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Define: sterilization, disinfection, antisepsis, asepsis, ____cidal, ____static
- Sterilization: Removal of microbial life
- Disinfection: Removal of pathogens from inanimate objects
- Antisepsis: Removal of pathogens from living tissue
- Asepsis: The absence of significant contamination
- ___-cidal: kill microbes
- ___-static: inhibit growth of microbes
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Physical methods of microbial control and how they suppress microbial growth [very in depth]
- Heat: kills by denaturing bacterial enzymes.
- Moist heat: kills by denaturing proteins
- 1. Boiling kills vegetative forms of bacteria
- 2. Autoclaving (steam under pressure) kills endospores
- 3. Pasteurization uses quick heat or long medium heat to reduce spoilage organisms and pathogens
- Dry heat: kills by oxidation
- 1. Incineration of biohazardous materials
- 2. Flaming incoluation loops in lab
- 3. Hot-air sterilization
- II. Filtration: removes microbes
- 1. Gases/air use mask/filters
- 2. Liquids use membrane filters
- III. Low temperature: only inhibits microbial growth
- 1. Refrigeration
- 2. Deep freezing
- 3. Lyophilization
- IV. High pressure: denatures proteins
- Kills vegetative cells, not spores
- V. Desiccation: removal of H2O prevents metabolism
- VI. Osmotic pressure: Causes lysis
- High salt or sugar (often in food preservation)
- VII. Radiation: kills bacteria by damaging the DNA
- 1. Ionizing radiation (X rays, gamma rays, electron beams)
- 2. Nonionizing radiation (UV, wavelength 260nm)
- 3. Microwaves kill by heat, not especially antimicrobial
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Types of heat-related sterilization abbreviations/meanings.
- TDP (thermal death point): Lowest temp to kill all cells in a culture in 10 minutes
- TDT (thermal death time): Minimal time to kill all cells in a culture at a given temperature
- DRT (decimal reduction time): Minutes to kill 90% of population at a given temperature
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List the different chemical methods of microbial control and describe how each suppresses microbial growth
- Phenolics: causes damage to plasma membrane (lysol)
- Bisphenols: inhibits formation of membranes(hexachlorophene, triclosan)
- Biguanides: Disrupt plasma membranes (chlorhexidine)
- Halogens: Alter protein synthesis and membranes (Iodine) strong oxidizing agent (Chlorine)
- Alcohols: denatures proteins, dissolve lipids eg membranes
- Heavy metals: denature proteins by combining with sulfhydryl groups (Ag, Hg, Cu)
- Surfactants: mechanical removal and reaction with bacterial membrane
- Quaternary ammonium compounds: denature proteins, disrupt plasma membranes
- Aldehydes: inactivates proteins by cross-linking with functional groups
- Peroxygens: oxidizing agents
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Explain how ionizing and non-ionizing radiation kills cells
- Ionizing radiation (X rays, gamma rays, electron beams): ionize water to generate free radicals that destroy DNA.
- Use for sterilization of instrumentations
- Nonionizing radiation (UV, wavelength 260nm): damage DNA by creating thymine dimers which inhibit DNA replication.
- UV light can damage eyes, cause burns, and skin cancer
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Explain how type of bacteria, physiological state of the bacterial cell, and environmental conditions affect the effectiveness of chemical control of microbial growth
- Type of bacteria: Gram pos/neg, biofilms, preferred temperature, aerobe/facultative anaerobe/etc,
- Physiological state of bacterial cell: osmotic state, replication state, availability of nutrients
- Environmental conditions: time exposed, material being disinfected,
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