Microbio CHAPTER 1 If David's lesion is indeed being caused by a pathogenic organism, which of the following terms would be used to describe the relationship between David and the microbe?

Using the provided staining reactions and data table, what type of microorganism could be infecting David? Select all that apply. (NCLEX style)

Nocardia species Mycobacterium species

If this non-healing lesion is caused by a microorganism, what term best describes the relationship between it and David?

Parasitism

Which of the following types of microscopy could help to determine that David's infection was caused by a Mycobacterium? Select all that apply.

Staining swabbed samples with auramine-rhodamine, then using fluorescence microscopy Staining swabbed samples with fluorescently-labeled antibodies specific for mycobacterial cell wall proteins, then performing fluorescence microscopy

Why are lesions caused by Mycobacterium marinum usually only found on the extremities?

The extremities are a few degrees cooler than the rest of the body.

Choose the true statement(s) about the taxonomic hierarchy and its vocabulary terms. To be marked correct, you'll need to select all true statements, as there may be more than one correct answer.

The five-kingdom classification scheme includes: Animalia, Plantae, Fungi, Protista, and Monera. An example of a domain is Archaea.

Which of the following would make Koch's postulates impossible or difficult to fulfill in David's case? Select all that apply.

The infectious agent cannot be grown in the hospital lab. The infection is caused by two microorganisms working together. The infectious agent only infects humans. The wound is caused by cancer.

Only a handful of studies have been performed regarding treatment outcome of Mycobacterium marinum infections. You find a paper with the included data table that summarizes the findings of these studies. Based on the provided data table, what would be the best course of treatment for David? (NCLEX style)

Treat with a combination of streptomycin, isoniazid, and ethambutol for 5 weeks.

Which of the following is correctly written, based upon the rules of the binomial nomenclature system?

Escherichia coli In binomial nomenclature, we capitalize the genera name (the first name), lowercase the species name (the second name), and italicize the entire name. When handwriting the scientific name of an organism, you can underline the name rather than italicize. Do not italicize AND underline the name; this is why the choice "Escherichia coli" is incorrect.

A Gram stain is performed, but the decolorizer is left on too long. What results would be seen?

Gram-positive and Gram-negative organisms would be pink.

If David's lesion is indeed being caused by a pathogenic organism, which of the following terms would be used to describe the relationship between David and the microbe?

Parasitism

`Each of the following is a characteristic of bacteria in the genus Mycobacterium. Which characteristic would make them difficult to Gram stain?

Produces a waxy cell wall

Which of the following is (are) mismatched? To be marked correct, you'll need to select all mismatched statements, as there may be more than one correct answer.

Pure culture: diverse colonies evident Streak plate technique: broth culture To study microbes, growth media or mixtures of nutrients to support microbial growth are used. Growth media may come in a variety of consistencies, including solid media, which can be used to fill petri dishes for easier isolation and observation. It is often desirable to separate microbes from each other using different techniques such as the streak plate technique. The streak plate technique cannot be performed using a broth culture. Instead, a solidified agar in a plate is used to spread the sample so that individual colonies can be obtained for analysis. By performing this technique, a pure culture can be generated, which would have colonies that are fairly uniform in appearance. (Reference: We culture microbes so we can study them.)

A student from one of the research labs is having trouble preparing a slide for examination and photographing. The bacterial slide that he has brought to you was prepared using a commercially purchased stain. He has asked for your help in determining what he is doing wrong so that he can change the lab protocols and continue on with his project. After examining the slide under oil immersion, you determine that no bacteria are present even though the student is able to show you the culture he used to make that slide that has visible growth in the liquid medium. Which of the following statements does NOT explain the fact that there are no bacteria present on the student's slide?

Rinsing with alcohol during the washing step stripped the bacteria off the glass slide.

You volunteer to help the student with his fixation technique and in choosing a proper stain for the project he is working on. After watching and helping the student correct any problems with his fixation technique, you now need to determine which stains to use. The single criterion for the project is to be able to determine cell shape and size in a pure broth culture after some treatments. No differentiation between cell types is required (i.e., Gram-positive or Gram-negative), so you want to convince the student that a simple stain would be his best option. The charged dyes used in simple staining will penetrate the bacterial cell and will be retained after rinsing the slide with water to remove surplus dye. Which staining procedure would be best to use to stain the slides required for this student's project? Why?

The positively charged methylene blue will be attracted to the negatively charged components of the cell wall and will be retained.

Which of the following results could be obtained from Gram staining Staphylococcus aureus, a Gram-positive, acid-fast negative, coccus?

This organism is purple in the Gram stain (positive) and blue in the acid-fast stain (negative).

Why might David's repeated self-treatment with Neosporin-a suspension containing three different antibacterial medicines-not have cured his wound? Select all that apply. (NCLEX style)

Those particular antibiotics may not affect all bacteria. The infection could be caused by a virus. The concentration of the antibacterial agent may have been too low. This may not be an infection, but, instead, a cancer.

You have been asked to lead a demonstration for the undergraduate microbiology lab course about the uses of negative staining when studying bacteria. A "negative" stain does not stain the bacterial cell itself but stains the space between cells. Under magnification, the acidic (negatively charged) nature of the stain will be repelled by the negatively charged bacterial cell wall and will leave the cell colorless in a stained background. Negative stains are used primarily to reveal the presence of negatively charged bacterial capsules; therefore, they are also called capsule stains. Encapsulated cells appear to have a halo surrounding them. The negative stain procedure does not require heat fixation, which limits any chances of alteration in bacterial cell shape and size. The bacterial suspension is added to a drop of stain, such as nigrosin or eosin, and drawn across the glass slide using a coverslip. Nigrosin staining-not safranin staining-of Klebsiella pneumoniae will allow for the visualization of the cell shape and the determination of the presence of a capsule.

True

A new project has come up in the core center - a researcher wants to study bacterial biofilms and will need you to document the process of biofilm formation. Bacterial biofilms are colonies of different species of bacteria that interact and allow the bacteria to grow in a new environment. Since this will be a mixed culture, you will need to use a staining protocol that allows for differentiation between bacteria based on cell wall properties. The Gram staining procedure uses a series of stains and alcohol decolorization to differentially color different species of bacteria that may be present in the growing biofilm. This differential colorization will allow for determination of bacterial morphology and give some insight into the bacterial cell wall composition.

Unstained cells (start of process) All cells are stained purple. Dye molecules are rendered insoluble in presence of mordant; dye is rinsed away. Cell wall of Gram-negative cells is broken down; Gram-positive cells remain intact. Clear cells are stained a red or pink whereas the color of other cells remains unchanged. Stained cells (end of process)