Sterilization & Disinfection Flashcards
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
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
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
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
5
Q
which agents are non-selective and can damage human cells aswell?
A
sterilization and disinfection
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.
7
Q
Death rates during sterilization are….
A
- Exponential
- killing of E. Coli by phenol is the gold standard
- typical of most bacteria
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
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)
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
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
12
Q
What is the basis of bacyerial spore resistance?
A
- extremely low water content
- due to presence of dipicolinic acid
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
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
15
Q
How is sporulation genetically regulated?
A
- specialized sigma factors
- factors are initiating proteins associated w/ RNA poly.
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
17
Q
What are the steps in regeneration of vegetative cells?
A
- Activation
- Germination
- Outgrowth
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
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
20
Q
what occurs in Outgrowth phase during the regenration of veg. cells?
A
- active biosynthesis
- ordered transcription & translation
21
Q
What are some examples of anaerobic-spore forming bacteria?
A
Clostridium:
- tetani (tetanus)
- botulinum (botulism)
- perfringens (gas gangrene)
- difficile (deficile- associated diarrhea)
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
How do you control a C. difficile infection and what is the proper hand hygiene?
- 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
What are some chemical agents that damage cell membrane?
1. surface active compounds
2. phenolic compounds
3. alcohols
27
What are 4 types of surface active compounds?
1. detergents.
2. cationic agents (zephiran)
3. anionic agents (SDS)
4. Nonionic agents (Tween 80, no effective, may promote growth)
28
What are some phenolic compounds?
Gold standard
1. alkyl and chloro phenols (Lysol, Triclosan)
2. halogenated diphenyls (hexachlorophene)
29
What are 3 alcohols that damage the cell membrane?
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
Are alcohols suitable killing spores?
No, also NOT suitable for sterilizing surgical instruments
31
What 3 compounds denature proteins?
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
What are 4 compounds that modify proteins & nucleic acids?
1. Heavy Metals
2. Oxidizing agents
3. Dyes
4. Alkulating agents
33
How do heavy metals work to mod proteins & nucleis acids?
- 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
## Footnote
What are components of the oxidizing agent Iodine?
- 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
What are some types of oxidizing agents? What do they do?
1. Iodine
2. Chlorine & hypoclorites
3. Hydrogen Peroxides & organic peroxides
- they modify proteins and nucleid acids
36
What are components of the oxidizing agent Chlorine (Cl2) & hypochlorites?
- chlorox (bleach)
- yield hypochlorous acid (HOCl)
- Cl2 + H20--\> HCI + HOCl
37
## Footnote
What are components of the oxidizing agent H2O2 & organic peroxides?
- sensitivity to H2O2 depends on the absence of catalase activity
- 3% solutions is one agent for contact lenses
38
## Footnote
What are 2 types of dyes that help mod proteins & nucleis acids?
**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
What are 3 examples of alkylating agents that help modify proteins and nucleic acids?
formaldehyde, glutaraldehyde, ethylene oxide
40
How effective are alkalating agents in killing microbes?
- some of the most effective
- active against spores at levels equivalent to those necessary to kill veg cells.
41
What is the function of formaldehyde?
- 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
What is glutaraldehyde used for? What does it react with? How effective is it?
- Alkylating agent to modify proteins & NA
- Reacts with SH & NH groups
- 10X as effective as formaldehyde
- cold sterilant for surgical instruments
43
What is ethylene oxide used for? What does it form? How stable is it?
- 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
What are some physical agents against microbes?
1. heat
2. freezing & thawing
3. radiation
4. filtration
45
How is heat effective against microbes?
- 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
What are 2 other methods using heat?
1. tyndallization
2. pasteurization
47
How does tyndallization work?
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
how does pasteurization work?
physical agent
- reduces # microorgansm & kills most pathogens
- heat to 62C for 30 min
- used for milk
49
What is freezing and thawing used for and should it be used for sterilization?
not reliable
used to preserve bacteria in lab
not used for sterilizatoin
50
What does UV radiation do to DNA? How can it be repaired? What is it used for?
- 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
What does Ionizing radiation do? what is it used for ?
- gamma, X rays and accelerated e-
- direct effect (directlt damages macromolecules, kills spores)
- used for sterilization of surgical supplies and food
52
What is the indirect effect of ionizing radiation? is it effective against spores?
- from ionization of H2O
- if o2 is present, H2O2 and organiz peroxides are formed
- not effective against spores
53
How does filtration work?
- bacteria and larger microorgasm easily removed from liquids (effectve pore size 0.22 microns)
- removal of viruses requires ultrafiltration and High P
