Controlling Microbes Flashcards by Christina Stafstrom

detergents act as

wetting agents and emulsifiers

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is the single most important step to achieving control

hand washing

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hospital acquired infections

nosocomial infections

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what is most common and most reliable mechanism in regards to food/ production

heat treatment

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agent which kill microbes

-cide

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kill microorganisms and viruses, but not

necessarily endospores

germicide

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agent which prevents microbial growth

-static

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the complete removal or destruction of all microbes

Even spores and viruses are removed

sterilization

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Killing C. botulinum endospores

commercial sterilization

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the killing, inhibition or removal of most disease causing
microbes
Also reduces the total microbial population

disinfection

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agents, generally chemical, used on inanimate

objects

disinfectants

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form of disinfection designed to prevent infection

by microorganisms in/on living tissue

Antisepsis

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chemical agents that kill or inhibit

growth of microorganisms when applied to tissue

Antiseptics

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substantial reduction of microbial population

to levels that meet accepted public health standards

sanitation

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treatment to reduce microbes to a level considered safe

decontamination

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removal of microbes from a surface by

mechanical means

Degerming

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what are the conditions affecting the effectiveness of antimicrobial activity

What microorganisms are present
Amount of contamination
Concentration or intensity of an antimicrobial agent
Duration of exposure
Temperature
Local environment
Composition of the item

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how do microbes die

Microbes are not killed instantly
Microbes are considered to be dead
when they are unable to reproduce in
conditions that normally support their
reproduction

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usually enhance the effectiveness of an agent

higher temperatures

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what do physical methods of control include

Mechanical removal
Filtration
Drying (reducing water availability)
Heat
Irradiation

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Reduces microbial population or sterilizes
solutions of heat-sensitive materials by
removing microorganisms
Also used to reduce microbial populations in air
Often used in conjunction with other methods

filtration

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what are the two main types of filtration

depth and membrane filters

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Thick fibrous or granular filters that remove microorganisms by physical screening, entrapment, and/or adsorption

depth filters

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Porous membranes with defined pore sizes that remove

microorganisms primarily by physical screening

membrane filters

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(freeze drying) | Widely used to preserve foods

Lyophilization

Typically the most cost effective method | Relatively fast, reliable, safe and inexpensive

heat

two types of heat control

dry and moist

Effective against all types of microorganisms | Degrades nucleic acids, denatures proteins, and disrupts membranes

moist heat

Destroys most microorganisms and viruses Does not destroy endospores Not effective means of sterilization

boiling

developed to avoid spoilage of wine Controlled heating at temperatures well below boiling Does not sterilize but significantly reduces organisms Used to increase shelf life of food

Pasteurization

Preferred method of sterilization

Pressurized steam

why is dry heat not as effective as moist heat

Sterilization with dry heat requires longer times and higher temperatures

method of dry heat sterilization Oxidizes cell to ashes Used to destroy medical waste and animal carcasses

incineration

stops microbial reproduction due to lack of liquid water some microorganisms killed by ice crystal disruption of cell membranes Kills up to 50% of microbes

freezing

Low temperatures slow down or stop enzymatic reactions -- slowing microbial growth and reproduction

refrigeration

what does a shorter wavelength mean

higher frequency and more energy

this can be ionizing or non-ionizing

radiation

Non-ionizing radiation Damages DNA causing thymine dimers Generates free radicals

ultraviolet radiation

Includes Gamma radiation, X-rays Radiation able to strip electrons from atoms (forms ions) Penetrates deep into objects Causes damage to DNA and proteins

ionizing radiation

what are Chemical Agents of Control

Disinfectants Antiseptics Antibiotics

conditions influencing antimicrobial effectivness

highly effective, Activity in presence of organic material, Compatibility with material being treated, toxicity, residue, storage, cost/availability, environmental risk

Phenolics

cresols

Bisphenols

triclosan

alcohols

– isopropyl, ethanol

peroxides

hydrogen peroxide

halogens

iodine, chlorine

heavy metals

silver, copper

detergents

anionic, cationic

sterilizing gases

ethylene oxide, ozone

who were phenolics first used by

Lister in 1870

what do phenolics do

Act by denaturing proteins and disrupting cell membranes effective in presence of organic material and long lasting Commonly used as laboratory and hospital disinfectants

what percent isopropyl or ethyl alcohol | kill vegetative bacteria and fungi

60-80%

Coagulates proteins and essential enzymes and damages lipid membranes Commonly used as antiseptic and disinfectant

alcohols

what are the limitations to alcohol

Evaporates quickly, limiting contact time May damage material such as rubber and some plastics

Powerful oxidizing agent Effectiveness depends on surface being treated Readily biodegradable

hydrogen peroxide

is hydrogen peroxide more effective on living tissue or inanimate objects

inanimate objects

Used as a skin antiseptic in tincture or iodophore Kills vegetative cells but not reliable with endospores

iodine

alcoholic solution

tincture

carrier molecule

iodophore

Oxidizing proteins and other cell components | common disinfectant

halogens-iodine

Important disinfectant Caustic to skin and mucous membranes Destroys vegetative bacteria and fungi, but not spores

halogens-chlorine

combine with enzymes and proteins interfering with function High concentrations are toxic to human tissue

heavy metal compounds

Organic molecules with hydrophilic and hydrophobic ends Act as wetting agents and emulsifiers facilitating mechanical removal of organisms Not disinfectant

detergents

Quaternary ammonium compounds Are effective disinfectants Positive charge attracted to negatively charged cells, reacting with the membrane

cationic detergents