ATI RN
microbiology an evolving science test bank Questions
Question 1 of 9
Detection of galactomannan and free mannan is used for diagnosing:
Correct Answer: A
Rationale: The correct answer is A: Aspergillosis and candidiasis. Galactomannan is a polysaccharide found in Aspergillus cell walls and is detected in patients with invasive aspergillosis. Free mannan is a polysaccharide found in Candida cell walls and is detected in patients with candidiasis. Therefore, detection of galactomannan and free mannan is specific for diagnosing Aspergillosis and candidiasis. Choices B, C, and D are incorrect as HIV infection, syphilis, and leptospirosis do not involve the detection of galactomannan or free mannan for diagnosis.
Question 2 of 9
Saprophytes are microorganisms which:
Correct Answer: B
Rationale: The correct answer is B: Cannot induce infectious disease. Saprophytes are microorganisms that obtain nutrients from decaying organic matter and do not cause infectious diseases in humans. They play a vital role in the ecosystem by decomposing dead organisms. Choice A is incorrect because saprophytes do not cause typical infections. Choice C is incorrect because saprophytes do not cause chronic infections. Choice D is incorrect because saprophytes do not cause mixed infections involving multiple pathogens. Therefore, the correct answer is B as saprophytes do not induce infectious diseases.
Question 3 of 9
A patient had been provisionally diagnosed with syphilis. A laboratory assistant took the blood serum for an immunologic test based on the detection of antibodies preventing the movement of treponemas and causing their death. What reaction was used for the diagnosis?
Correct Answer: A
Rationale: The correct answer is A: Immobilization. This technique is called the Treponema pallidum immobilization (TPI) test, used to diagnose syphilis. The rationale is as follows: 1. TPI test detects antibodies that prevent the movement of treponemas, causing their death. 2. By immobilizing the treponemas, it indicates the presence of specific antibodies against syphilis. 3. This test is highly specific for syphilis diagnosis as it directly targets the causative agent. Other choices are incorrect: B: Complement binding - Not specific to syphilis, more commonly used for other diseases. C: Agglutination - Detects clumping of particles, not specific to treponemas or syphilis. D: Precipitation - Involves the formation of a solid, not directly related to treponema movement or death.
Question 4 of 9
The process of bacterial conjugation involves:
Correct Answer: C
Rationale: The correct answer is C: Direct transfer of DNA between two bacterial cells. In bacterial conjugation, genetic material is transferred directly from one bacterial cell to another through a conjugative pilus. This process involves physical contact between the cells, followed by the transfer of plasmid DNA or chromosomal DNA. This mechanism allows for the exchange of genetic information between bacteria, leading to genetic diversity. Explanation of why other choices are incorrect: A: DNA transfer via bacteriophage - Bacteriophage is a virus that infects bacteria and transfers its genetic material, but this is not the mechanism involved in bacterial conjugation. B: Uptake of naked DNA from the environment - This process is known as transformation, where bacteria take up free DNA from the environment, but it is not specific to bacterial conjugation. D: Binary fission - Binary fission is a form of asexual reproduction in bacteria where a single cell divides into two identical cells, and it is not related to the process
Question 5 of 9
A 40-year-old man developed skin redness and an swelling in the neck area, where eventually a small abscess appeared. The section the focus is dense and yellow-green colored. In the purulent masses there are white granules. Histologically there are fungal druses, plasma and xanthome cells, and macrophages detected. Specify the most correct etiological name of this pathological process?
Correct Answer: A
Rationale: The correct answer is A: Actinomycosis. This is a chronic bacterial infection caused by Actinomyces species. In this case, the description of dense yellow-green colored focus, white granules in purulent masses, and presence of fungal druses, plasma cells, xanthome cells, and macrophages all match the characteristics of actinomycosis. Actinomycosis typically presents with abscess formation containing sulfur granules, which are yellowish and granular. The other choices (B: Furuncle, C: Carbuncle, D: Syphilis) do not fit the clinical and histological features described in the question, making them incorrect options.
Question 6 of 9
A patient with acute food poisoning had fecal cultures grown on Endo agar, resulting in colorless colonies. What microorganism is most likely responsible?
Correct Answer: A
Rationale: Step 1: Endo agar is a selective and differential media commonly used to isolate gram-negative bacteria. Step 2: Colorless colonies on Endo agar indicate the absence of lactose fermentation. Step 3: Salmonella is a gram-negative bacterium that does not ferment lactose, leading to colorless colonies on Endo agar. Step 4: Therefore, the correct answer is A: Salmonella. Summary: B: Escherichia coli ferments lactose, producing pink colonies on Endo agar. C: Staphylococcus is a gram-positive bacterium and would not grow on Endo agar. D: Shigella is a gram-negative bacterium but ferments lactose, resulting in pink colonies on Endo agar.
Question 7 of 9
Microscopy of stained (Ziehl-Neelsen staining) smears taken from the sputum of a patient with chronic pulmonary disease revealed red bacilli. What property of tuberculous bacillus was shown up?
Correct Answer: A
Rationale: The correct answer is A: Acid resistance. Tuberculous bacilli are acid-fast bacilli, meaning they resist decolorization by acid-alcohol after staining with Ziehl-Neelsen stain. This property is due to the high lipid content in the cell wall of Mycobacterium tuberculosis. Alkali resistance (B) and alcohol resistance (C) are not specific properties of tuberculous bacilli. Capsule formation (D) is a characteristic of some bacteria but is not a defining feature of tuberculous bacilli.
Question 8 of 9
Which of the following statements for genus Klebsiella is correct?
Correct Answer: A
Rationale: The correct answer is A because Klebsiella species have a real capsule, which is a distinguishing feature used for their identification. This capsule helps them evade the host immune response. Additionally, Klebsiella species are non-motile, meaning they do not possess flagella for movement. Choices B and C are incorrect because Klebsiella species are facultative anaerobes and do not form spores under any conditions. Choice D is also incorrect as option A is the correct statement for genus Klebsiella.
Question 9 of 9
On microscopic examination of leftovers of the canned meat eaten by patient with severe food toxicoinfection the following was detected: gram-positive bacilli with subterminal staining defect and configuration alteration of bacilli generally resembling a tennis racket. What agent was detected?
Correct Answer: A
Rationale: The correct answer is A: C. botulinum. The description of gram-positive bacilli with subterminal staining defect and tennis racket appearance is characteristic of Clostridium botulinum. The subterminal staining defect indicates the presence of spores, a feature of Clostridium species. The tennis racket appearance refers to the characteristic shape of C. botulinum spores. Choice B, P. vulgaris, is a gram-negative bacterium and doesn't match the description. Choice C, E. coli, is a gram-negative bacillus and doesn't exhibit the subterminal staining defect described. Choice D, S. aureus, is a gram-positive cocci and does not resemble the tennis racket appearance described.