ATI RN
microbiology an introduction test bank Questions
Question 1 of 5
The primary target of beta-lactam antibiotics is:
Correct Answer: C
Rationale: The primary target of beta-lactam antibiotics is cell wall synthesis. These antibiotics inhibit enzymes called penicillin-binding proteins, which are essential for building the bacterial cell wall. By disrupting cell wall synthesis, beta-lactam antibiotics weaken the cell wall, leading to bacterial cell lysis and death. Protein synthesis (Choice A), DNA replication (Choice B), and folic acid synthesis (Choice D) are not directly targeted by beta-lactam antibiotics, making them incorrect choices.
Question 2 of 5
Gram staining is used to differentiate bacteria based on:
Correct Answer: C
Rationale: The correct answer is C: cell wall composition. Gram staining differentiates bacteria based on the structure of their cell walls. It classifies bacteria into Gram-positive (thick peptidoglycan layer) and Gram-negative (thin peptidoglycan layer). This differentiation is crucial for identifying bacterial species and guiding treatment choices. Size and shape (choice A) are not specific to Gram staining. Presence of flagella (choice B) is related to bacterial motility, not Gram staining. Genetic material (choice D) is not directly assessed by Gram staining. Overall, the unique composition of the cell wall is the key factor in distinguishing bacteria through Gram staining.
Question 3 of 5
A child presented with foul-smelling diarrhea. Stool microscopy revealed trophozoites with two nuclei and flagella. 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. The trophozoites of Giardia lamblia have two nuclei and flagella, which are characteristic features seen on stool microscopy. The presence of these specific features helps differentiate Giardia lamblia from the other options. Entamoeba histolytica (B) typically presents with one nucleus and lacks flagella. Trichomonas vaginalis (C) is a sexually transmitted parasite with a different morphology. Balantidium coli (D) is a ciliated parasite, not flagellated like Giardia lamblia.
Question 4 of 5
A wound swab from a patient with severe tissue infection revealed Gram-positive rods in chains producing gas. The bacteria were spore-forming. What is the causative agent?
Correct Answer: A
Rationale: The correct answer is A: Clostridium perfringens. This bacterium is a Gram-positive rod that forms chains and produces gas due to its ability to ferment carbohydrates. It is also spore-forming, which helps it survive harsh conditions. Clostridium perfringens is commonly associated with severe tissue infections and gas gangrene. Choice B: Bacillus anthracis is also a spore-forming Gram-positive rod but is not typically associated with gas production or severe tissue infections. Choice C: Clostridium tetani is a spore-forming bacterium that causes tetanus, not severe tissue infections with gas production. Choice D: Pseudomonas aeruginosa is a Gram-negative bacterium and does not fit the description provided in the question.
Question 5 of 5
A patient presented with a painful, swollen lymph node, and bacteremia. A Gram-negative rod with a characteristic safety pin appearance was observed. What is the causative agent?
Correct Answer: A
Rationale: Step 1: Gram-negative rod with safety pin appearance indicates bipolar staining. Step 2: Yersinia pestis is a Gram-negative rod causing bubonic plague. Step 3: Y. pestis has bipolar staining due to its unique F1 capsule. Step 4: The swollen lymph node and bacteremia are consistent with bubonic plague. Step 5: Therefore, the correct answer is A: Yersinia pestis. Summary: - B: Clostridium tetani causes tetanus, not characterized by a safety pin appearance. - C: Brucella melitensis causes brucellosis, not characterized by a safety pin appearance. - D: Pasteurella multocida causes animal bites infections, not characterized by a safety pin appearance.