microbiology a systems approach test bank -Nurselytic

Correct Answer: A

Rationale: The correct answer is A: Mycobacterium tuberculosis. This bacterium is responsible for causing tuberculosis, as it has unique characteristics that allow it to infect the lungs and evade the immune system, leading to a chronic infection. Mycobacterium tuberculosis is a slow-growing, acid-fast bacterium that can survive and replicate within macrophages, causing the characteristic granulomas seen in tuberculosis.

Choice B, Escherichia coli, is a common gut bacterium and is not responsible for tuberculosis.
Choice C, Clostridium botulinum, causes botulism, not tuberculosis.
Choice D, Salmonella enterica, causes food poisoning, not tuberculosis.

Correct Answer: A

Rationale: The correct answer is A: Amebiasis. Amebiasis is caused by the parasite Entamoeba histolytica, presenting with symptoms like acute abdominal pain, bloody diarrhea with mucus, and inconstant shape organisms seen in fecal smear. The presence of erythrocytes supports the diagnosis due to the parasite's ability to invade intestinal mucosa causing bleeding.
Choice B (Lambliasis) presents with different symptoms like steatorrhea and fatigue.
Choice C (Schistosomiasis) is mainly associated with liver and urinary symptoms.
Choice D (Intestinal trichomoniasis) commonly presents with watery diarrhea and does not typically cause bloody stools.
Therefore, based on the patient's symptoms and fecal smear findings, Amebiasis is the most likely diagnosis.

Correct Answer: B

Rationale: The correct answer is B: Mycobacterium tuberculosis. Mycobacterium tuberculosis is the bacteria responsible for causing tuberculosis. This bacterium has unique cell wall components that make it resistant to the body's immune defenses, allowing it to survive and multiply within the host. Streptococcus pyogenes (
Choice
A), Escherichia coli (
Choice
C), and Bacillus anthracis (
Choice
D) are not associated with tuberculosis. Streptococcus pyogenes is known for causing strep throat and skin infections, Escherichia coli is commonly involved in gastrointestinal infections, and Bacillus anthracis causes anthrax.

Correct Answer: C

Rationale: The correct answer is C: Vibrio. Cholera is caused by Vibrio cholerae bacteria. These bacteria produce a toxin that causes severe diarrhea and dehydration. Escherichia (choice
A) and Salmonella (choice
B) are known for causing other types of gastrointestinal infections but not cholera. Acinetobacter (choice
D) typically causes respiratory infections, not gastrointestinal illnesses like cholera.
Therefore, the correct choice is Vibrio as it is specifically associated with cholera.

Correct Answer: C

Rationale: The correct answer is C: Thick peptidoglycan layer. Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain during Gram staining. This thick layer is a key characteristic feature that helps differentiate Gram-positive bacteria from Gram-negative bacteria.


Rationale:
1. Gram-positive bacteria retain the crystal violet stain due to their thick peptidoglycan layer.
2. This thick layer provides structural support and protection to the cell.
3. Gram-positive bacteria lack an outer membrane, which is a feature of Gram-negative bacteria (
Choice
A).
4. Thin peptidoglycan layer is a characteristic of Gram-negative bacteria, not Gram-positive (
Choice
B).
5. Presence of LPS (lipopolysaccharide) is a feature of Gram-negative bacteria, not Gram-positive (
Choice
D).

In summary, the presence of a thick peptidoglycan layer is a characteristic feature of Gram-positive