ATI RN
microbiology an introduction 12th edition test bank Questions
Question 1 of 5
What differentiates facultative anaerobes from obligate anaerobes?
Correct Answer: B
Rationale: Facultative anaerobes can switch between aerobic and anaerobic metabolism based on oxygen availability. This flexibility enables them to grow in both oxygen-rich and oxygen-poor environments, making choice B correct. Choice A is incorrect because facultative anaerobes do not require oxygen for survival. Choice C is incorrect as obligate anaerobes cannot grow in the presence of oxygen. Choice D is incorrect because obligate anaerobes cannot tolerate any amount of oxygen.
Question 2 of 5
Gram-negative rods producing red colonies on Endo agar were isolated from a fecal sample. The bacteria were lactose-fermenting. What microorganism is likely responsible?
Correct Answer: A
Rationale: The correct answer is A: Escherichia coli. E. coli is a Gram-negative rod that ferments lactose, leading to red colonies on Endo agar. This bacterium is commonly found in the human gut and is known for its ability to ferment lactose. Salmonella and Shigella are also Gram-negative rods but do not ferment lactose, so they would not produce red colonies on Endo agar. Proteus is a Gram-negative rod that is not known for its lactose-fermenting ability and would not produce red colonies on Endo agar. Therefore, based on the characteristics provided, E. coli is the most likely microorganism responsible for the red colonies on Endo agar.
Question 3 of 5
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 4 of 5
A patient with fever, enlarged lymph nodes, and bacteremia was diagnosed with plague. The Gram-stained smear revealed bipolar-staining, Gram-negative rods. What is the causative agent?
Correct Answer: A
Rationale: The correct answer is A: Yersinia pestis. Y. pestis is the causative agent of plague, characterized by fever, enlarged lymph nodes, and bacteremia. The bipolar-staining, Gram-negative rods seen on Gram stain are typical of Y. pestis. Incorrect choices: B: Francisella tularensis causes tularemia, not plague. C: Brucella abortus causes brucellosis, not plague. D: Clostridium botulinum causes botulism, not plague. In summary, the key features of the patient's presentation and the Gram stain findings align with Yersinia pestis as the correct causative agent of plague.
Question 5 of 5
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.