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CLINICAL BACTERIOLOGY
LABORATORY
INHIBITION & DESTRUCTION OF MICROORGANISM BY PHYSICAL AGENTS
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Cards (15)
Sterilization
All forms of microbial life including
bacterial spores
are killed
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Disinfection
Pathogenic
organisms but not necessarily all microorganisms or
spores
are destroyed
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Moist heat under steam pressure
1.
Kills
by
coagulation
of proteins including enzymes and structural protein
2.
Autoclave
at 121°C at 15psi for 15-20 minutes to
sterilize
medical liquids and instruments
3.
Autoclave
at 132°C at 15psi for 30-60 minutes to
sterilize infectious
medical waste
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Quality control
(QC) for
sterilization
Done to ensure
sterilization
is effective
Uses
Bacillus stearothermophilus
in vials or spore-strip sets incorporated in
autoclave
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Dry heat
1. Causes protein
oxidation
2. Hot
air sterilization
using ovens at 160-180°C for 1.5-3 hours
3. Used for sterilization of
glassware
for lab use
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Nutrient broth
Culture medium used for this activity
Turbidity
indicates growth of microorganisms
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Procedure
1. Transfer impregnated filter paper into nutrient broth and
incubate
2.
Immerse
inoculated nutrient broth in boiling water bath for 30 minutes
3.
Immerse
inoculated nutrient broth in 80°C water bath for 30 minutes
4. Transfer
autoclaved
and
hot air
subjected impregnated filter papers into nutrient broth
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Observation is indicated as
turbid
or
clear
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Interpretation
Bacteria
were killed or
bacteria
were not killed
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Lactose broth with Durham's fermentation tube
Selective
culture medium
Andrade's indicator turns pink in presence of acid
Fermentation of
lactose
produces
acid
and gas
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Evidence of bacterial growth after incubation includes
turbidity
, presence of
gas
, and change in pH
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Disinfectants used
Lysol
1:1000
Mercuric Chloride
Tincture of
Iodine
70
% Alcohol
3
% H2O2
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Procedure for testing disinfectants
1. Transfer 1 mL of cultured E. coli to 10 mL of disinfectant
2. Transfer inoculum from mixture to Lactose broth tube at 5, 10, 15, and 30 minutes
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Reading of the result notes the presence of
gas
inside the
Durham's fermentation tube
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Interpretation of the result
Bacteria
were killed or
bacteria
were not killed at the specific time
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