ATI RN
microbiology an introduction 13th edition test bank Questions
Question 1 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 2 of 5
A Gram-negative, comma-shaped bacterium was isolated from a patient with cholera. What is the most likely microorganism?
Correct Answer: A
Rationale: The correct answer is A: Vibrio cholerae.
1. Vibrio cholerae is a Gram-negative, comma-shaped bacterium known to cause cholera.
2. Shigella dysenteriae causes dysentery, not cholera.
3. Salmonella typhi causes typhoid fever, not cholera.
4. Campylobacter jejuni causes gastroenteritis, not cholera.
Therefore, based on the symptoms presented and the characteristics of the bacterium, Vibrio cholerae is the most likely microorganism.
Question 3 of 5
Which of the following bacteria is associated with foodborne illnesses caused by contaminated water?
Correct Answer: A
Rationale:
Step 1: Vibrio cholerae is a bacterium known to cause cholera, a foodborne illness transmitted through contaminated water.
Step 2: Cholera outbreaks are often linked to unsanitary water sources, making Vibrio cholerae the correct choice.
Step 3: Clostridium difficile causes gastrointestinal infections, not typically associated with contaminated water.
Step 4: Mycobacterium tuberculosis causes tuberculosis, a respiratory disease, not related to foodborne illnesses.
Step 5: Neisseria gonorrhoeae is a sexually transmitted bacterium, not linked to foodborne illnesses from contaminated water.
Question 4 of 5
A 32-year-old patient who lives in the countryside consulted a doctor about a painful swelling and a fistula in the submandibular region. Examination revealed an infiltration with a fistula discharging thick pus and containing white granules. On dissection the infiltration tissues turned out to be dense, yellow-green and had honeycomb structure because of multiple abscesses. What is the most likely diagnosis?
Correct Answer: A
Rationale: The most likely diagnosis is Actinomycosis. This is because the patient's presentation of a painful swelling with a fistula containing white granules and yellow-green honeycomb-like tissue is classic for Actinomycosis. Actinomyces is a gram-positive anaerobic bacterium that forms sulfur granules in tissues. Tuberculosis (
B) typically presents with caseating granulomas, not sulfur granules. Leprosy (
C) presents with skin lesions and nerve damage, not characteristic of this case. Syphilis (
D) usually presents with painless ulcers and rash, not the painful swelling and fistula seen in this patient.
Question 5 of 5
The only bacteria that have sterols in their cytoplasmic membrane are:
Correct Answer: D
Rationale: The correct answer is D: Mycoplasma. Mycoplasma is the only bacteria among the choices that have sterols in their cytoplasmic membrane. This feature helps stabilize their membrane structure due to the lack of a cell wall. Legionella (
A), Bacillus (
B), and Rickettsia (
C) do not contain sterols in their cytoplasmic membrane. Legionella has a unique lipid composition, Bacillus has peptidoglycan in its cell wall, and Rickettsia is an intracellular parasite lacking sterols in its membrane.