20 Questions
What is the purpose of heat fixing in smear preparation?
To kill the organism
What is the characteristic of a negative stain?
It is repelled by the negative cell wall
What is the purpose of a simple stain?
To show the morphology of bacteria
What is essential for successful identification of microbe?
Correctly handling the specimens
What is the main difference between a simple stain and a differential stain?
The number of reagents used
What is the function of Auxochrome in staining?
To allow the dye to form salt compounds that adhere to cells
What is the purpose of Gram stain?
To distinguish between bacterial groups
What is the purpose of macroscopic colonial morphology in phenotyping?
To examine the growth pattern of the bacteria
What is the concentration of agar in solid media?
1 - 2%
What is the purpose of culture media?
To provide an environment suitable for growth
What type of stain is used to identify special structures such as capsule?
Special Stains
What is a physical requirement for growth?
Temperature
What type of medium is used to identify microorganisms based on their ability to utilize a specific substrate?
Differential medium
What is the result of combining Benzene and Chromophore?
Chromogen
Why is labeling the slide important in slide preparation?
To keep track of the samples
Which of the following transport media is used for stool samples?
Carry Blair Transport Medium
What is an inorganic nutrient required for growth?
Phosphate
What is the purpose of the citrate utilization test?
To show ability to utilize a specific substrate
Which of the following is NOT a type of bacterial classification?
Classification based on habitat
What is the purpose of the H2S production test?
To test for metabolism of proteins and amino acids
Study Notes
Bacterial Identification
- Successful identification of microbe depends on: using aseptic techniques, correctly handling specimens, quickly transporting the specimen to the lab, and culturing and isolating quickly.
- Three types of identification methods: phenotyping, serological, and molecular.
Phenotyping
- Microscopic observation
- Macroscopic colonial morphology
- Culture media for growth
- Biochemical tests
Stains
- All dyes are salts that ionize
- Cationic and anionic dyes
- Staining techniques: single dyes, multiple dyes
- Chemical makeup of stains: benzene, chromophore, auxochrome
- Chromogen: a colored compound formed by combining benzene and chromophore
Staining Methods
- Negative Stain: acid dye, (-) chromogen, repelled by (-) cell wall, cells appear colorless against a dark background
- Simple Stain: one reagent used, soak smear 30-60 seconds, rinse with H2O, background stained, bacteria stained, basic dye, (+) chromogen
- Differential Stains: two or more reagents, distinguish between bacterial groups or specific structures
Gram Stain
- Time frame: 1 minute, 1 minute, 15 seconds, 1 minute
- Rinse with water between each step
- Example: Gram stain, Acid Fast Stain
Culture Techniques
- Used to support the initial growth and isolation of microorganisms
- Culture media: food material or substances required for growing microorganisms in vitro
- Provide an environment suitable for microorganism growth
Culture Media
- Classification based on agar concentration or consistency:
- Fluid (broth) media: 0% agar
- Semisolid media: 0.4-0.5% agar
- Solid media: 1-2% agar (1.5%)
- Diphasic media: agar portion and broth portion
- Classification based on nutritional component or ingredients:
- Simple or Basic medium
- Complex medium
- Synthetic or defined medium
- Special medium (enriched, enrichment, differential, selective, or indicator and transport medium)
Biochemical Tests
- Use: identification of microorganisms
- Classification:
- Test for metabolism of carbohydrates: sugars fermentation test and O/F test
- Test for specific break down of product: MR & VP
- Test to show ability to utilize a specific substrate: citrate utilization test
- Test for metabolism of proteins and amino acids: H2S production test, indole production test
- Test for enzymes: catalase, oxidase, urease
This quiz covers the identification methods of bacteria, including phenotyping, serological, and molecular methods, as part of the first year nursing faculty curriculum. It is based on Lecture No. 6 by Rasha Zeinalabdein, M.Sc. in Microbiology.
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