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Flashcards in Chapter 5 & 20 Deck (52):
1

Sterilization

Process of destroying all microorganisms or viruses within or on a product (including endospores and fungal spores); no varying degrees

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Disinfection

A process that reduces the number of microorganisms or viruses within or on a product until they no longer represent a hazard

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Disinfectant

A chemical agent used to disinfect inanimate objects

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Antiseptic

A disinfectant that is nontoxic enough to use on human cells

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Types of Disinfectants

- cide: treatments that kill
- static: treatments that inhibit rather than kill
- e.g., germicide, fungicide, viricide, bacteriostatic/fungistatic agents

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Bacteriocide

Used to kill vegetative forms of bacteria, but not usually endospores

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Bacteriostatic or Fungistatic Agents

A chemical or conditions that prevent the growth of these organisms, but does not kill them

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Decontamination

Involves the inactivation and removal of both microbes and any toxins that may be present within or on the product

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Sanitation

In the food industry, decontamination on an area or product to meet public health standards

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Factors Affection Disinfectant Action

- Time of contact: death is not always instantaneous (may take hours)
- Temperature; usually work better at high temps but most are designed to work near room temp
- pH: work best at certain value (will vary)
- Number of microorganisms: greater number of cells, greater amount of time needed
- Presence of Extraneous Matter: organic matter may react and cause them to be less effective (soil, blood, pus, etc.)
- Concentration: in most cases, the more concentrated the shorter the killing time

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Decimal Reduction Time (D time)

The time it takes to kill 90% of bacteria present; usually constant over time - if it takes two minutes to kill 90% of a bacteria population, then a population of 100 would be reduced to 10 in two minutes and one in four

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Types of Microorganisms

- Least resistance: vegetative forms of most bacteria and viruses with membranes
- Moderate resistance: Mycobacterium tuberculosis, Staphylococcus aureus, and Pseudononas species, viruses with no membranes
- Highest resistance: bacterial endospores

Cells in the stationary growth phase are more resistant than cells that are actively growing.

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Effectiveness of Destroying Microbes

- High: Kill all organisms, including endospores; surface will be sterilized
- Intermediate: Kill resistant pathogens (mycobacterium tuberculosis) and non-enveloped viruses
- Low: Kill vegetative bacteria and enveloped viruses

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Antimicrobial Chemotherapy

The use of drugs to destroy or inhibit the growth of microorganisms that are causing disease

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Antibiotics

A chemical produced naturally by a microorganism (usually other bacteria or molds) that have antimicrobial effects; e.g., Streptomyces griseus (soil bacteria) are used to create streptomycin

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Synthetic Agents

Chemicals that have antimicrobial effects, but are produced in a laboratory (e.g., sulfa)

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Antimicrobic

A word that incorporates all types of antimicrobial drugs, regardless of origin

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High Selective Toxicity

An ideal characteristic of chemotherapeutic agents; the chemical is toxic to the microbe causing the disease, but much less so to the cells of the host (all chemicals are at least slightly toxic to a host - therapeutic index is used)

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Therapeutic Index

Ratio of the minimum dosage that is toxic to the host to the minimum dosage that is toxic to the microbe (MIC); e.g., 500mg/hr is toxic to humans while only 50mg/hr is toxic to bacteria - the ratio is 500/50 10:1

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MIC (Minimum Inhibitory Concentration)

The lowest dose that prevents the growth of a microbe

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Broad Spectrum

Toxic to a wide range of different species of pathogens, usually effective against both gram+ and gram- bacteria; low TI generally

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Narrow Spectrum

Toxic to only a few types of pathogens but fewer side effects; higher TI generally

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Characteristics of Ideal Chemotherapeutic Agents

- High selective toxicity
- Does not induce the development of resistant strains
- Will not cause hypersensitivity to the host (creating an immune response by the host - allergic reaction)
- Does not interfere with the hosts own defense mechanisms

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Targets of Antimicrobial Drugs

- Cell wall synthesis (High TI)
- DNA replication (Low TI)
- Transcription (Low TI)
- Protein Synthesis (Medium TI)
- Cell membrane function (Very low TI)
- Metabolic pathways (High TI)

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Mode of Action

The adverse effect on a microorganism; how the cell is killed

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Tincture

Combination of iodine with alcohol

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Iodophors

Combination of iodine and detergent

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Sulfonamides (synthetic)

Drugs that interfere with a unique metabolic pathway:
- Mode of Action: function as competitive inhibitors in a chemical pathway (broad spectrum)
- Toxicity: nearly harmless to humans, as folic acid is not produced in our bodies (High TI); there are some allergic reactions
- Current Effectiveness: most bacteria are resistant to the effects, as the drugs have been used extensively since the 1930s; can still be effective at high levels which can only be obtained in the urinary tract

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Folic Acid

Used in many important metabolic pathways; it is a component of an enzyme that is used to synthesize certain nucleic and amino acids; humans must consume in order for metabolic reactions to occur

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Penicillins and Cephalosporins

Drugs that disrupt cell wall synthesis:
- Mode of Action: Interferes with bacterial wall synthesis; cross linkages are prevented from forming in the the cell wall (in growing cells only,) creating a cell wall that is not capable of standing against the osmotic pressures generated within the cell (will lyse)
- Toxicity: very little; since humans do not have cell walls, these drugs do not cause many side effects; a portion of the population is allergic to them, and treatment may lead to death in some severe reactions; still drug of choice due to high TI
- Current Effectiveness: usually more effective against gram+ bacteria; has a hard time penetrating the outer membrane of gram- bacteria (many are narrow spectrum, some are broad)

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Glycopeptides (Vancomycin)

Drugs that disrupt cell wall synthesis; must be injected because it is poorly absorbed into blood stream:
- Mode of Action: inhibits the synthesis of peptidoglycan, no cell wall constructed
- Toxicity: few; nausea, hearing loss; high TI
- Current Effectiveness: narrow spectrum; gram+ only; little resistance, but some strains of S. aureus and Enterobacteria (within the colon) are resistant

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Aminoglycosides (Streptomycin, Gentamicin)

Drugs that interfere with protein synthesis:
- Mode of Action: attach to the 30S subunit of bacterial ribosomes, interfering with translation; mRNA is misread and proteins are incorrectly assembled
- Toxicity: severe, even though drug is not actively transported into eukaryotic cells; usually used in low doses and patient closely monitored for side effects, including damage to the kidneys and inner ear; low TI
- Current Effectiveness: broad spectrum, but used rarely as many bacteria are resistant; often used in conjunction with other antibiotics

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Tetracycline (Tetracycline, Doxycycline, Oxytetracycline)

Drugs that interfere with protein synthesis; drug of choice to treat undiagnosed disease (secondary bacterial infections):
- Mode of Action: attach to the 30S subunit of bacterial ribosomes, preventing the attachment of tRNA; protein synthesis completely blocked
- Toxicity: severe; nausea, diarrhea, extreme sensitivity to light; also caused liver and kidney damage, staining of teeth in children of early pregnant mothers, and can lead to secondary infections; low TI
- Current Effectiveness: very broad spectrum, but resistance is more common

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Secondary Infection

Infection that occurs along with or immediately following another infection, usually as a result of the first infection; antibiotics may suppress normal flora to such an extent that pathogenic organisms can easily establish themselves and cause disease; especially true with broad spectrum antibiotics

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Macrolides (Erythromycin, Azithromycin)

Drugs that interfere with protein synthesis; often used when patient is allergic to penicillin:
- Mode of Action: prevents protein synthesis by binding to the 50S subunit
- Toxicity: little; gastric distress, reversible liver damage
- Current Effectiveness: narrow spectrum (gram+ and mycoplasma); gram- often resistant as cell wall is an effective barrier

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Fungicides

Kill fungi; fewer drugs exist because it is harder to find unique cellular targets; generally have low TI and high toxicity; most used as topicals but a few can be taken orally or by IV; often the patient must remain in the hospital as treatment is occurring

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Polyenes

Fungicide that disrupts fungal cell membranes resulting in cytoplasmic leakage (itching, gastrointestinal disturbance - kidney damage, anemia, respectively); IV drip, topical; Amphoterican B most commonly used

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Flucytosine (Oral)

Fungicide that inhibits nucleic acid synthesis (rash, diarrhea, liver damage)

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Antiviral Compounds

Drugs that prevent transcription and translation, or the maturation of viruses; typically have a low TI and are very toxic, with a number of side effects; no drub provides a cure but used to slow progression of the disease and treat symptoms

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Acycolvir

Antiviral compound that inhibits viral DNA polymerase in the herpes virus; few side effects as the drug is only activated in cells that have the virus; either used as topical or by IV to prevent recurrent herpes out-breaks

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Nucleotide Analogs (AZT, ddl, ddC)

Molecules with a similar, but not exact, molecular structure to four normal types of nucleotides; this molecule (drug) is then mistakenly incorporated into the DNA strand of growing viruses, but the strand is useless; DNA replication eventually halts

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Amantadine & Rimantadine

Antiviral compounds that prevent the uncoating of the influenza virus; help alleviate symptoms; must be given in the early stages of infection

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Drug Cocktails

The use of 3-4 different antiviral compounds to stop and reverse the progress of the AIDS virus; as of yet, not a cure, even though people on treatment return to normal lives and have no visible traces of the virus; if treatment ends the virus returns

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Considerations for Choosing Antimicrobial Drugs When Treating Infections

- Always choose a drug with the highest TI that is effective against the specific microbe causing the infection
- Choose a drug that will not interact with any other medications/herbs that the patient is taking
- Choose a drug that can easily diffuse into the body cavities that are infected
- A mode of delivery must be determined that is most effective and most beneficial to the patient (IV drip, injection, oral)
- Kidney/Liver condition must be assessed
- If treatment is successful, then a drug or a new combination of drugs may be necessary in order to treat the disease

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Antagonistic Drugs

Two drugs make each other less effective

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Synergistic Drugs

Two drugs are more effective when taken together

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Additive Drugs

No drug interaction; neither antagonistic or synergistic

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Innate Resistance

If a bacteria naturally lacks a drug's cell target, then it cannot be affected by the drug (e.g., Mycoplasma has no cell wall and therefore is innately resistant to penicillin)

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Development of Bacterial Resistance to Antibiotics

- Innate resistance
- Bacteria acquire most resistance through mutation or genetic exchange (conjugation/R plasmid)
- Bacteria modify cellular target
- Bacteria are able to destroy or inactivate drug
- Bacteria prevent drug from entering the cytoplasm by altering membrane permeability
- If drug is an enzyme inhibitor, the bacteria can produce very large amounts of the enzyme so that the metabolic pathway is never fully inhibited

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Hypersensitivities (allergies)

The body recognizes an antibiotic as a foreign substance and reacts against it; fever, rash, and anaphylactic shock, which may be life threatening

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Toxicity

Drug may cause permanent damage to a patient; antibiotics that have low TIs can be especially harmful

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Production of Resistant Strains

The more antibiotics are used, the better opportunity that an organism will develop resistance to it