Disk Diffusion test
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Transcript of Disk Diffusion test
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Disk Diffusion test
Antibiotic resistant mutant colonies within zone of inhibition
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Chemical substances used to prevent microbial growth on the surface of living tissue
Antiseptics
Disinfectants
Chemical substances used to prevent microbial growth on inanimate surfaces
Decontamination: Decreasing microbial burden on a material in order to make it safe to handle (i.e. use of disinfectants).
Sterilization: Complete destruction of all microorganisms on a material. Examples include: AutoclavingIncinerationEthylene oxideIrradiation
Spore indicators validate sterilization
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Microbes Ranked by Susceptibility to Disinfectants
Least Susceptible
Most susceptible
Lipid Enveloped Viruses (flu)
Most Bacteria
Fungi
Non-Enveloped Viruses
Mycobacteria (tuberculosis)
Spore forming bacteria (Bacillus, Clostridia)
StrengthExample Disinfectant
Formaldehyde
Bleach
Alcohol andMost household disinfectants
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StaphylococcusGram + cocciIn clumps
StreptococcusGram + cocci in chains
Gram + rodsBacillus
Gram neg. cocci
Gram neg. rods
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Results• Acid-fast cells stain
reddish-purple• nonacid-fast cells
stain blue
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Results:
• Endospore will stain green
• Vegetative cell will stain pink
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SELECTIVE, DIFFERENTIAL AND ENRICHED MEDIA
Review the complete presentation.
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1 2 3 4 1) Aerobe2) Obligate anaerobe3) Micro-aerophile4) Facultative anaerobe
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GAS PAK SYSTEM
• Uses an anaerobic jar which contains:1) inoculated plates to be grown anaerobically
are placed inside2) gas generator envelope—produces H+ and
CO2 upon the addition of water3) paladium catalyst—combines H+
with oxygen to form H2O4) indicator strip—impregnated with either
methylene blue or resazurin to indicate whether anaerobic conditions inside the jar have been achieved
(The methylene blue indicator strip becomes colorless in absence of oxygen.)(Resazurin becomes pink in presence of oxygen.)
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GasPak Anaerobic System
The GasPak Anaerobic System is used to create an oxygen-free environment for the growth of anaerobic microorganisms. Inoculated plates or tubes are placed inside the chamber, and anaerobic conditions are created by adding water to a gas generator envelope that is placed in the jar just before sealing. The envelope contains two chemical tablets, sodium borohydride and sodium bicarbonate. Water reacts with these chemicals, producing hydrogen gas and carbon dioxide. The hydrogen gas combines with free oxygen in the chamber to produce water, removing all free oxygen from the chamber. This reaction is catalyzed by the element palladium, which is attached to the underside of the lid of the jar. The carbon dioxide replaces the removed oxygen, creating a completely anaerobic environment.
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Use Mueller-Hinton plates: (MH) enriched media supplemented with beef broth and other nutritional supplements facilitates growing fastidious organisms
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Disk Diffusion test
Antibiotic resistant mutant colonies within zone of inhibition
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