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30 Cards in this Set
- Front
- Back
microbial death defn:
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irreversible loss of the ability to divide - probability of any one cell dying is constant per unit of time
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bacteriocidal defn:
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describes a compound/drug that kills bacteria
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bacteriostatic defn:
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describes a compound/drug that inhibits growth of bacteria
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sterilization defn
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the complete killing or removal of all living microbes from a growth medium
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disenfectant defn
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a chemical agent which causes death of microbes and reduces numbers, but does not produce a sterile environment
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biocide/germicide defn:
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refers to chemical agents that kill microbes
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sanitizers defn:
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only reduce the numbers of microbes on inanimate surfaces
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detergents defn:
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disperse and remove soil and organic material from surfaces and permit disenfectants to act
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thermal death point defn:
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the lowest temperature at which a 10 min exposure of a given volume of a broth culture results in sterilization
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To kill a bacterial cell:
cause irreparable damage to its: (3) |
1) genome
2) envelope (g+ cell membrane or g- inner membrane and outer membrane) 3) inactivate/denature certain classes of proteins =catabolic enzymes --> no energy = biosynthetic enzymes --> no macromolecules = structural proteins --> eg membrane |
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Disenfection goal:
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to reduce numbers, not produce a sterile environment
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Chemotherapy goal:
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kill all microbes
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Selective toxicity related to:
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5 chemotherapy mechanisms with high to low selective toxicity
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Death Kinetics General Principles (3)
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1) Fraction of microbes die during given interval
2) time to sterility depends on initial numbers 3) bacteria and viruses vary in susceptibility (g+ vs. g-, spores vs. vegetative cells) |
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Death Kinetics:
Environmental conditions determine: |
Death Kinetics:
Environmental conditions determine: effectiveness of disenfectants |
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Control of Microbial Growth
Protein Denaturation moist heat (3 examples) |
1) boiling 100C 5-10min except spore formers
2) autoclave/pressure cooker 121C 2-3min vegetative 15 spore 3) flash pasteurization 71C 15sec |
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Control of Microbial Growth
Protein denaturation dry heat temp: time: used for: |
Control of Microbial Growth
Protein denaturation dry heat temp: 160-170C time:1-2hrs used for:glassware and metal objects |
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Control of Microbial Growth
Protein denaturation Chemicals effectiveness depends on (3): Mechanisms (2): |
Control of Microbial Growth
Protein denaturation Chemicals effectiveness depends on (3): 1) concentration 2) time 3) temperature Mechanisms (2): 1) disrupt protein water interactions with more protein protein interaction (aggregation and denaturation) 2) disrupt protein-lipid interaction (non-functional membrane) |
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Mechanisms of Chemical Disenfectants (5 mechanisms, 3 substances)
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Mechanisms of Chemical Disenfectants (5 mechanisms)
1) denature proteins (alcohol) 2) denature proteins and bind phospholipids 3) denature proteins and lipids 4) denature lipids (alcohol) 5) alter membrane permeability (phenols) |
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Control of Microbial Growth
Phenol First used: Importance to other disenfectants: Common example: |
Control of Microbial Growth
Phenol First used: antiseptic in surgery Importance to other disenfectants: all compared to phenol ith phenol coefficient (PC) Common example: Lysol |
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Calculate PC
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Cpd a kills bacteria in 10 min dillution 1:450
phenol kills bacteria in 10 min dillution 1:90 PC = 450/90 = 5 |
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Meaning of PC
PC > 1 PC = 1 PC < 1 |
Meaning of PC
PC > 1: more effective disenfectant PC = 1: equally disenfectant PC < 1: less effective |
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Control of Microbial Growth
Disruption of Cell Membrane Which 2 types of detergents? |
Control of Microbial Growth
Disruption of Cell Membrane Which 2 types of detergents? 1) cationic detergents 2) anionic detergents |
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Control of Microbial Growth
Disruption of Cell Membrane Cationic detergents works because: group of compounds: -mechanism: -works against: -example: |
Control of Microbial Growth
Disruption of Cell Membrane Cationic detergents works because: positive charge of detergent attracts negative charge on microbial cell surface group of compounds: quaternary cpds e.g. benzylalkaonium chloride -mechanism: some detergent action with disenfectant activity -works against: most microbes, not spores -example: Roccal D |
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Control of Microbial Growth
Disruption of Cell Membrane Anionic detergents effectiveness vs. cationic: example: |
Control of Microbial Growth
Disruption of Cell Membrane Anionic detergents effectiveness vs. cationic: less due to negative charge on microbial cell surface example: sodium palmitate (skin antiseptic) |
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Control of Microbial Growth by
oxidation of -SH Groups reaction catalyzed by (2): reaction: |
Control of Microbial Growth by
oxidation of -SH Groups reaction catalyzed by (2): peroxidases and halogens reaction: R-SH + HS-R --> R-S-S-R' (active) (active) (inactive) |
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Modification of -SH Gropus
Reaction catalyzed by: eg: |
Modification of -SH Gropus
Reaction catalyzed by: heavy metal salts eg: bismuth salicylate active ingredient in Pepto-Bismol |
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Lethal Damage to DNA:
expose to: causes: |
Lethal Damage to DNA:
expose to: electroagnetic radiation causes: causes irreversible damage to DNA (ss and ds breaks, UV also causes thymine dimers) |
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Lethal Damage to DNA
Electromagnetic Radiation 3 types and uses: |
Lethal Damage to DNA
Electromagnetic Radiation 3 types: 1) Ultraviolet irradiation (germicidal lams to clean rooms (air and surfaces)) 2) X rays (sterilize food products) 3) Cobalt 60 (gamma rays) (sterilize disposable plastic products) |
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Miscellaneous Sterilization Methods (3)
All are: |
Miscellaneous Sterilization Methods (3)
All are: Alkylating agents 1) Formaldehyde gas 2) Glutaldehyde 3) Ethylene oxide - mutagenic |