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Physical Agents for Microbial Control
i.e. heat or radiation
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Chemical Agents for Microbial Control
i.e. disinfectants and antiseptics
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Highest Resistance to Microbial Control
- Prions
- Bacterial Endospores
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Moderate Resistance to Microbial Control
- Protozoan Cysts
- Naked viruses
- Hep B
- Polovirus
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Least Resistance to Microbial Control
- Fungal Spores
- Enveloped Viruses
- Yeasts
- Protozoan Trophozoites
- BacterialVegetative Spores
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Bacterial Endospores
- Most resistant to control
- 18x's harder to destroy than counter part vegetative cells
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Sterilization
- Removes ALL viable microorganisms including viruses
- For inanimate objects
- Usually heat but also some chemicals called sterilants
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Microbicidal
Kills microbes
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Microbistasis
Stops reproduction of microbes
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Disinfection
- Physical or chemical agent to destroy vegetative pathogens but NOT bacterial endospores
- On inanimate objects
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Microbial Load
Microbial Population
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Sanitazation
- Removes debris, microorganisms and toxins
- Reduces infection and spoilage
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Sanitization > Sterilization
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Degermation
- Reduction of microbial load through mechanical means on living tissue
- Surgical hand soap, alcohol wipes
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Microbial Agent
- Targets metabolic process in a cell
- Time & Concentration
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Active cells die more quickly than older
More metabolic activity vs. less
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Effectiveness of agent governed by:
- 1) # of microorganisms (more contaminants, longer to destroy)
- 2) Nature of microorganisms in population (more variation, higher resistance)
- 3) Temp of pH in environment
- 4) Concentration (dosage, intensity) of agent
- 5) Mode of action (kill or inhibit)
- 6) Presence of solvents, interfering organic matter and inhibitors (i.e. blood, saliva, feces)
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Cellular targets of physical & chemical agents
- 1) cell wall (block synthesis, digest it, breaks down surface)
- 2) cel membrane (disrupts 2 way communication when disrupted. cannot prevent loss of molecules nor bar entry of danger)
- 3) cellular processes (Inhibits formation and proteins required for growth)
- 4) Protein Function (Breaks down native state bonds)
- 4) proteins
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Temperatures that exceeds maximum growth temperature:
Micrbicidal
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Temperatures lower than minimum growth temperature:
Microbistatic
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Moist Heat
- Hot water, boiling water, steam
- 60 to 135 c
- Lower temps and shorter exposure
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Dry Heat
- air w/ low moisture content that has been heated
- 160 c
- higher heat and longer exposure protein
- Dehydrates cell
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Thermal Death Time
TDT
Shortest length of time required to kill all test microbes at a specified temperature
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Thermal Death Point
TDP
Lowest temperature required to kill all microbes in a sample in 10 minutes
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Common methods of moist heat control
- 1) Steam under pressure (15psi, 121c, most efficient, autoclave)
- 2) Nonpressurized steam (treatment, incubation, treatment. intermittent sterilization. for heat sensitive culture)
- 3) Boiling water (disinfection only, easily recontaminated, good for non sporeforming pathogens)
- 4) Pasteurization (disinfection of beverages. 71.6 for 15 sec *Flash*, or 63-66 for 30 *Batch*)
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Incineration
- Dry Heat
- 800-6,500 c
- Reduces microbes to ashes and gas
- Metals and heat-resistant glass materials
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Dry oven
- Usually electric
- 12 min to 4 hours
- 150c-180c
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Radiation
- Energy emitted from atomic activities and dispersed at high velocity
- gamma, x, ultraviolet
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Irradiation
- Bombardment with radiation at cellular level
- Absence of heat- thus cold/ low temp sterilization
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Ionizing Radiation
- Penetrates solid barrier
- Bombards cell
- Breaks DNA and mutates
- gamma, x, high speed electrons
- Food and anthrax
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Non Ionizing Radiation
- Enters cells
- Strikes molecules
- Effects DNA through abnormal bonds
- Ultraviolet radiation
- Disinfection
- Hospitals, schools, food prep, drinking water, purifying liquids
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High Level Chemical Agents
Kills Endospores and are sterilant
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Intermediate Level Chemical Agents
Kill fungal spores and resistant pathogens
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Low Level Chemical Agents
Kills vegetative bacteria, fungal cells and some viruses
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Halogens in Chemical Agents
- Group VII
- Exert microbicidal in nonionic state
- Active ingredient in 1/3 of antimicrobial chemical
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Hypochlorites
- Halogen
- Extensively used
- Sanitization & disinfection of food equipment, pools, spas, water, fresh foods
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Iodine
- Halogens
- Pungent blue/black chemical that forms brown colored solution
- Disinfects inanimate objects and treatment for burned/ infected skin
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Iodophors
Used to prepare skin & mucas membrane
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Phenolics
- strongly microbicidal but not reliably sporicidal
- toxic- cannot be used as antispetics
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Applications of Phenolics
- general disinfection of drains, cesspools and animal quarters
- not a medical germicide
- lysol, soaps, antibacterial product in household products
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Chlorohexidine
- 2 Phenolic rings
- Bactericidal for gram negative and positive
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Alcohols as antimicrobial agent
- colorless hydrocarbons
- ethyl and isopropyl suitable for microbial control
- various impacts dependig on concentration
- lower concentration is greater killing
- 100% is only inhibitor
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Applications of alcohols
- germicidal
- nonirritating
- inexpensive
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Hydrogen Peroxide
- colorless, caustic liquid that decomposes in presence of light, metals
- Applications: antispetic for wounds,
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Detergents
- Poloar molecules that act as surfactants
- limited mocrbicidal power
- soaps
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Heavy metal Compounds
- mercury, silver, gold, copper, arsenic, zinc
- applied in microbial control over several centuries
- high atomic weight
- antimocrobial effects in exceedingly small amounts (oligodynamic)
- Brings metabolism to a sand still
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Aldehydes as Germicides
- CHO functioning group on terminal carbon
- glutaraldehyde
- formaldehyde
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Antimicrobial Therapy Involves:
- 1) Microbes Sensitivity
- 2) Drug's toxicity
- 3) Health of patient
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Selectively Toxic
- Drugs should kill or inhibit the growth of microbes with out simultanously damaging host tissue.
- Best block synthesis of the cell wall
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Targets in an Actively Dividing Cells
- 1) Inhibition of cell wall synthesis
- 2) Breakdown of cell membrane structure or function
- 3) Inhibition of structures and functions of DNA & RNA
- 4) Inhibition of protein synthesis
- 5) Blocks key metabolic pathways
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Drugs spectrum
Particular range of activity
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Narrow Spectrum
- Effective on small range of cell types
- Gram + only
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Medium-Spectrum
Effective on both G+ and G- but not all of them
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Broad Spectrum
- Works on G+ and G-
- Attachs ribosomes that are found in most pathogens
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Inhibition of Cell Wall Synthesis
- Considered bactericidal
- Active in young cells becous of active matabolism
- Penicillins & Cephalosporins
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Breakdown of cell membrane structure or function
- Damaged membrane = death from disruption in metabolism or lysis
- Do not have to be actively dividing to be destroyed
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Inhibition of structures and functions of DNA & RNA
- Inhibits replication by stopping transcription
- Blocks replication of viruses
- AZT and Acyclovir
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Inhibition of protein synthesis
- Ribosome mRNA complex
- Misreading of mRNA leads to abnormal proteins
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Blocks key metabolic pathways
Drugs mimic substrate and enters into competitive inhibition
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How penicillan works
- Cells continue to divide but without a cell wall
- Shape is distorted eventually after division membrane ruptures and eliminates themselves
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Chemotherapy
Looks for enzymes to shut down
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Half Life
How long until all substructures are gone?
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Isotopes in Half Life
- Stability rate changes
- Los of core energy
- Nucleus changes and decays
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