1. Aseptic Technique – Inoculating Different Types of Media – DAY 2
SLOs:
Define fermentation and understand why a pH change is indicative of it
List and explain the necessary ingredients of a fermentation tube.
Perform and interpret carbohydrate fermentation tests.
Explain the mechanism of urea hydrolysis and the basis of a positive test.
Perform and interpret the urea hydrolysis test.
Explain the use of tetrazolium salt for agar deeps.

2. Possible Results for Carbohydrate Fermentation Tests
Interpretation
Symbol
Yellow broth, bubble in Durham tube
Fermentation with acid and gas as end products
A/G
Yellow broth, no bubble in Durham tube
Fermentation with acid end products; no gas produced
A/
Red or pink broth, no bubble in Durham tube
No fermentation; more or less degradation of peptones with varying quantities of alkaline end products
/
K if pH

3. Possible Reactions

4. Glucose Fermentation with Durham Tube

5. Lactose Fermentation

6. Sucrose Fermentation

7. urea This test checks if bacterium has enzyme urease
Medium contains urea, phenol red, peptones, glucose, potassium phosphate
Mainly used to differentiate Proteus from other Enterobacteriaceae

8. Table 18-1: Possible Results for Urease Test
Interpretation
Symbol
Up to 24 hours
24 hours to 6 days
All pink
Rapid urea hydrolysis; strong urease production +
Partially pink
All pink or partially pink
Slow urea hydrolysis; weak urease production
w +
Orange or yellow
No urea hydrolysis; urease is absent

10. Agar Deeps: What is happening?
From left to right: Micrococcus luteus, Pseudomonas aeruginosa, E. coli
the end