module 14

 

Know the difference between sterilization, disinfection, antisepsis, degerming, and sanitization.

Sterilization-kills all forms of life and destroys endospores and viruses

Commercial Sterilization-sufficient heat treatment to destroy endospores of C. botulinum in canned foods

Disinfection-destruction of vegetative pathogens

Antisepsis-disinfection on living tissue

Degerming-removal of microbes from a limited area

Sanitization-lowering the number of microbes

What factors influence bacterial cell death (if exposed to a disinfectant for example) ?

Number of microbes-more takes longer

Microbial characteristics-endospores, mycolic acid, porins

Environment-if presence of organic matter which inhibits chemicals; part of biofilm

Time of exposure

Normally, what do we target to kill bacteria? 

Plasma membrane, proteins, nucleic acids

What is autoclaving?  How does it kill bacteria?  How do we get the temperature to 121^oC?  When would we use autoclaving?  Why aren't food products autoclaved?

Moist heat

Sterilization

121 at 15 psi for 15 min

Kill/destroy all microbes/endospores due to high temperature denaturing proteins/destroying membrane

Used for liquids and other items

Not used for food because it would denature the proteins and caramelize the sugars which would change the taste of the food product

How does autoclaving differ from pasteurization? What are the three types of pasteurization? When would we use pasteurization?

Pasteurization does not make anything sterile

1. Lower temp for a longer time (63 degrees for 30 min)

2. High temp for short time (72 degrees for 15 sec)

3. Ultra-high temp (140 degrees for 5 sec)

This is used for food products like milk

 

What are the three types of dry heat sterilization?  When would each be used?

Flaming-1200 degrees (flaming a loop)

Incineration-1000 degrees (hospitals)

Hot air sterilization-170 degrees for 2 hours (glassware but no liquids)

What is filtration?  When would you use filtration?

The physical removal of microbes

Used when a material can not have heat sterilization

How does low temperature inhibit cell growth? 

Low temperature (0-7 degrees) are bacteriostatic which slows down bacterial growth but does not stop or kill~has no effect on psychotrophs

How does dessication inhibit cell growth?  What type of cells will be most sensitive to drying?  How does drying compare to osmotic pressure?  What type of solution causes plasmolysis? 

Without water, the metabolism shuts down growth

Most sensitive=Treponema and Neisseria gonorrhoeae

Not sensitive=Mycobacterium (has mycolic acid)

Osmotic pressure is based off of solute concentration, but both shut down cell growth

A hypertonic solution causes plasmolysis

What are the two types of radiation that are being used for sterilization?  How do they differ from each other?  When would you use each type?

Ionizing-Gamma or X-rays; high energy; damages DNA; could be used for meat but the public does not like the idea (no understanding)

Nonionizing-UV light; Damage DNA by thymine dimers; used for surface sterilization

What are the major differences between antibiotics and disinfectants?

1.     Disinfectant

a.      Location- Extrenal only

b.     Target- Non specific in plasma membrane

c.      Concentration- 10 mg/ml, more

d.     Source- Organic chemist

e.      Simple structures

2.     Antibiotics

a.      Location- external/internal

b.     Target- really specific, one site of activity

c.      Concentration- 10 ug/ml, less

d.     Source- microbes

e.      Complex structures

What is the similarity and difference between a disinfectant and an antiseptic?  Be able to give an example of each.

1.     Disinfectant- product that does destruction of vegetative pathogens on inanimate objects

a.      lysol

2.     Antiseptic- product that does destruction of vegetativepathogens on living tissue

a.      listerine

 

How is disinfectant efficiency (activity) measured?  Give two examples and describe/list steps of each.

1.     Use-dilution test

a.      Take metal rings

b.     Rings into product- concentration going to sell at

c.      Rings into growth media

2.     Filter paper method

a.      Similar to Kirby Bauer method

Why is phenol no longer used for surgery as it was when first introduced by Joseph Lister?  What does phenol target to control microbial growth?  Is phenol still used today?  If so, in what would you look to find it?

 

Phenol is toxic

1.     Carcinogen

2.     Neurotoxin

3.     Irritant

Still used for surfaces, instruments, and skin surfaces

Targets plasma membrane

Common phenolic- O-phenylphenol

 

What are two types of bisphenols? 

2.     Hexachlorophene-pHisoHex

3.     Triclosan- ingredient was in antibacterial soaps, toothpastes, cutting boards, ect

5.     Stops enzyme for fatty acid production

6.     FDA banned use in 2016 in most products

a.      Bacteria started to evolve around-resistant

b.     Affects human hormones

 

What are the two types of halogens?  Where would you expect each of them to be used today?  How does each work on the cell?

 

1.     I2

a.      Binds amino acids like tyrosine and targets plasma membranes

b.     Effective against many endospores

c.      Antiseptic as iodophor-iodine and alcohol

2.     Cl2

a.      Must combine with water-hypochlorous acid

                                                  i.     Cl2 + H2O <---> H+ + Cl- +HOCl

b.     Strong oxidizer of enzymes

c.      Swimming pools, s\drinking water, ect

What is the activity of alcohols? 

1.     Does not destroy endospores

2.     Denatures proteins and causes plasma membrane problems

3.     Evaporates quickly

4.     Skin- mostly degerming shots

How do heavy metals inhibit cell growth (what action and define this)?  Give some examples of heavy metals

1.     Oligodynamic action

a.      Just need a small amount to have microbial effect

b.     Silver, mercury, copper

c.      Silver nitrate- eye drops for newborns- not used much if at all

d.     Metal ions denature cell proteins

What does a “regular” detergent do?

What is a cationic detergent, and how do they work to control cell growth?

1.     Good at mechanical removal of microbs-decreases surface tension

2.     Emulsification of oil/dirt

3.     Cationic detergents- disrupts membranes, called quaternary ammonium compounds (quats)

How does an aldehyde prevent bacterial growth?  Where would you use aldehydes to prevent bacterial growth?

1.     Inactivates proteins

2.     Glutaraldehyde- for equipment use

3.     Embalming fluids- formaldehyde

 

What type of gas is used to sterilize materials?  What is the problem with using this type of gas to sterilize materials? 

 

1.      Ethylene oxide

2.      Denatures protein

3.      Destroys endospores and all microbs- 4-18 hours

4.      Toxic and explosive