ATI RN
microbiology an introduction 12th edition test bank Questions
Question 1 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 2 of 5
The process in which bacteria take up foreign DNA from the environment is called:
Correct Answer: A
Rationale: The correct answer is A: Transformation. During transformation, bacteria take up foreign DNA from the environment and incorporate it into their own genetic material. This process allows for genetic diversity and adaptation. Transduction (B) involves transfer of DNA via a virus, conjugation (C) involves direct transfer of DNA between bacterial cells, and binary fission (D) is a form of asexual reproduction in bacteria. Transformation is the only process specifically related to bacteria taking up foreign DNA.
Question 3 of 5
A patient with diarrhea had stool microscopy revealing large, oval protozoa with a single nucleus and four flagella. What is the most likely causative agent?
Correct Answer: A
Rationale: Step 1: Large, oval protozoa with a single nucleus and four flagella indicate Giardia lamblia. Step 2: Giardia lamblia is a flagellated protozoan causing diarrhea. Step 3: It has a distinct appearance under microscopy. Step 4: Entamoeba histolytica causes dysentery with no flagella. Step 5: Balantidium coli is a ciliated protozoan with a larger size. Step 6: Trichomonas vaginalis lacks a cyst stage and causes genitourinary infections.
Question 4 of 5
A patient with a productive cough and fever had a Gram-positive cocci isolated from a sputum sample. The bacteria were catalase-positive and coagulase-negative. What is the likely microorganism?
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus epidermidis. 1. Gram-positive cocci suggest a staphylococcal species. 2. Catalase-positive indicates it belongs to the Staphylococcus genus. 3. Coagulase-negative rules out Staphylococcus aureus. 4. Staphylococcus epidermidis is a common cause of infections in immunocompromised patients. Summary: - B: Staphylococcus aureus is coagulase-positive. - C: Streptococcus pneumoniae is a Gram-positive diplococci. - D: Neisseria meningitidis is a Gram-negative diplococci.
Question 5 of 5
Which bacteria produce a toxin that inhibits protein synthesis?
Correct Answer: A
Rationale: The correct answer is A: Shigella dysenteriae. This bacteria produces the Shiga toxin, which inhibits protein synthesis by interfering with the ribosomes. Shigella dysenteriae causes severe gastrointestinal illness. The other choices, B: Clostridium botulinum, produces a neurotoxin that blocks neurotransmitter release. C: Streptococcus pneumoniae causes pneumonia and other respiratory infections. D: Mycobacterium tuberculosis causes tuberculosis by infecting the lungs. Thus, based on the toxin production and mode of action, Shigella dysenteriae is the correct answer.