Microbiology Chapter 13 Test Bank

Microbiology Chapter 13 Test Bank Related

Review Microbiology Chapter 13 Test Bank related questions and content

During the skill-building session in microbiology the students need to stain the prepared and fixed sputum smears obtained from a tuberculosis patient. What staining technique should be used in this case?

  • A. Gram
  • B. Giemsa
  • C. Ziehl-Neelsen
  • D. Burry
Correct Answer: C

Rationale: The correct staining technique for staining sputum smears from a tuberculosis patient is Ziehl-Neelsen staining. This technique uses a carbol fuchsin stain that specifically stains acid-fast organisms like Mycobacterium tuberculosis. The steps involved include staining with carbol fuchsin, decolorizing with acid-alcohol, counterstaining with methylene blue, and then examining under a microscope. This staining method is crucial for detecting the acid-fast bacilli characteristic of tuberculosis.

Explanation for incorrect choices:
A: Gram staining is used to differentiate bacteria into Gram-positive and Gram-negative, not suitable for acid-fast organisms like Mycobacterium tuberculosis.
B: Giemsa staining is used for detecting parasites and certain types of white blood cells, not specific for acid-fast bacteria.
D: Burry staining is not a recognized staining technique in microbiology for staining acid-fast organisms.

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A male patient has been diagnosed with gastric ulcer. Bacteriological examination of biopsy material from the affected part of stomach revealed small colonies of gram-negative, oxide reductase-positive flexibacteria that grew on the chocolate agar on the fifth day. Which of the following microorganisms is the most likely causative agent?

  • A. Helicobacter pylori
  • B. Campilobacter jejuni
  • C. Campilobacter fetus
  • D. Mycoplasma hominis
Correct Answer: A

Rationale: The correct answer is A: Helicobacter pylori. This bacterium is the most likely causative agent of gastric ulcers. Here's the rationale:
1. Helicobacter pylori is commonly associated with gastric ulcers.
2. It is a gram-negative bacterium that grows on chocolate agar and is oxide reductase-positive.
3. The slow growth on the fifth day is characteristic of H. pylori.
4. Campylobacter jejuni and Campylobacter fetus are not typically associated with gastric ulcers.
5. Mycoplasma hominis is a bacterium that lacks a cell wall and is not commonly found in gastric ulcers.

Which of the following bacteria should be handled in a Biosafety Level 2 facility?

  • A. Micrococcus luteus
  • B. Bacillus subtilis
  • C. Salmonella
  • D. Staphylococcus epidermidis
Correct Answer: C

Rationale: The correct answer is C: Salmonella. This bacterium should be handled in a Biosafety Level 2 facility due to its potential to cause disease in humans. Salmonella is a pathogenic bacterium that can cause foodborne illnesses and infections. Handling it in a Biosafety Level 2 facility ensures proper containment and protection of personnel.

A: Micrococcus luteus and B: Bacillus subtilis are common environmental bacteria that do not pose significant risks to human health, so they can be safely handled in lower biosafety levels.

D: Staphylococcus epidermidis is a common skin commensal bacterium that is generally not considered highly pathogenic, so it does not require Biosafety Level 2 containment.

Vaginal infections that are resulting from an overgrowth of normal flora are called:

  • A. endogenous infections
  • B. chronic infections
  • C. iatrogenic infections
  • D. fatal infections
Correct Answer: A

Rationale: The correct answer is A: endogenous infections. This term refers to infections caused by microorganisms that are normally present in or on the body. In the context of vaginal infections, an overgrowth of the normal flora can lead to an imbalance and result in infection. Choice B, chronic infections, does not specifically address the source of the infection. Choice C, iatrogenic infections, refers to infections caused by medical intervention, not normal flora overgrowth. Choice D, fatal infections, is incorrect as it does not describe the nature or source of the infection. In summary, the term "endogenous infections" accurately describes the scenario of vaginal infections caused by an overgrowth of normal flora.

Laboratory diagnosis of rabies includes all of these except:

  • A. Looking for Negri bodies
  • B. Intracerebrally infected mice
  • C. Looking for Ernst-Babes granules
  • D. Immunofluorescence method
Correct Answer: C

Rationale: The correct answer is C: Looking for Ernst-Babes granules. Laboratory diagnosis of rabies typically involves looking for Negri bodies in the brain tissue, intracerebrally infecting mice for virus isolation, and using immunofluorescence method to detect viral antigens. Ernst-Babes granules are not associated with rabies virus and are not used in the diagnosis of rabies. Therefore, choice C is incorrect.

Fungi are free-living _________ organisms:

  • A. autotrophic
  • B. chemotrophic
  • C. heterotrophic
  • D. phototrophic
Correct Answer: C

Rationale: The correct answer is C: heterotrophic. Fungi are heterotrophic organisms that obtain nutrients by absorbing organic compounds from their environment. They do not produce their own food through photosynthesis (option A: autotrophic) or chemosynthesis (option B: chemotrophic). Fungi also do not rely on light for energy (option D: phototrophic). Therefore, the correct choice is C as it accurately describes the nutritional mode of fungi.

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