Identification Techniques for Enteric Pathogens
| Purpose | To study some biochemical reactions of Salmonella and Shigella |
| Materials | TSI slants SIM tubes MR-VP broths Simmons citrate slants Urea broth tubes Phenylalanine agar slants Lysine and ornithine decarboxylase broths Mineral oil in dropper bottle Sterile 1.0-ml pipettes Pipette bulb or other aspiration device Sterile empty tubes Xylene Kovac’s reagent Methyl red indicator 5% alphanaphthol 40% sodium or potassium hydroxide 10% ferric chloride Agar slant cultures of Salmonella and Shigella species |
Procedures
- You will be assigned a culture of either Salmonella or Shigella. Inoculate one tube of each medium provided (i.e.:TSI; SIM; MR-VP broth; citrate slant; urea, lysine, and ornithine broths; and phenylalanine agar).
- Incubate all tubes at 35°C for 24 hours.
- Complete the IMViC and PD tests (see Experiment 24.1). Read and record all biochemical reactions under Results. Observe your neighbors’ results and record all information for both organisms.
| Purpose | To illustrate identification of a microorganism by the slide agglutination technique |
| Materials | Glass slides 70% alcohol Saline (0.85%) Capillary pipettes Heat-killed suspension of E. coli or Salmonella E. coli or Salmonella antiserum |
Procedures
- Carefully wash a slide in 70% alcohol and let it air dry..
- Using a glass-marking pen or pencil, draw two circles at opposite ends of the slide..
- Using a capillary pipette, place a drop of saline in one circle. Mark this circle “C,” for control..
- With a fresh capillary pipette, place a drop of antiserum in the other circle..
- Use another pipette to add a drop of heat-killed bacterial suspension (this is the antigen) to the material in each circle..
- Pick up the slide by its edges, with your thumb and forefinger, and rock it gently back and forth for a few seconds..
- Hold the slide over a good light and observe closely for any change in the appearance of the suspension in the two circles.
Results
- In the following diagram indicate any visible difference you observed in the suspensions at each end of the slide. 192 Diagnostic Microbiology in Action
- State your interpretation of the result.
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