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Microbiology-1 > Sterilization & Disinfection > Flashcards

Sterilization & Disinfection Flashcards

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1
Q

Sterilization/Sterilizers (Sporicides)(EPA)

A

-Kill ALL forms of microbia life

Desirable but not always fesible/

-Used to eliminate all forms of microbial life: fungi, viruses, bacteria, and their spores

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2
Q

Antisepsis/ Antiseptics & Germicides (EPA)

A
  • Prevent sepsis (infection) by killing infectious microorganism/
  • Used on living humans or animals to prevent infections by inhibiting the growth of microorgsm. Considered drugs by FDA
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3
Q

Disinfection/Disinfectants (EPA)

A
  • same as antisepsis but applied to inanimate objects/
  • Used on hard inanimate surafaces to destroy or inactivate infectious fungi and bacteria but not necessarily spores
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4
Q

Sanitize/Sanitizers (EPA)

A
  • Reduce the number of microorganism/
  • Used to reduce, but not necessarily eliminate microorgsm from inanimate inanimate envirn to levels considered safe by public health code
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5
Q

which agents are non-selective and can damage human cells aswell?

A

sterilization and disinfection

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6
Q

Destroying ALL Microorganism vs Sterilization

A
  • NOT equivalent
  • killing microorganism in an intravenous solution can release pyrogenic compounds and cause toxic shock
  • Solutions shouls be sterilized so bacteria can NEVER grow.
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7
Q

Death rates during sterilization are….

A
  • Exponential
  • killing of E. Coli by phenol is the gold standard
  • typical of most bacteria
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8
Q

Death of Spores are…

A
  • Exponential but much SLOWER
  • killing of B. subtilis
  • specific rate constant is 1000 fold less
  • require high [phenol] and temp
  • true for all means of sterilization
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9
Q

Is there a time in which 0 microorganism remain?

A
  • there is no absolute time
  • the approach to 0 is asymptotic
  • only the probability that a sample will have 0 microorgasm can be stated
  • even predictions may be inaccurate (Kinetics vary & affected by medium composition)
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10
Q

Can sterilization kill spores?

A
  • Spores are relatively resistant to killing by all means of sterilization
  • ex. of spores: B. subtilis, Clostridia (botulinum, tetani), Bacillus anthracis
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11
Q

How are endospores formed?

A
  • in response to nutrient depletion
  • composition of spores is distinct: spores contain everything necessary to regenerate vegetative cells
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12
Q

What is the basis of bacyerial spore resistance?

A
  • extremely low water content
  • due to presence of dipicolinic acid
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13
Q

How does Dipicolinic Acid help spores become resistant to sterilization?

A
  • responsible for low H2O and high Ca2+ content of spores
  • unique in spores
  • chelates Ca2+
  • stabilizes DNA by intercalation
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14
Q

How is sporulation initiated? What becomes deficient?

A
  • by starvation
  • specific biochemical signal: GTP deficiency
  • unfavorable environment lead to decrease amino acids, causing increased ppGpp, which inhibits GTP synthesis
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15
Q

How is sporulation genetically regulated?

A
  • specialized sigma factors
  • factors are initiating proteins associated w/ RNA poly.
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16
Q

What are some sigma factors involved in sporulation?

A

σ29: in B. subtilis, directs transcription of sporulation specific genes

σ55: factor for vegetative growth

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17
Q

What are the steps in regeneration of vegetative cells?

A
  1. Activation
  2. Germination
  3. Outgrowth
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18
Q

How is activation initiation during the regenration of veg. cells?

A
  • generally by heat or chemicals
  • unknown mechanism
  • inactivation of critical protein is possibilty
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19
Q

What are some features of germination during the regenration of veg. cells?

A
  • irreversible
  • requires water
  • accompanied by loss of resistance
  • does not require nucleic acid or protein synthesis
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20
Q

what occurs in Outgrowth phase during the regenration of veg. cells?

A
  • active biosynthesis
  • ordered transcription & translation
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21
Q

What are some examples of anaerobic-spore forming bacteria?

A

Clostridium:

  • tetani (tetanus)
  • botulinum (botulism)
  • perfringens (gas gangrene)
  • difficile (deficile- associated diarrhea)
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22
Q

What does the vegetative form vs spores of C. difficule produce?

A

-Toxins vs main mode of transmission

23
Q

How are the spores of C. difficile transmitted?

A
  • Nosocomial (hospital-acquired) infections transmistted by health personnel
  • survive on dry surface for several months
  • resistance to heat, acid, ab, alcohol hand disinfectants.
24
Q

What happens after C. difficile ingestion?

A

Spores germinate into vegetative cells in colo nand produce toxin

25
Q

How do you control a C. difficile infection and what is the proper hand hygiene?

A
  • Isolation in private room
  • wear gloves and gown
  • Hand Hygiene: wash hands with soap and water, Alcohol disinfectans DO NOT kill or remove spores.
26
Q

What are some chemical agents that damage cell membrane?

A
  1. surface active compounds
  2. phenolic compounds
  3. alcohols
27
Q

What are 4 types of surface active compounds?

A
  1. detergents.
  2. cationic agents (zephiran)
  3. anionic agents (SDS)
  4. Nonionic agents (Tween 80, no effective, may promote growth)
28
Q

What are some phenolic compounds?

A

Gold standard

  1. alkyl and chloro phenols (Lysol, Triclosan)
  2. halogenated diphenyls (hexachlorophene)
29
Q

What are 3 alcohols that damage the cell membrane?

A
  1. 50-70% ethanol (primary agent in hand disinfect)
  2. isopropanol (more effective than EtOH but more toxic)
  3. witch hazel (solution of an extract from leaves and bark)
30
Q

Are alcohols suitable killing spores?

A

No, also NOT suitable for sterilizing surgical instruments

31
Q

What 3 compounds denature proteins?

A
  1. Organic acids(Benzoic & proprionic acids)
  2. Preservative in food and pharmaceuticals
  3. alkyl esters of organic acids (like alkul substituted phenols)- non toxic orally, hydroluzed to p-hydroxy-benzoate)
32
Q

What are 4 compounds that modify proteins & nucleic acids?

A
  1. Heavy Metals
  2. Oxidizing agents
  3. Dyes
  4. Alkulating agents
33
Q

How do heavy metals work to mod proteins & nucleis acids?

A
  • high affinity for SH groups
  • effective at [low] (1ppm)
  • reversed by sulhydryl compounds
  • mercurials (mercurochrome)
  • silver compounds (ex. silver nitrate-used to prevent Gonococcal infect in new borns, and in silver silfadiazine-prevent infect in skin burns)
34
Q

What are components of the oxidizing agent Iodine?

A
  • iodine combines w/ proteins and iodinates try residues
  • iodine prep:
    - tincture of iodine (2%I2 +2% NaI in 50-70%
         EToH)

   - idophores (I2 in surfactant)-betadyne
   - KI painful and destructive, combine with  

     detergent is better

****Effective against spores!

35
Q

What are some types of oxidizing agents? What do they do?

A
  1. Iodine
  2. Chlorine & hypoclorites
  3. Hydrogen Peroxides & organic peroxides
    - they modify proteins and nucleid acids
36
Q

What are components of the oxidizing agent Chlorine (Cl2) & hypochlorites?

A
  • chlorox (bleach)
  • yield hypochlorous acid (HOCl)
  • Cl2 + H20–> HCI + HOCl
37
Q

What are components of the oxidizing agent H2O2 & organic peroxides?

A
  • sensitivity to H2O2 depends on the absence of catalase activity
  • 3% solutions is one agent for contact lenses
38
Q

What are 2 types of dyes that help mod proteins & nucleis acids?

A

1. triphenylmethanes

  • mode of action undefined
  • tropical treatment for skin
  • Brilliant green, malachite green, crystal violet

2. Acridines

  • wound antisepsis
  • mutagenic bc they insert in DNA
  • proflavine, acriflavine
  • carcinogenic
39
Q

What are 3 examples of alkylating agents that help modify proteins and nucleic acids?

A

formaldehyde, glutaraldehyde, ethylene oxide

40
Q

How effective are alkalating agents in killing microbes?

A
  • some of the most effective
  • active against spores at levels equivalent to those necessary to kill veg cells.
41
Q

What is the function of formaldehyde?

A
  • used as an alkylating agent to mod proteins and nucleic acids
  • Reacts with CO2-, OH, and SH groups
  • Aqueous solutions is formalin (37% solution)
  • 0.2-0.4% used to inactivate virus to make vaccines
  • used as gas for decontamination
  • carcinogenic
42
Q

What is glutaraldehyde used for? What does it react with? How effective is it?

A
  • Alkylating agent to modify proteins & NA
  • Reacts with SH & NH groups
  • 10X as effective as formaldehyde
  • cold sterilant for surgical instruments
43
Q

What is ethylene oxide used for? What does it form? How stable is it?

A
  • Alkylating agent to modify proteins & NA
  • forms hydroxyethyl derivative (CO2-, OH, SH & phenolic groups of proteins) (PO4 & N of Nucleic acids)
  • Biohazard (unstable, highly reactive)
44
Q

What are some physical agents against microbes?

A
  1. heat
  2. freezing & thawing
  3. radiation
  4. filtration
45
Q

How is heat effective against microbes?

A
  • Physical agent used most often, esp. in med setting
  • sterilization w/ heat dependent on time, T, P, H2O
  • sterilization slower in dry state (proteins lose polar groups and become resistant to denaturation)
46
Q

What are 2 other methods using heat?

A
  1. tyndallization
  2. pasteurization
47
Q

How does tyndallization work?

A

physical agent

  • a fractional sterilization method
  • heat 80-100C for 30 min on 3 consecutive days
  • spores activated then killed in following heating cycle
48
Q

how does pasteurization work?

A

physical agent

  • reduces # microorgansm & kills most pathogens
  • heat to 62C for 30 min
  • used for milk
49
Q

What is freezing and thawing used for and should it be used for sterilization?

A

not reliable

used to preserve bacteria in lab

not used for sterilizatoin

50
Q

What does UV radiation do to DNA? How can it be repaired? What is it used for?

A
  • produces pyrimidine dimers
  • damage can be repaired by photoreactiviation or SOS repair
  • Used for sanitizing rooms & tissue culture hoods
  • low penetrating power limits use
  • can damage eyes & skin
51
Q

What does Ionizing radiation do? what is it used for ?

A
  • gamma, X rays and accelerated e-
  • direct effect (directlt damages macromolecules, kills spores)
  • used for sterilization of surgical supplies and food
52
Q

What is the indirect effect of ionizing radiation? is it effective against spores?

A
  • from ionization of H2O
  • if o2 is present, H2O2 and organiz peroxides are formed
  • not effective against spores
53
Q

How does filtration work?

A
  • bacteria and larger microorgasm easily removed from liquids (effectve pore size 0.22 microns)
  • removal of viruses requires ultrafiltration and High P

Microbiology-1 (8 decks)

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