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56 Cards in this Set

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-used living tissue

-or on inert substance

-Reduction in the number of microorganisms and viruses, particularly potential pathogens, on living tissue


Refers to an environment or procedure free of pathogenic contaminants



a chemical that kills

-suffixes indicating destruction of a type of microbe " virocide, fungicide"


removal of microbes by mechanical means


-tion: not

destruction of most microorganisms and viruses on nonliving tissue

-safe enough for living tissue


Use of heat to destroy pathogens and reduce the number of spoilage microorganisms in foods and beverages


"restaurants" remove enough for safety

Removal of pathogens from objects to meet public health standards



bacteriostatic agent, does not kill; it prevents growth.

suffixes indicating inhibition, but not complete destruction, of a type of microbe.


killing ALL microbes off.

Destruction of all microorganisms and viruses in or on an object.

Factors affecting how long it takes to kill bacteria...

N E T - C

Number of microbes


Time of exposure

Characteristics of microbes

Environment :

slowed by organic materials, biofilms (e.g., feces, sewage)

hastened by prior cleaning, heat

Characteristics of microbes: most resistant are....

spores (ex: Clostridium difficile)

thick lipid coats

protozoan cysts

Microbial Sensitivity to Chemical Biocides



bacterial endospores


cysts of protozoa

active-stage protozoa (trophozoites)

most gram-negative bacteria


nonenveloped viruses

most gram-positive bacteria

enveloped viruses



Alteration of membrane permeability

poking holes in the membrane= spilling guts

-outsides go in; insides go out

Damage to proteins and nucleic acids

-if the proteins are damaged, they will most likely not work anymore

-some more critical than others

-cannot do work


-non-funcational proteins

-screws up DNA

Physical Control Methods

T - D O R


Desiccation; drying out

Osmotic pressure


Types of Temperature methods....

Heat preservation; pasteurization

Moist heat

Dry heat

Low heat

Heat Preservation

-Must know temp. and time needed to kill critical bacteria

-Thermal death time

-how long it takes to kill a certain bacteria at a certain temp


Used when taste of product would be damaged by longer heating

-lowers numbers of pathogens (63*C for 30 minutes)

typically pasteurized: milk, juice, yogurt and ice cream

-UHT: sterilization (140*C for 1-3 seconds)

--- product may lose some nutritional value

Moist Heat

Coagulates proteins by breaking hydrogen bonds (denatures)


-- 10 mins kills most pathogens

--Hepatitis virus nbeeds 30 minutes

-- spores need 20 hours!

Autoclave: 15 psi for 15 minutes at 121*C


-uses pressure and MOIST heat to kill microbes

-similar to rice cooker procedure


Dry Heat


-oven (170*C 2 hours)

-spores are resistant to dry heat!!!!

Low Temperature

-can preserve organisms

-refrigeration is bacteriostatic (does not kill; prevents growth)

---most pathogens do not grow

---Listeria spp. are psycrotolerant


---slow freezing creates ice crystals * that can sheer cell membranes causing cell death when they thaw***

---ice in the membrane can shatter it

(95% ethynol and dry ice- freezing pathogens)

Membrane Filtration

-Pore SIZE controls which microbes are removed

--filter sterilization with 0.2 micrometers

-HEPA filters used in safety hoods and operating theaters

Limiting Water

Desiccation: bacteriostatic (does not kill pathogens; prevents growth)

--Lyophilization: used to preserve cultures** used as freeze drying to preserve organisms**

-Osmotic pressure- high concentrations of salt and sugar

-Molds and yeasts most resistant

Radiation:** WONDERFUL WAY of killing **

Ionizing Radiation...

gamma rays, X rays, high energy electron beams - most energetic

- ionization of H2O to form OH- radicals

-Cause mutations in DNA and death

Low level ionizing radiation....

-used on spices, certain meats and vegetables

-high energy electron beams used for medical supplies

UV Radiation

-Thymine dimers in DNA

-Germicidal lamps, vaccine disinfection

-Not penetrating

-Can damage eyes

**** UV Radiation; T's will bind to themselves instead of A's; during replication this causes mistakes.****


-very little effect on some microbes

-microwave oven kill vegetative pathogens by heating

-solid foods heat unevenly

**** place a bowl of H2O in microwave-steam destroys microbes***

Chemical Methods




-Surface-active agents (surfactants)

-Chemical food preservatives

-Aldehydes (formaldehyde = formalin)

-Gas sterilization

-Oxidizing agents




--damage lipid membranes

--active in presence of organic matter


--persist for long periods after application

--example - Dettol


originally used by Joseph Lister, as carbolic acid vapors during surgery

** some phenols can be used as antiseptics****



-Hexachlopophene (pHisoHex) and triclosan (mouthwash)

-Antibacterial soaps and toothpaste

-Broad spectrum of activity



--Chlorhexidine (wonderful antiseptic)

--low toxicity

--used on skin and mucous membranes

--surgical scrub in veterinary hospitals

Disinfectants/ antiseptics

-Halogens*** used a lot, and wonderful to clean wounds, cuts-does not burn used with...


---used in solution

---Betadine and Isodine


---gas that forms bleach (hypochlorite) in water

---destroys cell walls and enzymes (coagulates proteins and enzymes)



--protein denaturation and membrane damage

-evaporate quickly

---good and bad **90 seconds to really kill all microbes** one alcohol swipe before a prick won't kill off much from skin***

-Ethanol and isopropanol most common

-100% alcohol is not good as denaturing proteins requires water molecules

Evaluation of Disinfectants/antiseptics


-closer to disk= higher concentration of chemical

-one chemical is not sufficient for everything

Heavy Metals as Disinfectants

-denature proteins

Silver Nitrate

(topical cream)

Mercuric Chloride (paint)

- **red paint on wounds; pretty toxic--- used to be used as an antiseptic---poisonous---was used to treat syphilis

Copper Sulfate


** burn creams**

Zinc ( mouthwash, paints)

antibacterial effects


Decrease surface tension

damage lipid membranes

** attracted to membranes-- distrupts them. Insert themselves inside but not evenly.

** soaps and detergents

---quaternary ammonium compounds: microbial

Quaternary Ammonium Compounds ( Quats)

Ammonium ions

Benzalkonium chloride

Chemical Food Preservatives

Sodium benzoate

Sorbic acid

Calcium propionate

Sodium nitrate and sodium nitrite

Sodium benzoate

In acidic foods

reduces pH to 5 or lower which inactivates phosphofructokinase

Sorbic acid

weak acids

inhibit enzymes

Calcium propionate

used in breads

non-toxic, but inhibits growth

Sodium nitrate and sodium nitrite

Inhibits Clostridium botulinum



Formaldehyde (formalin) and glutaraldehyde

-used to disinfect instruments

-used to preserve tissues for pathology

-irreversibly cross-linked protein molecules

Gas Sterilization

Put into a chamber where ethylene oxide is pumped inside to sterilize

Ethylene oxide

-denatures proteins

-kills all spores and microbes with lengthy exposure

-high penetration

-for use when sensitive to heat or moisture

Oxidizing Agents



Hydrogen peroxide *really toxic;bubbling*

Benzoyl peroxide

Practice acid

--interfere with metabolism (especially of anaerobes)

Antiseptic Effectiveness:

Soap and Water

does not kill bacteria! can have an affect with out killing microbes though...

Chemical Effectiveness

you must leave the chemical on for the appropriate time to be effective