveloped than naked viruses

Question 31

MOA: detergents and soaps

Answer 31

detergents disrupt membranes (penetrates into membrane allowing cytoplasm to leak out)
-polar and non polar portions to help penetrate into cell membranes

Question 32

how is filtration used to decontaminate liquids

Answer 32

• remove cells, but not most viruses

- non-denaturing and helpful for making serum, vaccines, antibiotics, purify water