ATI RN
microbiology chapter 1 test bank Questions
Question 1 of 5
Low-power microscopes designed for observing fairly large objects such as insects or worms are
Correct Answer: D
Rationale: The correct answer is D: stereomicroscopes. These types of microscopes, also known as dissecting microscopes, are designed for observing larger objects like insects or worms. They have a lower magnification power compared to electron microscopes (A), which are used to observe smaller objects at a much higher resolution. Dark-field microscopes (B) are used for observing live and unstained samples with high contrast, not specifically for larger objects. Fluorescence microscopes (C) are used to observe specimens that fluoresce under specific wavelengths of light, not necessarily for large objects like insects or worms. Therefore, the most suitable choice for observing fairly large objects like insects or worms is stereomicroscopes.
Question 2 of 5
A patient with pneumonia had a sputum smear stained by the Gram method revealing Gram-positive cocci in pairs. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. The presence of Gram-positive cocci in pairs indicates a bacterial morphology consistent with Streptococcus pneumoniae, a common cause of pneumonia. This bacterium is known to appear in pairs or short chains on Gram stain. Staphylococcus aureus (B) typically presents as clusters of Gram-positive cocci, Neisseria meningitidis (C) is a Gram-negative diplococcus, and Klebsiella pneumoniae (D) is a Gram-negative rod, making them less likely causative agents in this scenario.
Question 3 of 5
A patient with a respiratory infection had sputum cultured on Endo agar, revealing green colonies. The bacteria were Gram-negative rods. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. Pseudomonas aeruginosa is known to produce green colonies on Endo agar due to its pyoverdin pigment. It is also a Gram-negative rod. P. aeruginosa commonly causes respiratory infections in immunocompromised patients. Escherichia coli (B) typically produces pink colonies on Endo agar and is more associated with gastrointestinal infections. Salmonella typhi (C) and Shigella dysenteriae (D) are both Enterobacteriaceae that usually do not produce green colonies on Endo agar and are more associated with gastrointestinal infections as well.
Question 4 of 5
A 3 m.o. baby has white film on the mucous membrane of his mouth, tongue and lips. A doctor suspected candidosis. What nutrient medium should be applied for inoculation of the material under examination in order to confirm this diagnosis?
Correct Answer: A
Rationale: Step-by-step rationale for why Answer A (Sabouraud's) is correct: 1. Sabouraud's agar is a selective medium for fungi. 2. Candida is a type of fungus causing candidosis. 3. Sabouraud's agar promotes fungal growth. 4. Candida will grow on Sabouraud's agar, confirming the diagnosis. 5. Other choices are for bacterial culture, not suitable for fungal growth. Summary: - Endo, Jensen's, and Roux are not appropriate for fungal culture. - Sabouraud's agar specifically supports fungal growth, making it the correct choice for confirming candidosis.
Question 5 of 5
Which one is true about the laboratory diagnosis of urinary tract infections
Correct Answer: D
Rationale: The correct answer is D because it encompasses the true statements regarding the laboratory diagnosis of urinary tract infections. A: Bacteriuria of less than 10^5 can be significant in treated patients due to the development of antibiotic resistance. B: Staphylococcus aureus, Salmonella typhi, and Mycobacterium tuberculosis may be significant regardless of quantity due to their pathogenic nature. C: Leukocyturia indicates inflammation, and even a lower number of leukocytes can be clinically significant. Therefore, option D covers all these aspects making it the correct choice.