ATI RN
microbiology an introduction tortora test bank Questions
Question 1 of 5
A 35-year-old patient with a severe respiratory infection had sputum that showed Gram-negative, comma-shaped bacteria. What is the likely causative agent?
Correct Answer: C
Rationale: The correct answer is C: Campylobacter jejuni. This bacterium is Gram-negative and comma-shaped, commonly causing respiratory infections. Vibrio cholerae (A) causes cholera, not respiratory infections. Shigella dysenteriae (B) causes dysentery, not respiratory infections. Helicobacter pylori (D) is associated with gastric ulcers, not respiratory infections. Therefore, Campylobacter jejuni is the most likely causative agent based on the given information.
Question 2 of 5
A patient presented with fever and cough. A sputum sample stained by Gram's method revealed Gram-positive diplococci with a capsule. What is the likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. The presence of Gram-positive diplococci with a capsule is characteristic of S. pneumoniae. This bacterium is a common cause of pneumonia, especially in patients with fever and cough. It is also known for causing infections such as otitis media and sinusitis. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically form diplococci or have a capsule. Neisseria meningitidis (C) is a Gram-negative diplococcus commonly associated with meningitis, not pneumonia. Klebsiella pneumoniae (D) is a Gram-negative rod, not a diplococcus, and is more commonly associated with pneumonia in immunocompromised patients.
Question 3 of 5
Which bacteria produce exotoxins that can cause severe dehydration and diarrhea?
Correct Answer: A
Rationale: The correct answer is A: Vibrio cholerae. This bacterium produces cholera toxin, an exotoxin that causes severe dehydration and diarrhea by increasing the secretion of electrolytes and water in the intestines. Vibrio cholerae is the causative agent of cholera, a disease characterized by profuse watery diarrhea. Choice B, Clostridium tetani, produces tetanospasmin causing tetanus, not dehydration or diarrhea. Choice C, Escherichia coli, can cause diarrhea but rarely severe dehydration. Choice D, Shigella dysenteriae, produces Shiga toxin leading to bloody diarrhea, not severe dehydration.
Question 4 of 5
A wound infection culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the most likely causative agent?
Correct Answer: A
Rationale: The most likely causative agent in this case is Staphylococcus epidermidis. This conclusion can be drawn based on the characteristics provided: Gram-positive cocci in clusters, catalase-positive, and coagulase-negative. Staphylococcus epidermidis fits all these criteria. Explanation of other choices: - Staphylococcus aureus: Typically coagulase-positive, so it does not match the characteristics given. - Streptococcus pyogenes: Gram-positive cocci in chains, not clusters. Also, it is catalase-negative. - Enterococcus faecalis: Gram-positive cocci in pairs or chains, not clusters. Additionally, it is catalase-negative. Therefore, Staphylococcus epidermidis is the most likely causative agent based on the provided characteristics.
Question 5 of 5
A patient with pneumonia had sputum cultured, revealing Gram-negative rods. The bacteria were lactose fermenters and produced green colonies on MacConkey agar. What is the most likely causative agent?
Correct Answer: A
Rationale: Rationale: 1. Gram-negative rods suggest Enterobacteriaceae family. 2. Lactose fermenters narrow down to E. coli. 3. Green colonies on MacConkey agar indicate acid production. 4. E. coli is a common cause of pneumonia. Therefore, the most likely causative agent is Escherichia coli. Other choices are incorrect as Klebsiella is non-lactose fermenter, Pseudomonas is oxidase-positive, and Proteus is non-lactose fermenter.