MCB Ch. 10

Define Sepsis

microbial contamination

Define Asepsis

absence of significant contamination

Aseptic surgical techniques prevent…

microbial contamination of wounds

Define Sterilization

removing ALL microbial life

ex. pressurized steam

Define Commercial sterilization

kills *Clostridium botulinum* endospores

Define Disinfection

removes pathogens

ex. bleach

Define Antisepsis

disinfection of living tissue

ex. iodine (betadine)

Define Degerming

removing microbes from a limited area

ex. handwashing with soap

Define sanitization

lowering microbial counts on eating utensils

ex. industrial strength cleaners containing quaternary ammonium compounds

Define Biocide/germicide

kills microbes

Define Bacteriostasis

inhibits. does not kill

The effectiveness of treatment depends on…

* # of microbes
* environment (organic matter, temperature, biofilms)
* time of exposure
* microbial characteristics

How do Microbial Control Agents work?

* Cell Wall
* damage
* digest it
* block its synthesis
* Cell Membrane
* change permeability of membrane: injurious chemicals can enter cell, important ions exit cell
* Cellular Synthesis
* interrupt protein synthesis.
* inhibit proteins needed for growth and metabolism
* damage nucleic acids (prevent multiplication)
* Proteins
* denature
* agents may attach to active sites of protein (enzyme inhibitors)

Physical methods of Microbial control

* radiation
* osmotic pressure
* dessication
* high pressure
* low temperature
* filtration
* dry heat
* pasteurization
* moist heat

What is better? Moist or Dry heat

Moist heat is better. It denatures proteins. It conducts heat better, making it feel hotter when less heat is required and it takes less time. Less energy is needed

One of the most common physical control methods is…

heat

At temps above the growth range,

* proteins and nucleic acids are destroyed
* water is removed

Define Thermal Death Point

lowest temp at which all cells in a culture are killed in TEN MINUTES. (temperature is the independent variable)

Define Thermal Death Time

time during which all cells in a culture are killed at a particular temperature.

Moist heat does what to proteins?

denatures it

Define Autoclave

steam under pressure

What does pasteurization do?

reduce spoilage organisms and pathogens

Pasteurization does not affect…

* thermoduric organisms (will survive)
* bacterial spores

High temperature short time pasteurization

72c for 15 sec. Milk will need to be refrigerated

Ultra-high temp pasteurization

140c for

Define Dry Heat Sterilization + examples

kills by oxidation

* dry heat
* flaming
* incineration
* hot-air sterilization

Filtration suppress microbial growth by…

removes microbes by passage of liquid through a screen-like material with pores small enough to retain microorganisms.

Low temperatures suppress microbial growth by…

\+ examples

lower microbial metabolic and growth rates. slows down spoilage

* refrigeration
* deep-freezing
* lyophilization (freeze dry)

high pressure suppress microbial growth by…

denatures proteins

desiccation suppresses microbial growth by…

prevents metabolism (drying removes the water microbes need to live)

osmotic pressure suppresses microbial growth by…

causes plasmolysis

* salting causes water to diffuse out of organisms → dehydration and death

radiation suppresses microbial growth by…

affects cell metabolism and physiology.

* binds thymine together → prevent replication

Chemical agents are really good at sterilizing.

T or F?

False. They rarely achieve sterilization. But they do DISINFECT

Factors that affect the Germicidal activity of Chemicals

* nature of the microorg being treated
* nature of the material being treated (skin, porous, smooth, metal etc.)
* degree of contamination
* time of exposure
* strength of chemical action of the germicide

A higher concentration of germicide is always better. T or F?

False. You want the lowest, effective concentration.

Disk-Diffusion methods show what?

They show what chemical or concentration of chemical will be most effective

What does chlorine do?

keep bacterial populations low in municipal water supplies and swimming pools

What does Iodine do?

disinfect wounds, water, and restaurant equipment

What does Phenol and Phenolic Compounds do?

denature proteins

What metals can interfere with microbial metabolism? How?

These are all reactive with proteins

* Mercury
* Copper
* algicide
* antimicrobial
* Silver
* antimicrobial
* silver nitrate → prevent gonorrheal ophthalmia neonatorum
* silver sulfadiazine → topical cream on burns

How does Alcohol affect microbes?

Alcohol denatures proteins and disrupts membranes

Ethanol is disruptive against vegetative cells but not endospores? T or F?

True

Lipid dissolution causes what?

membrane disruption

How does soap remove microbes?

emulsify and solubilize particles on the skin

Detergents are …

Surfactants

Detergents can cause…

cytoplasm leakage from microbial membranes.

* react with cell membrane

List chemical food preservatives

* organic acids
* nitrite
* antibiotics

Organic acids can do what? + examples

control mold and bacteria in food and cosmetics

ex. sorbic acid, benzoic acid, calcium propionate

Nitrite does what?

prevents endospore germination

Antibiotics can do what as a food preservative?

Nisin and Natamycin prevents spoilage of cheese

List some examples of chemicals used in medical settings for ANTISEPSIS and DISINFECTION

antisepsis: isopropyl alcohol, iodine (betadine),

Disinfection: Chlorine bleach, glutaraldehyde

List some examples of chemicals used in household settings for ANTISEPSIS and DISINFECTION

antisepsis: isopropyl alcohol, hydrogen peroxide, boric acid

Disinfection: Chlorine bleach, phenols

What are some PHYSICAL methods used to sterilize or sanitize in a medical setting or in the food industry?

Sterilization: Autoclave, chemicals, radiation

Sanitization: detergents containing phosphates, industrial-strength cleaners containing quaternary ammonium compounds