Sterilization and Disinfection

Question 1

Sterilization

Answer 1

Kills all forms of microbial life, this is desireable but not always possible

Question 2

Antisepsis

Answer 2

Prevent sepsis or infection by killing the infectious bugs

Question 3

Disinfection

Answer 3

Same as antisepsis BUT APPLIED TO INANIMATE OBJECTS!! This is the key difference

Question 4

Sanitize

Answer 4

Reduction of the number of bugs

Question 5

Sterilizers (Sporicides)

Answer 5

Used to kill all forms of microbial life (virus, fungi, bacteria) and their spores

Question 6

Disinfectants

Answer 6

Used on hard non living surfaces to eliminate infectious bugs, but not necessarily the spores

Question 7

Sanitizers

Answer 7

Used to reduce BUT NOT ELIMINATE bugs from surfaces to a level considered safe by public health

Question 8

Antiseptics and Germicides

Answer 8

Used on living tissue (humans, animals) to prevent infection by inhibiting growth of bugs. THESE ARE CONSIDERED DRUGS AND ARE REGULATED BY FDA

Question 9

True or False?

Destruction of all bugs is equivalent to sterilization?

Answer 9

False.
Killing bugs in an IV solution can release their pyrogenic compounds and can cause shock. Solutions should be sterilized so that the bug never had a chance to grow in the first place

Question 10

Why is the extrapolation of quoting the time when all bugs are killed during sterilization not a good idea?

Answer 10

Bc even tho the sterilization of bugs and their spores exponential, their approach to 0 is asymptotic meaning their approach to 0 never really happens. The best you can do is quote a probability of a certain time when there are no more bugs alive.
Reason being is bc aggregates can survive longer ie polio vaccine.

Question 11

Why do spores pose a significant threat?

Answer 11

Bc they are relatively resistant to killing by all means of sterilization. They have a very low water content due to the presence of dipliconic acid

Question 12

When are endospores formed?

Answer 12

In response to nutrient depeletion.

Composition of spores are distinct, but they all contain the necessary tools to regenerate vegetative cells.

Question 13

Dipliconic Acid

Answer 13

An acid in endospores that is responsible for their low water content. It chelates Ca and uses it to stabilize their DNA via intercalation

Question 14

Sporulation

Answer 14

When the bug realizes that nutrients are sparse it will enter into this phase. It’s initiated by starvation.
GTP deficiency is the biochemical signal, and GTP synthesis is difficult

Question 15

What are the main sigma factors for sporulation regulation?

Answer 15

These factors are initiating proteins assoc with RNA polymerase.
Sigma 29-specific factor for B. subtilis, and directs transcription of sporulation specific genes
Sigma 55 is the factor for vegetative growth

Question 16

What are the three stages for vegetative growth of endospores?

Answer 16

Activation, Germination, Outgrowth

Question 17

Activation phase of vegetative growth

Answer 17

Generally by heat or chemicals, prob inactivating a critical protein

Question 18

Germination phase of veg growth

Answer 18

This phase is IRREVERSIBLE and requires good ol’ H2O. When it returns to this stage, it is now vulnerable and can be killed. No RNA or protein syn required.

Question 19

Outgrowth phase of veg growth

Answer 19

Active biosynthesis, transcription and translation

Question 20

What are the 4 spore forming Clostridium pathogens and what disease do they cause?

Answer 20

1.) C. tetani - Tetanus
2.) C. botulinum - Botulism
3.) C. perfringens - Gas gangrene
4.) C. difficle - C diff diarrhea (nosocomial infection)
All strains are anaerobic

Question 21

What are the characteristics of C. difficile?

Answer 21

Can exist as a spore or in veg state (toxin produced in veg state) but the spores are the main mode of transmission
In spore form, can survive on dry surfaces for months and resistant to heat, alcohol, acid, antibx, etc.
After ingestion, endospore germinate into veg state in colon and produce the toxin

Question 22

What form of C. diff produces the toxin?

Answer 22

Vegetative; but spores are main mode of transmission

Question 23

What are the chemical agents that damage cell membrane?

Answer 23

Surface active compounds
Phenols
Alcohols

Question 24

What are surface active compounds and what do they do?

Answer 24

These are agents that damage cell membranes and are:
Detergents, cationic and anionic agents (Zephiran and SDS, resp) and some non-anionic agents (Tween 80) that are not good and can actually serve as growth media.

Question 25

What are phenolic compounds and what do they do?

Answer 25

These are the gold standard in sterilization. They burn the skin, and therefore its a powerful biocide. Lysol (brand name disinfectant) Triclosan (antibacterial soaps, deodorants, toothpastes,etc) Halogenated diphenyls (hexachloroPHENE) soap that was withdrawn from OTC bc too strong baby

Question 26

What are alcohols and how do they disinfect?

Answer 26

Ethanol in concentrations btwn 50-70 bc water is needed for effective sanitation. 100% EtOH is not effective bc there's no water content. Isopropranol - more effective than EtOH but more toxic Witch Hazel - Alcohol solution from witch hazel tree ***Alcohols do not kill spores and thus are not suitable for sterlizing surgical equipment

Question 27

What are the four disinfecting agents that work by modify proteins and nucleic acids?

Answer 27

1. ) Heavy metals 2. ) Oxidizing Agents 3. ) Dyes 4. ) Alkylating Agents

Question 28

How are heavy metals effective in disinfection?

Answer 28

They are effective at low conc's Have a high affinity for SH groups and are its anti-microbial properties are reversed by Sulfhydryl compounds They are mercurials (mercurochrome) and Silver (Silver nitrate in eye drops for babies, and silver sulfadiazine for preventing infection in burn patients

Question 29

What is Ag Sulfadiazine used for and what is its mechanism of action?

Answer 29

It is used for preventing skin infections in burn patients and does this by modifying proteins and nucleic acids

Question 30

How are oxidizing agents effective in disinfection?

Answer 30

Oxidizing Agents are: Iodine - Effective against spores. It iodinites tyrosine residues on proteins. Betadyne (Iodophore) and KI which is painful and destructive so combine it with a detergent -Chlorine - basically bleach -Hydrogen Peroxide - sensitivity depends on the sensitivity to catalase

Question 31

How are dyes effective in disinfection?

Answer 31

Dyes work by intercalating into a bugs DNA. | Triphenylmethanes can work as a topical treatment for the skin and Acridines are for wound antisepsis

Question 32

How are Alkylating agents effective disinfectants?

Answer 32

These are very powerful and dangerous and are active against spores at the level necessary to kill veg cells From weakest to strongest: Formaldehyde is carcinogenic, can be used in vaccines and as a gas for decontamination Gluteraldehyde is 10x more effective than form and is a cold sterilant for surgical instruments (for the plastic ones that might melt in the autoclave) Ethylene Glycol is an unstable compound (3 membered ring) and therefore quite reactive. It works by PO4'n and N'n of nucleic acids. It is a biohazard

Question 33

What sterilant might you use to sterilize plastic surgical instruments that might melt in an autoclave?

Answer 33

Gluteraldehyde

Question 34

What are the physical agents that can be used to sterilize?

Answer 34

Heat Freezing and Thawing Radiation Filtration

Question 35

What is the physical agent used most often in medical settings to sterilize?

Answer 35

Heat with water. It's efficacy is dependent upon time, pressure, temp, and water. Sterilization is slower in the dry state bc the proteins will dry out and lose their polar groups and are then resistant to denaturation Tyndallization is a fractional sterilization method that is used to kill spores by inducing them to their vegetative state and then killing them in cycles Pasteurization reduces the number of microbes and kills most pathogens. Then refrigerate to retard the growth of remaining bugs

Question 36

How does UV and Ionizing radiation kill microbes?

Answer 36

It produces thymine dimers in DNA, but this damage can be repaired by SOS repair. However low penetrating power (dangerous at even low penetrance) limits the ise of it bc can cause damage to eyes and skin. Use for sanitizing rooms and tissue culture hoods Ionizing Radiaion have a direct and indirect effect. Direct is damaging bugs directly, and can even kill spores and can be used to sterilize surgical equipment and food. Indirect by causing free radical damage by producing ionizing water forming peroxides. THIS IS NOT EFFECTIVE AGAINST SPORES

Question 37

What is filtration and how can it be used as a disinfectant?

Answer 37

Bacteria and larger orgs can be removed from liquids. Removal of viruses require ultrafiltration which requires very high pressures to squeeze them thru the small pores in the filtration membrane.