Clinical Microbiology HW#1

CHAPTER 1

1. The term used to describe a disease-causing microorganism is: Pathogen

2. In the name Staphylococcus aureus, aureus is the: Specific name

3. A prokaryotic cell may possess each of the following cellular components EXCEPT: A nucleus

**A prokaryotic cell may possess a: cell wall, cell membrane, flagella, ribosomes

4. A student has obtained a sample of pond water for study. Using the high-power lens, he observes several cells with nuclei. He can conclude that the cells are NOT bacteria. TRUE

5. Some viruses can contain both DNA and RNA. FALSE

6. The first step for directly linking a microbe to a specific disease according to Kochs postulates is to: obtain a sample of blood or other body fluid from a diseased animal

7. All pathogens known to infect humans have been identified at this point in time. FALSE

8. All of the following factors contribute to the threat of emerging infectious diseases (EIDs) EXCEPT: vaccinations that control epidemiologic spread.

*Vaccination does not promote emerging infections but rather helps to control infections.

**These factors contribute to the threat of emerging infectious diseases (EIDs):

spread of known diseases to new geographic regions or populations by modern transportation

increased human exposure to new, unusual infectious agents in areas that are undergoing ecological changes, such as deforestation and construction

evolutionary changes to existing organisms through genetic changes.

***HINT: Emerging infections represent a special danger. Consider what features or human actions may contribute to the new pathogens, re-emerging diseases, or increased incidences of these types of infections.

CHAPTER 2

1. What is the type of bond between the hydrogen of one molecule and the nitrogen of another
molecule? Hydrogen bond

2. Antacids neutralize acid by the following reaction. Identify the salt in the following equation:
Mg(OH)₂ + 2HCl → MgCl₂ + H₂O                 MgCl₂

3. Identify the following reaction: Glucose + Fructose → Sucrose + Water 

        dehydration synthesis reaction

4. An E. coli culture that has been growing at 37°C is moved to 25°C. Which of the following changes must be made in its plasma membrane? The number of unsaturated chains must increase.

5. Which of the following statements about water is true? Water plays an important role in dehydration synthesis.

CHAPTER 3

1. Place the steps of the Gram stain in the correct order: Alcohol-acetone; Crystal violet; Safranin; Iodine

                Crystal violet – iodine – alcohol acetone – safranin

2. Which of the following is NOT true regarding the acid-fast stain? If cells are acid-fast, they are gram-negative

**TRUE regarding the acid-fast stain:

Acid-fast cells appear red in a completed acid-fast stain

Acid-fast cells retain the primary dye after treatment with acid-alcohol

It is used to identify members of the genus Mycobacterium

Non-acid-fast microbes appear blue in a completed acid-fast stain

3. The negative stain is used to: visualize capsules

4. You are performing a Gram stain on gram-negative bacteria and you stop after the addition of the mordant. What is the appearance of the bacteria at this point? Purple

5. Which type of stain is most useful in helping clinicians to decide which antibiotic to prescribe for a bacterial infection? Gram stain

6. A student creates a Gram stain on a bacterial specimen that has a mix of gram-negative and gram-positive organisms but accidentally forgets the decolorizer step. What would the outcome of the Gram stain be? All organisms would appear purple (gram-positive).

*Without the decolorizer step, all the organisms retain the purple stain.

**HINT: Imagine what each step of the Gram stain looks like when it is done correctly. How would this incorrect process affect the final outcome?

7. Consider the following situations, and determine when a simple stain could be used instead of a Gram stain.

A microbiologist is trying to determine whether a specimen contains bacteria or fungi.  
*A simple stain is used to visualize the entire organism and highlight cellular shapes or structures. In this case, differentiation of bacterial characteristics is not necessary.

**HINT: Consider the purpose or final outcome of the two stains.