Short Fridays Test 1 Flashcards
(60 cards)
Purpose of carbohydrate fermentation test
- To determine an organisms ability to ferment a specific carbohydrate with the production of acid with or without the production of gas
Purpose of urease test
- Demonstrating hydrolysis of urea.
(Largely produced by Proteus, Morganella, and some providencia species)
(In small amounts in other genera like (E.g. Klebsiella, Enterobacter, Serratia, Citrobacter and Yersinia)) - Usefull for screening colonies of yeasts for possible cryptococci
Purpose of Indole test
- To detect the production of Indole from tryptophan
- Especially useful in differentiating Escherichia coli from the Klebsielleae and Proteus mirabilis from other Proteeae
Purpose of Voges-Proskauer test
- Detecting production of acetoin (an intermediate in the formation of butylene glycol), by organisms that ferment glucose by way of the butylene glycol fermentation pathway.
- Differentiates Klebsielleae from the Escherichieae
Purpose of methyl red test
- Demonstrating an acidic pH change resulting from mixed acid fermentation of glucose in an indicator medium.
- Differentiate the Escherichieae from the Klebsielleae
Purpose of catalase test
- Separate Straphylococci (catalase positive) from streptococci (catalase negative)
Purpose of coagulase test
- Separate Staphylococcus aureus and other coagulase (like staphylococci) which possess coagulate activity from Staphylococcus epidermidis and other coagulate negative Siophs which do not.
Purpose of the DNase test
- To separate Staphylococcus aureus from Staphylococcus epidermidis.
- Most S. Aureus have deoxyribonuclease activity, while only a very small percentage of S. Epidermidis elaborate this enzyme. DNase activity is also useful for identifying certain gram-negative bacilli (E.g. Serratia and Aeromanas
Purpose of the H2S test
- Detecting of fecal origin. (Some are able to reduce organic sulfur to sulfide as H2S gas)
- To detect the ability of bacteria to produce H2S gas
- Differentiation of Salmonella spp and Erysipelothrix spp (H2S positive) from Shigella spp and Lactobacilli (H2S negative)
For what can affect the ability of an organism to ferment (chemically change) a carbohydrate for the fermentation test
A specific enzyme to degrade (break down) the substrate
What is the importance of an organism fermenting a carbohydrate for the fermentation test
The different fermentation patterns used for members of enterobacteriaceae are a way for them to be identified
What are the steps of the fermentation test
- A filtered solution of a specific carbohydrate is measured
2.This solution is added to a sterile basal medium - A final carbohydrate concentration is then measured
What is this final carbohydrate concentration for the fermentation experiment
0.5-1%
Why is it important to use a filtered solution for the fermentation experiment
Prevent any possible degradation of those carbohydrates susceptible to autoclaving
How is acid production measured after fermentation test
By the colour change of an indicator placed in the medium
What is gas production detected by after the fermentation test
An entrapment of air bubbles
Where is the entrapment of air bubbles seen after the fermentation test
An inverted durham tube
For the urea experiment what enzyme hydrolyses urea
urease
What are the products of the reaction involving urea and urease
ammonia and carbon dioxide
What is formed and what does it do after the urea experiment
Ammonia is formed. It alkalises the medium
What is also seen happening and what does it mean in the urease experiment
A colour change of Light orange to magenta. It means a Ph shift from 6.8-8.1
Which indicator is used for the urease experiment
phenol red
What enzyme deaminates tryptophan in the indole test
tryptophanase
What is tryptophan converted to in the indole test
indole, ammonia and pyruvic acid
