Lab Quiz Flashcards
What is the goal of differential media
It will aid in the identification of unknown gram negative rods in the Enterobacteriaceae family
Enzymatic activity of bacteria can be observed by using what?
Differential media
Enterobacteriaceae family include
Normal gastrointestinal microbiota, opportunists, and pathogens.
Infections cause by enterics include
Sepsis and meningitis
Types of standard differential tube media:
- Simmon’s Citrate Agar (SCA)
- Urea agar
- Sulfide-Indole-Mobility (SIM) medium
- Triple Sugar Iron ( TSI)
SIM media
Is a combined media that tests for motility, sulfur reduction to hydrogen sulfide H2S
H2S production in SIM:
What does the SIM media contains? What color is it turn when combined to H2S?
SIM contains ferrous sulfate ( iron salt)
That turn black when combine to H2S gas
Motility in SIM:
When are bacteria motile? Non motile?
If the bacteria swim away from the line of inoculation (stab), they are motile.
If the bacteria grow only along the stab line, they are non motile.
What is tryptophanase?
It is an enzyme produce by some bacteria.
What does tryptophanase do?
Are able to hydrolyze the amino acid tryptophan producing Indole and pyruvate.
Simmon’s Citrate is used to
Differential gram negative bacteria on the basis of citric acid utilization.
What does agar medium contains?
Sodium citrate as the only available carbon source.
What indicator the medium agar contain
Bromthymol blue, which is green at pH 6.9 and blue at pH 7.6
Organisms which have the enzyme citrase, are able of what?
They are able to to utilize the sodium citrate and nitrogen sources and produce ammonia.
Convert the agar to alkaline pH and a blue color
Triple Sugar Agar contains how many carbohydrates?
The medium contain what?
What indicator? Color?
- Three carbohydrates : glucose, sucrose and lactose.
- Peptones as a carbon and nitrogen source
- phenol red ( is yellow in acidic pH and pink red I. Alkaline pH).
