ATI RN
microbiology chapter 14 test bank Questions
Question 1 of 5
A wound culture from a patient with an infected ulcer 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 correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters, catalase-positive, and coagulase-negative characteristics indicate Staphylococcus species. Specifically, Staphylococcus epidermidis is a common skin commensal and a frequent cause of wound infections. Staphylococcus aureus is catalase-positive and coagulase-positive, making it less likely in this scenario. Streptococcus pyogenes and Enterococcus faecalis are both Gram-positive cocci but are catalase-negative, making them less likely causative agents.
Question 2 of 5
A patient with fever and diarrhea had a stool sample that revealed Gram-negative rods that fermented lactose. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Escherichia coli. E. coli is a Gram-negative rod that ferments lactose. It is a common cause of gastroenteritis presenting with fever and diarrhea. Salmonella typhi does not ferment lactose and causes typhoid fever. Shigella dysenteriae causes dysentery and does not ferment lactose. Proteus vulgaris does not typically cause gastroenteritis and is not known for lactose fermentation.
Question 3 of 5
Which of the following is a disease caused by a protozoan?
Correct Answer: B
Rationale: The correct answer is B:
Toxoplasmosis.
Toxoplasmosis is caused by the protozoan
Toxoplasma gondii. The rationale for this is that protozoa are single-celled organisms that can cause diseases in humans. Cat scratch disease (
A) is caused by a bacterium, Bartonella henselae. Relapsing fever (
C) is caused by the bacterium Borrelia recurrentis. Plague (
D) is caused by the bacterium Yersinia pestis.
Therefore, the only choice caused by a protozoan is toxoplasmosis, making it the correct answer.
Question 4 of 5
For enteropathogenic E. coli is true:
Correct Answer: A
Rationale:
Correct
Answer: A
Rationale:
1. Enteropathogenic E. coli (EPE
C) attach to enterocytes via a type III secretion system.
2. Once attached, they form attaching and effacing lesions on the microvilli, leading to microvillus destruction.
3. This mechanism allows EPEC to cause diarrhea by disrupting the normal absorptive function of the intestines.
Summary:
- B (They are invasive and produce enterotoxin) is incorrect because EPEC are non-invasive and do not produce enterotoxins.
- C (Cause disease clinically similar to bacterial) is vague and does not provide specific information about EPEC pathogenesis.
- D (None of the above) is incorrect as A is the correct explanation for EPEC pathogenicity.
Question 5 of 5
Some of the viruses have a cubic type of symmetry, which in the shape of
Correct Answer: D
Rationale: The correct answer is D: icosahedral structure. Icosahedral symmetry is common in viruses due to its efficient packing of genetic material. It consists of 20 equilateral triangular faces and 12 vertices. This symmetry allows viruses to have a stable structure and optimal capacity for encapsulating their genetic material.
A: Tetrahedral structure is incorrect as it consists of 4 faces and is not commonly found in viruses.
B: Hexahedral structure is incorrect as it consists of 6 faces and is not a common symmetry type in viruses.
C: Dodecahedral structure is incorrect as it consists of 12 faces and is not typically seen in viruses.
In summary, the icosahedral structure is the correct choice due to its stability, efficient packing, and common presence in viral structures compared to the other options.