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30 Cards in this Set

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microbial death defn:
irreversible loss of the ability to divide - probability of any one cell dying is constant per unit of time
bacteriocidal defn:
describes a compound/drug that kills bacteria
bacteriostatic defn:
describes a compound/drug that inhibits growth of bacteria
sterilization defn
the complete killing or removal of all living microbes from a growth medium
disenfectant defn
a chemical agent which causes death of microbes and reduces numbers, but does not produce a sterile environment
biocide/germicide defn:
refers to chemical agents that kill microbes
sanitizers defn:
only reduce the numbers of microbes on inanimate surfaces
detergents defn:
disperse and remove soil and organic material from surfaces and permit disenfectants to act
thermal death point defn:
the lowest temperature at which a 10 min exposure of a given volume of a broth culture results in sterilization
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
Disenfection goal:
to reduce numbers, not produce a sterile environment
Chemotherapy goal:
kill all microbes
Selective toxicity related to:
5 chemotherapy mechanisms with high to low selective toxicity
Death Kinetics General Principles (3)
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)
Death Kinetics:
Environmental conditions determine:
Death Kinetics:
Environmental conditions determine: effectiveness of disenfectants
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
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
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)
Mechanisms of Chemical Disenfectants (5 mechanisms, 3 substances)
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)
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
Calculate PC
Cpd a kills bacteria in 10 min dillution 1:450
phenol kills bacteria in 10 min dillution 1:90
PC = 450/90 = 5
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
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
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
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)
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)
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
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)
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)
Miscellaneous Sterilization Methods (3)
All are:
Miscellaneous Sterilization Methods (3)
All are: Alkylating agents
1) Formaldehyde gas
2) Glutaldehyde
3) Ethylene oxide - mutagenic