Microbiology Chapter 7 Quiz

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Questions and Answers

What should be done when inoculating to avoid cross-contamination?

Open plates to ensure they are not contaminated.

Perform inoculations away from plate 1. (correct)

Label all plates before inoculation.

Inoculate plates 1 and 2 simultaneously.

At what temperature should plates 3, 4, 5, 6, and 7 be incubated?

20°C

25°C

30°C

37°C (correct)

What information is required when labeling the base of each plate?

The cost of materials used.

The date and type of exposure. (correct)

The laboratory procedure followed.

The estimated growth time.

How long should plates be incubated for?

24 to 48 hours. Signup and view all the answers

When preparing to observe colonies, what drawing details should be included?

Drawings should include side views of colonies. Signup and view all the answers

What is the function of Kohler illumination in microscopy?

To uniform the light source on the specimen Signup and view all the answers

What adjustment should be made if the field appears unevenly illuminated?

Adjust the condenser height to focus the edges of the diaphragm Signup and view all the answers

What happens when the field diaphragm is closed?

The amount of light entering the objective lens decreases Signup and view all the answers

How can the light in the field of view be centered?

By using the condenser centering screws Signup and view all the answers

Why is it necessary to adjust the condenser in microscopy?

To ensure uniform illumination across the field Signup and view all the answers

How many ocular units correspond to a distance of 1,500 µm?

47 ocular units Signup and view all the answers

What is the calibration value for one ocular unit (OU) based on the provided information?

32 µm/OU Signup and view all the answers

Which objective lens has a total magnification of 400X?

High-Dry Power Signup and view all the answers

What should be done if the calculated ocular unit values differ when measuring?

Take the arithmetic mean of the values Signup and view all the answers

Using the information given, what is the distance measurement associated with 25 ocular units?

800 µm Signup and view all the answers

If using the scanning objective at 40X magnification, what is the calibration in µm per ocular unit?

32 µm/OU Signup and view all the answers

Which total magnification corresponds to the low power objective?

100X Signup and view all the answers

What is the correct relationship between ocular units and the stage micrometer distance?

Ocular units can be calculated by dividing distance by units Signup and view all the answers

How many ocular units does 800 µm span?

25 ocular units Signup and view all the answers

Which of the following is true about measuring specimens with an ocular micrometer?

It must be calibrated for each objective Signup and view all the answers

Study Notes

Inoculation Procedure

Inoculate away from plate 1 to prevent cross-contamination.
Plates 7 and 8 should remain covered and not be opened.
Label the base of each plate with the date, exposure type, and group name or number.
Invert all plates during incubation for consistency.

Incubation Conditions

Incubate plates 1, 2, and 8 at 25°C.
Incubate plates 3, 4, 5, 6, and 7 at 37°C.
Incubation time ranges from 24 to 48 hours for optimal microbial growth.

Observations and Drawings

Use provided circles as Petri dishes for drawing colony observations.
Choose two different colonies from each plate for detailed illustrations.
Label drawings with incubation time, temperature, and inoculum source, including colony color and abundance.

Microscope Techniques

Kohler illumination improves uniform lighting when focusing on specimens.
The field diaphragm can be adjusted to enhance light quality for clearer visibility.
Adjust condenser height and centering for optimal field diaphragm visibility.

Ocular Micrometer Calibration

Total magnifications vary across objectives: Scanning (40X), Low Power (100X), High-Dry Power (400X), Oil Immersion (1000X).
Use ocular micrometer to measure specimens by calculating ocular unit values based on stage micrometer measurements.

Bacterial Emulsion Preparation

Prepare smears of different organisms on slides without mixing to avoid cross-contamination.
Heat-fix slides by passing through a flame but avoid overheating to minimize aerosol production.
Follow staining protocols for consistent results, with specific times for crystal violet and safranin.

Safety and Disposal Practices

Dispose of used pipette and emulsion slides in designated disinfectant jars or sharps containers to ensure biohazard safety.
Use sterile tools, such as inoculating needles, especially for BSL-2 organisms, and properly disinfect after use.

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Description

Test your knowledge with this quiz based on Chapter 7 of Bailey & Scott's Diagnostic Microbiology. Focus on important practices for inoculation and contamination prevention techniques. Perfect for students learning about microbiological methods and laboratory safety.