ATI RN
microbiology an introduction 12th edition test bank Questions
Question 1 of 9
A patient with chronic diarrhea had stool microscopy revealing flagellated protozoa with two nuclei. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a flagellated protozoan with two nuclei found in the stool. It commonly causes chronic diarrhea. The other choices are incorrect because B: Entamoeba histolytica causes dysentery, not chronic diarrhea; C: Trichomonas vaginalis is a sexually transmitted infection, not typically found in stool; D: Balantidium coli is a ciliated protozoan, not flagellated.
Question 2 of 9
The eukaryotes known for the presence of a macronucleus and a micronucleus are:
Correct Answer: C
Rationale: The correct answer is C: protozoans. Protozoans are eukaryotic organisms that possess both a macronucleus, responsible for general cell functions, and a micronucleus, involved in genetic processes like reproduction. Algae (choice A) typically have a single nucleus, fungi (choice B) lack distinct macronucleus and micronucleus structures, and slime molds (choice D) do not have the same nucleus organization as protozoans. Thus, protozoans are the only group among the choices that exhibit the specific characteristics of having both a macronucleus and a micronucleus.
Question 3 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 4 of 9
Which of the following is likely to be the most frequently used portal of entry for pathogens?
Correct Answer: C
Rationale: The correct answer is C: Respiratory tract. The respiratory tract is likely the most frequently used portal of entry for pathogens because it is constantly exposed to the external environment and has a large surface area lined with mucous membranes that can trap and facilitate the entry of pathogens. Additionally, the respiratory tract serves as a direct pathway for pathogens to reach the bloodstream and other organs. Skin (choice A) is a physical barrier that can prevent pathogen entry, while the gastrointestinal tract (choice B) has acidic pH and enzymes that can kill many pathogens. Conjunctiva (choice D) is a less common portal of entry compared to the respiratory tract due to its smaller surface area and protective mechanisms such as tears.
Question 5 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 6 of 9
A child with foul-smelling diarrhea had trophozoites with two nuclei and flagella identified in stool microscopy. What is the causative agent?
Correct Answer: A
Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a protozoan parasite that causes foul-smelling diarrhea with trophozoites having two nuclei and flagella in stool microscopy. The presence of flagella and two nuclei is characteristic of Giardia lamblia. Entamoeba histolytica (Choice B) causes amoebic dysentery with trophozoites containing ingested RBCs. Trichomonas vaginalis (Choice C) is a sexually transmitted protozoan causing vaginitis with a distinctive pear-shaped trophozoite. Balantidium coli (Choice D) is a ciliated protozoan causing diarrhea with trophozoites containing a single nucleus.
Question 7 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 8 of 9
Which of these is not a factor counteracting the mechanisms of the immune system:
Correct Answer: D
Rationale: The correct answer is D: Hyaluronidase synthesis. Hyaluronidase is an enzyme produced by some pathogens to break down hyaluronic acid in the extracellular matrix, aiding their spread. This action does not directly counteract the immune system's mechanisms. Antigenic heterogeneity and mimicry can evade immune recognition. IgA proteases degrade IgA antibodies, impairing mucosal immunity. Therefore, D is the only choice not directly involved in counteracting the immune system.
Question 9 of 9
Sterilization destroys all microorganisms including:
Correct Answer: C
Rationale: Sterilization refers to the complete elimination of all microorganisms, including their spores, which are the most resistant form of microbial life. Spores have a tough outer coating that protects them from harsh conditions, making them more difficult to destroy compared to vegetative cells, viruses, and protozoa. Therefore, the correct answer is C because sterilization targets and eliminates all forms of microorganisms, including spores. Choices A, B, and D are incorrect because sterilization goes beyond just targeting vegetative cells, viruses, or protozoa; it aims to eliminate all microorganisms present.