ATI RN
microbiology an introduction 13th edition test bank Questions
Question 1 of 5
A blood culture from a patient with sepsis revealed Gram-positive cocci in clusters. The organism was catalase-positive and coagulase-negative. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus epidermidis. Step 1: Gram-positive cocci in clusters suggest staphylococci. Step 2: Catalase-positive and coagulase-negative narrows it down to Staphylococcus epidermidis, as it is catalase-positive and coagulase-negative. Staphylococcus aureus (B) is catalase-positive and coagulase-positive. Streptococcus pyogenes (C) is catalase-negative. Enterococcus faecalis (D) is catalase-negative and coagulase-negative.
Question 2 of 5
Which bacteria is known for its ability to resist heat and radiation?
Correct Answer: B
Rationale: The correct answer is B: Bacillus subtilis. Bacillus subtilis is known for its ability to resist heat and radiation due to its formation of endospores, which are highly resistant structures that protect the bacterium from harsh environmental conditions. This resilience allows Bacillus subtilis to survive in extreme environments where other bacteria cannot. Explanation of other choices: A: Escherichia coli is not known for its exceptional resistance to heat and radiation. C: Pseudomonas aeruginosa is not particularly resistant to heat and radiation compared to Bacillus subtilis. D: Clostridium perfringens is not as well-known for its heat and radiation resistance as Bacillus subtilis.
Question 3 of 5
A Gram-positive cocci in chains was isolated from a patient with a throat infection. The bacteria were catalase-negative and beta-hemolytic. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. Rationale: 1. Gram-positive cocci in chains: S. pyogenes is a Gram-positive cocci in chains. 2. Catalase-negative: S. pyogenes is catalase-negative. 3. Beta-hemolytic: S. pyogenes exhibits beta-hemolysis. Summary of other choices: B: Streptococcus pneumoniae is alpha-hemolytic and optochin-sensitive. C: Enterococcus faecalis is catalase-negative, but not typically beta-hemolytic. D: Staphylococcus aureus is catalase-positive and coagulase-positive.
Question 4 of 5
A patient with fever and chills had blood cultures revealing Gram-negative rods that were oxidase-positive and lactose non-fermenters. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. This is because Pseudomonas is a Gram-negative rod, oxidase-positive, and a lactose non-fermenter. The presence of fever and chills suggests a systemic infection, which is common with Pseudomonas. Salmonella typhi, Shigella dysenteriae, and Escherimalia coli are all Gram-negative rods but are typically lactose fermenters and do not match the characteristics described in the question.
Question 5 of 5
Which bacteria are commonly associated with foodborne illnesses?
Correct Answer: D
Rationale: The correct answer is D because all three bacteria - Salmonella enterica, Clostridium botulinum, and Escherichia coli - are commonly associated with foodborne illnesses. Salmonella causes gastroenteritis, Clostridium botulinum causes botulism, and E. coli can lead to severe food poisoning. Each bacterium has different mechanisms of causing illness, but all can be transmitted through contaminated food. Choices A, B, and C alone are incorrect because they do not encompass the full spectrum of bacteria commonly linked to foodborne illnesses.