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M & D > Chaper 13: Control of Microbial Growth > Flashcards

Chaper 13: Control of Microbial Growth Flashcards

1
Q

Sterilization

A

The complete removal or killing or rendering incapable ofreproduction of all living organisms and viruses

Ex) Filtration for removal
Radiation for rendering incapable of reproduction

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2
Q

Asepsis

A

sterility

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3
Q

Aseptic technique

A

things you do to maintain sterility

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4
Q

Sterilixation in an autoclave

A

transfer of heat from steam, wet heat for contact killing, and denaturazation of proteins/ DNA
-> steam gives deep penetration into matrixes

since killing increases with temperature autoclaves use a steaam temperature greater than normal BP of water (100c ar 1atm, 101kpa, 1bar)

Most autoclaves operate at 15pse or 1.1kg/cm^2 = 115kpa at whihc pressure water boild at 121C

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5
Q

Alternative temp pressure of autoclaves

A

some operate at 30psi (2.1 kg/cm^2) where the steam temperature is 134C

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6
Q

Why are such high temperatures used in an autoclave

A

Want to kill the most resistant organism which are the spores of Geobacillus sterothermophilus

death of microorganisms by heat is a first order reaction, the population dies by 90% or 1 log in a characteristic time called the decimal reduction time or D\
usually 6-2x D will reliably sterilize any object

thus the smaller D the shorter teh time to steriize

D declines with increaing temperature

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7
Q

Sterilization of spores

A

spores are usually the most difficult organims to kill

often spore are heat-resistant, rediation resistant and chemical resistant

Geobacillus stearothermophilus spores are often used due to extreem thermal tolerance, some D100 (decimal reduction time at 100C) in minutes.

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8
Q

D of select Bacillus spp.

A

B. sterothemophilus 46
B. licheniformic 24
B. anthracis 5
B. cereus 0.8

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9
Q

E. coli sterilization

A

vegitative cells of mesophiles are fairly heat-sensitive

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10
Q

Dry heat

A

For objects that do not contain water
glass, steel

for water insoluble products such as oils and fats

can melt or light some things on fire :(
also, if liquid is in a closed vessel will blow up

not as efficient or reliable as moist heat

Hours instead of minutes

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11
Q

UV radiation

A

260nm

damaging DNA => TT dimer, during replication DNA pol will stall at the dimer. DImer can be repaired (error prone repair leads to mutations)
=> replicaiton stalls are mutations can be fatal

non-ionizing
poor penetration, surface sterilization only

water, air and surface (stainless steel and plastics) sterilizaiton

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12
Q

Ionizing radiation

A

Xrays (from Co 60), gamma and electron beams from

good penetration throughout food and containers, only really stopped by thick layers of lead an concrete

double-stranded DNA breaks

free radical production

safetly concern due to long life free radicals

Co^60 gamma radiation

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13
Q

Ethylene DIoxide

A

gas

several hours exposure ar mild temperatures

good for heat sensitive items

bulk items

stuff needs to be porous

leaves a residue

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14
Q

Purpose of disinfectants

A

reduction in the population of microorganisms to a reasonably safe level

removal, killing or inhibition of microorganisms whihc are pathogenic

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15
Q

Types of disinfectants

A

phenol

bis-phenols

heavy metals

halogens

hypochlorite

iodine mixtures

chlorohexadine

ethanol 70%, isopropanol 70%

quaternary ammonium compounds

alkylating agents

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16
Q

bis-phenols

A

benzyl-chlorophenol and triclosan

anti-microbial but sate for human skin
=triclosan which is an antiseptic and a disinfectant (probably a carcinogen)

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17
Q

heavy metals

A

mercury, silver, copper, nickel

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18
Q

halogens

A

chlorine gas, chloramines and bromine

chloride dioxide or in salts

good for water treatment in potable water

disinfected in water

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19
Q

ammonium compounds

QUATs

A

quaternary ammonium compounds a N+ atom with 4 long chain alkyl groups and a chloride ion

detergents, cause fats to solvate in water, destroy membranes, and denature proteins.

good against envalope virues, but not naked viruses cause they dont have that lipid envalope

spreads well, breaks the surface tension of water

not volatile, so they do leave a residue.

good for cleaning surfaces

industrial and commercial settings (hospitals and food processing plants)

(the most important one on this list)

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20
Q

alkylating agents

A

covalently modify DNA and protiens

not used very much

formaldehyde, gluderaldehyde

beta propionolactone (BPA)
= inactivating viruses in samples

o phthaladehyde (OPA)

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21
Q

Antiseptic

A

an antimicrobial compound (disinfectant) which is safe for contact with human skin

antibacterial, antifungal, not so much antiviral

ethanol and hydrogen peroxide but these are not really safe for contact except at low concentrations and low contact time

soap and detergents

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22
Q

sanitization

A

reduce the number of microorganisms to a defined safe level

23
Q

phenols

A

numbs pain, in anti ithcing creams

toxic, corrosive, carcinogen, leaves a residue

24
Q

silver

A

long history as a antibacterial agent

silver cutlery, plates and drinking glasses

not very toxic, and does not dissolve in water

silver nitrate is used to today
= an oxidizing agent for things like cold sores
=caterizes wounds
= also used in eyedrops to prevent blindness from sexually transmitted diseases

25
Q

Copper

A

poor mans silver

good b/c it is maliable

not as effective as silver, but cheaper

26
Q

nickle

A

an even poorer mans silver

27
Q

mercury, cadmium, lead, and tungston

A

good b/c antimicrobial, but are however, toxic

ppl used use salversan, which is an organic mercury salt
= was very good for treating STDs especially syphallis

28
Q

bleach

A

need to make your working solution each day (0.5 - 1%)

most of the bleach ends up using their disinfecting power oxidizing organic materiual, protiens etc. not the infectious agent :(

29
Q

iodine

A

iodine mistures or iodine salt + a wetting agent b/c iodine doesn’t dissolve or spread very well

skin disinfecteds, oxidizing agents, but not very good ones

30
Q

alcohols as disinfectents

A

ethenol and isopropanol

used because these are the bois that are soluable in water

100% is bad, because they dehydrate the cells and end up not kiling them

70% is good, below is bad.

strip membranes, denature protiens

not good agaisnt spores or mycobacterium

evaporates and is very flammable or explosive not good for bacteria in orgnaic mateiral like blood

no residue, low surface tension, can flow into cracks

31
Q

perodixes

A

surface use

many different types

disinfecting powers will degrade over time

react with metals like iron, and will decompose to water

better than ethanol in things like blood

oxidizing agents

32
Q

difference between a soap and a detergent

A

detergents are not ppt our by metals in water (like Ca2+)

detergents are better than soaps

kills naked and envaloped viruses

33
Q

Contact time and concentration for disinfectants

A

contact time and concentration are important factors- generallly inverse to each other

indicator organisms (Usually ATCC strains, 1 G+ and 1G- plus Pseudomonas aeruginosa plus Mycobacterium)
=non-pathogenic mycobacterium
=might also include spores, fungi, naked or envalopoed viruses

often contain a surfactant to reduct surface tension of the disinfectant

34
Q

Pasteurization

A

heat applied for a long period of time at a low temp

moist heat below 100c

used on heat sensitive fluids like milk, beer and fruit juices

heat denatures and ppt out proteins

35
Q

milk pasteurization

A

63c for 30 min

to kill of mesophilic and psycotrophic pathogens

to kill/ reduce the number of bovine tuberculosis, and reduce the numbers of staph aureus and enterics

36
Q

hihgh temp/ flash pasteurization

A

72c for 15 sec

37
Q

purpose of pasteurization

A

kills pathogens and reduces the total populaiton of bacteria (does not kill all bacteria or kills spores)

main purpose is to slow the rate of spoilage

to kill of mesophilic and psycotrophic pathogens

38
Q

UHT

A

ultra high temp pasteurization

high temp, lower contact time

kill more organsims, quicker without degrading the quality of the product

like 85C for 30sec

hot quick, then cool it back down quick

39
Q

Tyndallization or Fractional Steralization

A

put the product into a bath of a product that is a temp high enough to kill a pathogen/ vegatative cells for a short period of time.

let rest for a bit, spores become vegatative cells, then treat a second time

repeat the process at least 3 times and upwards fo 5/6 times

steralize the liquid without reaching 100c

40
Q

Refrigeration and Freezing

A

slows the growth of most mesophiles

commercial refrigerators operate at 4-8C

Freezing stops metabolism and chemical deterioration at -18c
=> because cells are full of solutes, 0c does not nessecarily freeze cells, but -18c does

freezing may slowly kill bacteria but ice crystal formation may also dehydrate them (dehydrated cells dont die)
=> slow freezing= ice crystal formation= death sometimes

can quick freeze via liquid nitrogen to prevent ice crystal formation and thus desiccation.

sublimaiton in the freezer over time can lead to desiccation

41
Q

Are most human pathogens psycrophiles or mesophiles

A

mesophiles

some are pathogens that can grow/ cross the range of mesophile and psycrophiles

obvs mesophiles cause they grow in the human body at 37c

42
Q

Pressure

A

high pressure can kill vegetative cells but not as effective against spores

hyperbaric oxygen treatment to kill anaerobes

100+atm

can steralize thing with this

liquids and semiliquid media

expensive

hyperbaric chamber and high pressure to 3atm to kill clostridium species under slightly higher O2 conc.
=> O2 diffuses into body to kill the anaerobe

43
Q

Desiccation

A

removal of free water inhibit metabolism

does not necessarily kill bacteria

includes natural dehydration (sun drying) and freeze-drying (lyophilization, -80c and put under a vaccum suich that the water sublimes and is sucked offf via a vaccum pump. often used to steralize vaccines. can also be used to keep bacteria long time in storage, they are protected wioth things like skim milk whihc is known as a cryoprotectant)

decreaces water activity

44
Q

Water activity

A

is a measurement of the avalibility of water to an organism

for pure water aw = 1.00

as you add solutes, the water activity decreased (less free water, water becomes bound to water)

this is why you add sugar and salt to things like jam

less free water, those h-bonds cant form

desiccation can decrease water activity by adding high concentrations of solutes such as sugar and salt

45
Q

Free water

A

water that can be removed from an object without heat

water that is not bound to proteins and such

non-solvating water

46
Q

aw differences between water and fungi

A

bacteria are more sensitive to free water loss than fungi

most bacteria 0.91 - 0.98
-> can uses these values to see what foods bacteria can or cannot grow on

most yeast 0.88

  • > why fungi can grow on bread, baked goods and grains, and cheese
  • > not on meats because the lipids on meats are protective
47
Q

Salt, aw and food fermentation

A

additon of salt decreases water activity

can prevent to grow of organisms that require higher water activity like pseudomonas and enterobacteriaecae but allow for the growth of lactobacilliaceae

48
Q

Osmophilic yeast

A

aw 0.62

=Zygosaccharomyces rouxii

is an osmphillic yeast

is a real problem in things like fruit juice

49
Q

Filtration

A

useful for gases and liquids

for air, HEPA (high efficiency particulate air) filtration is used

filter material can capture particles of 0.3um size with 9.997% efficiency (can vary depending on pore size)

50
Q

liquids can be sterilized by membrane filtration

A

usually pore size of 0.2um to remove bacteria

51
Q

Absolute filtration

A

= if undamaged filter will remove 100% of particles greater in size thatn the normal pore size of the filter

liquid filtration

52
Q

ultrafiltration (UF)

A

to remove viruses (lots of variation in virus size, however, if you select for a parva virus, no others will get through cause they are so small)

can be done at low temp

will not damage the liquid you are steralizing (protein type theraputics, sill however lead to some loss since some proteins will stick)

pore size = 0.01um

liquid filtration

53
Q

depth filters

A

porous filtration medium which remove partivles throughout the medium rather than just on the top

diatomaceous eath

paper (cellulose)

liquid filtraiton

M & D (18 decks)

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