OpenStax Microbiology Test Bank

Questions 82

ATI RN

ATI RN Test Bank

OpenStax Microbiology Test Bank Questions

Question 1 of 5

A 70-year-old man has developed prosphetic stomatitis. Apart of this he was found to have an evident lesion of mouth corners. Microscopical examination revealed large ovoid gram-positive cells. What microorganisms are most likely to be the leading etiological agent of such a lesion?

Correct Answer: A

Rationale: The correct answer is A: Candida fungi. In the context of a 70-year-old man with angular cheilitis (lesion at the corners of the mouth) and stomatitis, the presence of large ovoid gram-positive cells points towards Candida species, which are yeast fungi. Candida is a common opportunistic pathogen that can cause oral thrush and angular cheilitis in immunocompromised individuals, such as elderly people. Candida fungi are known to appear as large ovoid cells under microscopic examination. Summary of other choices: B: Streptococci are gram-positive bacteria and are not typically associated with large ovoid cells seen in this case. C: Staphylococci are also gram-positive bacteria and are not known to present as large ovoid cells in this context. D: Neisseria are gram-negative bacteria and are not the usual etiological agents for oral lesions like angular cheilitis.

Question 2 of 5

Koch apparatus uses temperature of:

Correct Answer: C

Rationale: The correct answer is C (100�C) because the Koch apparatus is used for sterilization, and the standard temperature for sterilization is 100�C. At this temperature, most microorganisms are killed, making it an effective method for sterilization. Choice A (90�C), B (95�C), and D (110�C) are incorrect because they are not commonly used temperatures for sterilization purposes. Choosing a temperature lower than 100�C may not effectively kill all microorganisms, while choosing a temperature higher than 100�C may lead to unnecessary energy consumption without providing additional sterilization benefits.

Question 3 of 5

Which of the following organisms belongs in the group I category?

Correct Answer: C

Rationale: The correct answer is C: Helicobacter pylori. Group I organisms are classified based on their low infectious doses and potential for bioterrorism. H. pylori is known to cause gastric ulcers and is categorized as a Group I organism due to its ability to cause disease at low doses. A: Francisella tularensis is a Group A bioterrorism agent, not Group I. B: Clostridium difficile is not typically classified as a Group I organism. D: Bacillus anthracis is a Group A bioterrorism agent, not Group I.

Question 4 of 5

What is the structure of the bacterial cell wall?

Correct Answer: A

Rationale: The correct answer is A: Peptidoglycan. Bacterial cell walls are composed of peptidoglycan, a unique macromolecule consisting of sugars and amino acids. This structure provides rigidity and protection to the cell. Lipopolysaccharides are found in the outer membrane of Gram-negative bacteria, not in the cell wall. Phospholipids are the main components of cell membranes, not cell walls. Chitin is a structural polysaccharide found in the cell walls of fungi and some algae, not bacteria.

Question 5 of 5

Which of the following bacteria IS NOT associated with skin infections?

Correct Answer: D

Rationale: Correct Answer: D (Clostridium difficile) Rationale: 1. Clostridium difficile is primarily associated with gastrointestinal infections, particularly antibiotic-associated colitis. 2. Staphylococcus aureus, Clostridium perfringens, and Pseudomonas aeruginosa are commonly associated with skin infections. 3. Staphylococcus aureus can cause impetigo, boils, and cellulitis. 4. Clostridium perfringens can cause gas gangrene. 5. Pseudomonas aeruginosa can cause hot tub folliculitis and swimmer's ear.

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