Lab Report 1-3 Questions

What is the difference between magnification and resolution?

Magnification refers to the enlargement in size of the image where resolution refers to the level of clarity of the image.

How would you describe the morphology and arrangement of the cells in your stained preparations?

P. aeruginosa were pink (gram-negative), bacilli colonies, were S. aureus were purple (gram-positive), cocci colonies. The mixture slide contained colonies of both samples.

Why is it important to steam the slides in the Ziehl-Neelson method?

Steaming water facilitated the staining of the cell by increasing the fluidity of the cell wall and permits the penetration of the stain.

You are viewing a clinical specimen that has been prepared using acid-fast stain. All of the organisms are stained blue, with both cocci and bacilli are present. What can you conclude? Assuming the bacilli are mycobacterial cells, what procedural error occurred?

This could be caused by decolorizing too much which results in the primary stain to be eliminated from the acid-fast positive cells, making them appear blue.

You are looking at the smear of the mixture. All of the cells, cocci and bacilli, appear deep purple. What could have gone wrong?

This could be caused by improperly performing the decolorizing step, resulting in the crystal violet to remain in the gram-negative cells.

The patient in the case file had to undergo a 4-moth course of treatment. A typical course of treatment or a bacterial infection is 10 day. What does this suggest about mycobacterial diseases. Noncompliance is a major issue when treating TB because the length of time of the treatment and the population typically exposed to the disease. What potential issue or problems does noncompliance pose in the area of public health?

This suggests that TB is difficult to treat due to the organism's protective or invasive nature. Noncompliance poses a risk of contagion or even potentially creating a drug-resistance strain of TB.

You mistakenly confuse the primary stain and counterstain. You initially stain the smear with safranin, add iodine, and then decolorize the counterstain with crystal violet. How does your mixed culture now appear when viewed with oil immersion?

This would cause all of the cells to appear purple, making it impossible to distinguish with cells are actually gram-positive, and which are gram-negative.

You are examining a prepared slide with 40x objective in place over the microscope. You rotate the 100x objective over the slide. When you look into the eyepiece, your specimen is gone! What happened?

Without the immersion oil, the light was able to refract away from the lens which resulted in a disappearance of the specimen.

What is the purpose of using immersion oil with the 100x objective?

Without the immersion oil, the light would refract and would not provide a detailed image of the sample due to the lack of visibility.

What would you observe if you decolorized your slide too much? How would your cells appear?

All of the cells would appear pink because too much acetone-alcohol will wash the crystal violet out of the cells making it impossible to distinguish between gram-positive and gram-negative bacteria.

Why is acid-fast stain clinically important?

Acid-fast staining allows us to identify organisms like mycobacterium that can cause diseases such as leprosy and tuberculosis.

Why is aseptic technique important?

Aseptic technique prevents any contamination of from pathogens to both your sample and yourself.

Bacillus, Staphylococcus, and Spirillum are all examples of bacteria. Saccharomyces is a yeast, a single-celled fungus. How does Saccharomyces microscopically differ from the other specimens?

The bacteria were all small, pink clusters of cells with various shapes and sizes. The Saccharomyces was similar in appearance but were blue and slightly larger than the bacteria.

As the staff biologist for the public health department, you examine the pond water (case file) under the microscope and notice high levels of green algae. What do you tell the members of the community about the safety of the water? What information do you need?

The high levels of green algae suggest the possible presence of bacteria that could be harmful to the ecosystem. Further tests and information should be gathered to determine the type of bacteria that are present to see if they pose a threat the ecosystem and/or the members of the community.

Which of the stained organisms was acid-fast?

The mycobacterium M. smegmatus was the acid-fast organism in this experiment.

The patient initially complained of pain in his hip and knee. A typical diagnosis from someone in this age range and with these symptoms would be osteoarthritis. Why did the physician assume a different cause?

The physician thought differently because the patient also had symptoms of fatigue, coughing, and losing weight.

Explain the relationship between the observe Gram reaction and bacterial cell wall structure.

There is more peptidoglycan in the gram-positive cells than the gram-negative, which causes the crystal violet to be trapped inside the cell during the decolorizing process.

You transfer a pure culture of S. aureus to a nutrient agar plate and incubate it for 24 hours. You observe white and yellow colonies; what do you conclude?

We can conclude that the sample was contaminated due to improper use of aseptic techniques, resulting in the growth of colonies of multiple types of bacteria.