ATI RN
Microbiology An Introduction 12th Edition Test Bank Questions
Question 1 of 9
In the South and Central America there can be found a species of trypanosomes that is the causative agent of Chagas disease. What animal is the infection carrier specific to this disease?
Correct Answer: A
Rationale: The correct answer is A: Triatomine bug. Triatomine bugs, also known as "kissing bugs," are the specific carrier of the trypanosomes that cause Chagas disease. These bugs transmit the parasite through their feces, which contain the infectious forms of the trypanosomes. When the bug bites a human or animal, it defecates near the bite wound, allowing the parasites to enter the bloodstream through the broken skin. Mosquitoes (B) transmit diseases like malaria and dengue fever, not Chagas disease. Tsetse flies (C) are known for transmitting African trypanosomiasis (sleeping sickness), not Chagas disease. Cockroaches (D) are not known to transmit Chagas disease.
Question 2 of 9
A bacteriological laboratory has received smears from the sputum of a patient with a chronic pulmonary disease. Microscopical examination of the smears stained by the Ziehl-Neelsen technique revealed red bacilli. What property of the tuberculosis bacillus has shown itself?
Correct Answer: A
Rationale: The correct answer is A: Acid resistance. The Ziehl-Neelsen staining technique is specifically used to detect acid-fast bacteria like Mycobacterium tuberculosis, which is resistant to acid decolorization. This property allows the tuberculosis bacillus to retain the stain even after exposure to acid-alcohol, appearing red under the microscope. Explanation of incorrect choices: B: Alkali resistance - This property is not relevant in the context of Ziehl-Neelsen staining for acid-fast bacteria. C: Alcohol resistance - While alcohol resistance is related to acid-fastness, it is not the specific property highlighted by Ziehl-Neelsen staining. D: Capsule formation - Capsule formation is a different characteristic and not directly related to the staining behavior of acid-fast bacteria in the Ziehl-Neelsen technique.
Question 3 of 9
The optochin sensitivity test demonstrates:
Correct Answer: B
Rationale: The optochin sensitivity test is used to differentiate Pneumococcal (Streptococcus pneumoniae) from other streptococci. Optochin sensitivity is a characteristic feature of Pneumococcal, as it inhibits its growth. The test involves placing optochin discs on a culture plate and observing the zone of inhibition around the disc for Pneumococcal. Neisseria gonorrhoeae, Staphylococci, and Group A streptococci do not exhibit optochin sensitivity, making them incorrect choices. In summary, the optochin sensitivity test is specific to Pneumococcal, making choice B the correct answer.
Question 4 of 9
An example of selective media is:
Correct Answer: A
Rationale: The correct answer is A: McConkey agar. Selective media selectively inhibit the growth of certain organisms while allowing others to grow. McConkey agar contains crystal violet and bile salts that inhibit the growth of Gram-positive bacteria, making it selective for Gram-negative bacteria. Choices B and C are not selective media, as they do not specifically inhibit the growth of certain types of bacteria. Choice D is incorrect as McConkey agar is indeed an example of selective media.
Question 5 of 9
Which of the following bacteria is capable of producing an endotoxin that can lead to septic shock?
Correct Answer: D
Rationale: The correct answer is D: All of the above. 1. Escherichia coli can produce endotoxin due to its lipopolysaccharide component. 2. Salmonella enterica also produces endotoxin as part of its cell wall structure. 3. Pseudomonas aeruginosa is known to produce endotoxin as well. Therefore, all of these bacteria are capable of producing endotoxin, which can trigger an excessive immune response leading to septic shock. Other choices are incorrect because they do not cover all the bacteria mentioned in the question that are capable of producing endotoxin.
Question 6 of 9
The etiological agent of Q-fever is:
Correct Answer: B
Rationale: The correct answer is B: Coxiella burnetii. Q-fever is caused by the bacterium Coxiella burnetii. It is not caused by viruses like Bunyaviridae or Filoviridae. Rickettsia conorii causes Mediterranean spotted fever, not Q-fever. Coxiella burnetii is the only bacterium among the choices known to be the etiological agent of Q-fever.
Question 7 of 9
A patient with suspicion on epidemic typhus was admitted to the hospital. Some arachnids and insects have been found in his flat. Which of them may be a carrier of the pathogen of epidemic typhus?
Correct Answer: A
Rationale: The correct answer is A: Lice. Lice, specifically body lice (Pediculus humanus corporis), are known carriers of the pathogen Rickettsia prowazekii, which causes epidemic typhus. Body lice are commonly found in unsanitary conditions and can transmit the bacteria through their bites. Spiders (choice B), bed-bugs (choice C), and cockroaches (choice D) are not known vectors of epidemic typhus. Spiders are predators that do not transmit diseases to humans, while bed-bugs and cockroaches are associated with other health issues but not epidemic typhus transmission.
Question 8 of 9
In a bacteriological laboratory some bacterial smears had to be stained by Gram's method. For this purpose the following reagents were prepared: gentian violet, Lugol's solution, aqueous fuchsin solution. What other reagent is required?
Correct Answer: A
Rationale: The correct answer is A: 96% ethanol. In Gram's staining method, after applying gentian violet, Lugol's solution, and aqueous fuchsin, the next step is to use a decolorizing agent like 96% ethanol to wash away the excess stain from the Gram-negative bacteria. This step is crucial as it helps differentiate between Gram-positive and Gram-negative bacteria based on their cell wall properties. The other choices are incorrect because sulfuric acid is not used in Gram's staining method, methylene blue is typically used in other staining techniques like the simple stain, and carbolic fuchsin is not a standard reagent in the Gram's staining process.
Question 9 of 9
In which of the following especially dangerous infections, the respiratory tract is not damaged:
Correct Answer: D
Rationale: The correct answer is D, Cholera. Cholera is caused by the bacterium Vibrio cholerae and primarily affects the intestines, leading to severe watery diarrhea and dehydration. It does not damage the respiratory tract. Choice A, Tularemia, affects the respiratory tract and other organs. Choice B, Plague, can cause respiratory symptoms like cough and difficulty breathing. Choice C, Anthrax, can affect the respiratory tract if inhaled in its spore form.