ATI RN
microbiology test bank Questions
Question 1 of 9
A patient with diarrhea had stool culture revealing non-lactose-fermenting, Gram-negative rods. The bacteria were oxidase-positive and fermentative. What is the most likely causative agent?
Correct Answer: C
Rationale: The correct answer is C: Salmonella typhi. The patient's symptoms of diarrhea and the characteristics of non-lactose-fermenting, Gram-negative rods that are oxidase-positive and fermentative are consistent with Salmonella typhi. Salmonella typhi is the causative agent of typhoid fever, which presents with symptoms like diarrhea. Pseudomonas aeruginosa (choice A) is oxidase-positive but not fermentative. Escherichia coli (choice B) is both lactose-fermenting and oxidase-negative. Shigella dysenteriae (choice D) is oxidase-negative. Therefore, Salmonella typhi is the most likely causative agent based on the given information.
Question 2 of 9
A patient with pneumonia had sputum cultured revealing Gram-positive diplococci. The bacteria were catalase-negative and alpha-hemolytic. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. The given characteristics match this bacterium: Gram-positive diplococci, catalase-negative, and alpha-hemolytic. S. pneumoniae is a common cause of community-acquired pneumonia. Other choices are incorrect because Staphylococcus aureus is catalase-positive, Enterococcus faecalis is not alpha-hemolytic, and Klebsiella pneumoniae is not Gram-positive diplococci.
Question 3 of 9
Which of the following bacteria produce an endotoxin that causes fever and shock?
Correct Answer: D
Rationale: The correct answer is D (All of the above) as all three bacteria (Escherichia coli, Salmonella enterica, Neisseria meningitidis) produce endotoxins causing fever and shock. Endotoxins are lipopolysaccharides found in the outer membrane of Gram-negative bacteria and can trigger an immune response leading to fever and shock. Escherichia coli and Salmonella enterica are common causes of food poisoning and sepsis, while Neisseria meningitidis is responsible for meningococcal meningitis and septicemia. Therefore, all three choices are correct in producing endotoxins that can cause fever and shock.
Question 4 of 9
Which of the following bacteria is responsible for producing a neurotoxin that causes tetanus?
Correct Answer: B
Rationale: The correct answer is B: Clostridium tetani. Clostridium tetani produces tetanospasmin, a neurotoxin causing tetanus. It enters the body through wounds and affects the nervous system. A: Clostridium botulinum produces botulinum toxin causing botulism, not tetanus. C: Streptococcus pneumoniae causes pneumonia, not tetanus. D: Mycobacterium tuberculosis causes tuberculosis, not tetanus.
Question 5 of 9
What comes after class in the classification system?
Correct Answer: B
Rationale: The correct answer is B: Phylum. After class in the classification system comes phylum. The classification system starts with the broadest category, which is the kingdom, followed by phylum, class, order, family, genus, and species. Phylum is a higher level of classification than class, so it comes next in the hierarchy. Domain is a higher level than kingdom, and order is a lower level of classification than class. Therefore, the correct sequence is kingdom, phylum, class, order.
Question 6 of 9
The nucleocapsid of viruses consists of:
Correct Answer: C
Rationale: Step 1: The nucleocapsid is the structure containing the viral genome and the protein capsid. Step 2: The genome carries the genetic material of the virus. Step 3: The capsid is the protein coat that encloses and protects the viral genome. Step 4: Therefore, the correct answer is C: Genome and capsid. Summary: A: Capsid and spikes - Incorrect, spikes are not part of the nucleocapsid. B: Genome and envelop - Incorrect, the envelop is not part of the nucleocapsid. D: Capsid and envelope - Incorrect, the envelope is not part of the nucleocapsid.
Question 7 of 9
A smear of dental plaque revealed unicellular organisms with pseudopodia and ingested white blood cells. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Entamoeba gingivalis. This organism matches the description provided in the question - unicellular with pseudopodia and ingested white blood cells, commonly found in dental plaque. Entamoeba gingivalis is known to inhabit the oral cavity and is associated with periodontal disease. Trichomonas vaginalis, Giardia lamblia, and Balantidium coli do not match the characteristics mentioned in the question and are not typically found in the oral cavity.
Question 8 of 9
During a microscopy session, students examined sputum samples stained using Gram's method. Purple-stained diplococci with a capsule were observed. What microorganism is most likely present?
Correct Answer: A
Rationale: Step-by-step rationale: 1. Purple-stained diplococci suggest Gram-positive cocci. 2. Capsule presence is a characteristic of Streptococcus pneumoniae. 3. S. pneumoniae is known to form diplococci arrangements. 4. Therefore, the microorganism most likely present is Streptococcus pneumoniae. Summary: - B: Klebsiella pneumoniae is a Gram-negative rod, not a cocci. - C: Neisseria meningitidis is a Gram-negative diplococcus, not a capsule producer. - D: Escherichia coli is a Gram-negative rod, not a cocci or capsule producer.
Question 9 of 9
The proteins implicated in spongiform encephalopathy are __________.
Correct Answer: A
Rationale: The correct answer is A: prions. Prions are misfolded proteins that can cause spongiform encephalopathy by inducing normal proteins to misfold as well. Prions lack genetic material, distinguishing them from viruses (B), bacteria (C), and fungi (D), which all contain genetic material and cannot directly cause spongiform encephalopathy through protein misfolding.