micro ch 9

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cannon class, from power point notes

Antimicrobials that kill

germicides, bactericides, fungicides, virucides, sporicides

Antimicrobials that inhibit microbial growth/reproduction

microbistatic, bacteriostatic, fungalstatic, etc.

Disinfectant

Antimicrobial agent used to destory pathogenic nonsporulating bacteria or their toxins on inanimate objects. that is they are bactericidal.

germicide or microbicide

any chemical agent used to kill pathogenic organisms, some can be used (safely) on living tissue of they can be used on inanimates.

Antiseptic

antimicrobial agent that inhibits or kills infectious microbial growth in vivo. they tend to be more bacteriostatic than bactericidal & are sufficientlt non-toxic to allow application to skin & mucous membranes.

Sanitizer

a compound such as soap or detergent which is used to remove microbes and food.

Degermer

an agent of removing microbes from the human skin

Factors that affect Death rate

-number of microbes
-nature of microbes in the population
-temperature and PH of enviroments
-concentration or dosage of agent
-mode of action of the agent
-persence of solvents, organic matter, or inhibitors

Antimicrobial Agents' modes of action

1. the effects of agents on the cell wall
2. how agents affect the cell membrane: surfactants
3. agents affecting nucleic acid synthesis and protein synthesis
4. agents that alter protein function: denaturing
5. antimetabolites: inhibits the utilization of a metabolites necessary for growth

Methods of physical control

1. heat-moist and dry
2. cold temperatures
3. desiccation
4. radiation
5. filtration

Moist heat

lower temperatures and shorter exposure time; coagulation and denaturation and proteins

Dry heat

moderate to high temperatures; dehydration, alters protein structure; incinceration

TDT- Thermal death time

shortest length of time required to kill all test microbes at a specified temperature

TDP- Thermal death point

lowest temperature required to kill all microbes in a sample in 10 minutes

Pasteurization

heat is applied to kill potential agents of infection and spoilage without destroying the food flavor or value (batch/flash)

Microbiostatic

slows the growth of microbes; used to preserve food, media, and cultures

Dessication

gradual removal of water from cells, leads to metabolic inhibition

Lyophilization

freeze drying; preservation

Ionizing radiation

Deep penetrating power that has sufficient energy to cause electrons to leave their orbit, breaks DNA; gamma rays, X-rays, cathode rays; preserving food

Nonionizing radiation

Little penetrating power so it must be directly exposed; UV light creates pyrimidine dimers, which interfere with replication; sterilizing air, water or surfaces

Desirable qualities of chemicals

-rapid action in low concentration
-solubility in water or alcohol, stable
-broad spectrum, low toxicity
-penetrating
-noncorrosive and nonstaining
-affordable and readily available

High-level germicides

kill endospores; may be sterilants

Intermediate-level germicides

kill fungal spores (not endospores), tubercle bacillus, and viruses

Low-level germicides

eliminate only vegetative bacteria, vegetative fungal cells, and some viruses

Factors that affect germicidal activity of chemicals

-nature of the material being treated
-degree of contamination
-time of exposure
-strength and chemical action of the germicide

Chlorine, hypochlorites (chlorine bleach), chloramines

-Denatuate proteins by disrupting disulfide bonds
-intermediate level
-unstable in sunlight, inactivated by organic matter
-water, sewage, wastewater, inanimate objects

Iodine, iodophors (betadine)

-interferes with disulfide bonds of proteins
-intermediate level
-milder medical and dental degreming agents, disinfectants, ointments

Phenolics

-disrupt cell walls and membranes and precipiate proteins
-low to intermediate level
-bactericidal, fungicidal, virucidal, not sporicidal

Alcohols

-acts as surfactants dissolving membrane lipids and coagulating proteins of vegetative bacterial cells and fungi
-intermediate level

Hydrogen Peroxide

-produces highly reactive hydroxyl-free radicals that damage protein and DNA while also decomposing to 0(2) gas- toxic to anaerobes
-anticeptic at low concentrations; strong solutions are sporicidal

Aldehydes

-kill by alkylating protein and DNA
--glutaraldehyde and formaldehyde

Glutaraldehyde

2%(Cidex) used as sterilant for heat sensitive instruments
-high-level

Formaldehyde

disinfectant, preservative, toxicity limits use
-intermediate to high level

Gases and Aerosols

-Ethylene oxide
-strong alkylating agents
-high-level
-sterilize and disinfect plastics and prepackaged devices, foods

Quaternary Ammonia compounds (quats)

-acts as surfactants that alter membrane permeability of some bacteria and fungi
-very low-level
-effective against some gram(+) bacteria, most viruses, fungi, and algae
-ineffective against tuberculosis bacterium, bacillus, hepatitis virus, spores and any concentration, and gram(-) bacteria

Detergents and Soaps

mechanically remove soil and grease containing microbes

Heavy Metals

-solutions of silver and mercury kill vegetative cells in low concentrations by inactivating proteins
-oligodynamic action
-low-level
Merthiolate, silver, nitrate, silver

Dyes

-very active against gram(+) species od bacteria and various fungi
-sometimes used for antisepsis and wound treatment
-low-level
-narrow spectrum of activity

Acids and Alkalis

low level of activity
-organic-prevent spore germination and bacterial and fungal growth
-acetic-inhibits bacterial growth
-propinonic- retards molds
-lactic- prevents anaerobic bacterial growth
-benzoic and sorbic- inhibits yeast

High resistance

prions, bacterial endospores

Moderate resistance

pseudomonas sp., mycobacterium tuberculosis, staphylococcus aureus, protozean cysts

Least resistance

most bac. veg cells, fungal spores and hyphae, yeast, enveloped viruses, protozan trophzite

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