microbiology chapter 1 test bank

Correct Answer: D

Rationale: The correct answer is D: salmonellosis. Zoonotic diseases are those that can be transmitted from animals to humans. Salmonella is not directly transmitted from animals to humans, instead, it is typically transmitted through contaminated food or water. Brucellosis (A), undulant fever (B), and plague (C) are all zoonotic diseases that can be directly transmitted from animals to humans through various means. Therefore, salmonellosis does not fit the definition of a zoonotic disease, making it the correct answer.

Correct Answer: C

Rationale: Step 1: Anthrax causative agent is Bacillus anthracis, which forms spores. Step 2: Spores are highly resistant structures that can survive for a long time. Step 3: These spores can germinate into active bacteria when conditions are favorable. Step 4: The presence of spores in the powder makes it dangerous even long after being mailed. Summary: A: Incorrect - Anthrax does not form a protein capsule. B: Incorrect - Anthrax does not form a polysaccharide capsule. C: Correct - Anthrax forms spores that are highly resistant. D: Incorrect - Anthrax does not form flagella.

Correct Answer: D

Rationale: The correct answer is D: Viscerotropic Leishmania. The presence of crescent-shaped bodies with pointed tips, blue cytoplasm, and red nuclei is characteristic of Leishmania species. Viscerotropic Leishmania causes visceral leishmaniasis, also known as kala-azar, which affects the internal organs. Toxoplasma typically presents as tachyzoites, not crescent-shaped bodies. Plasmodium malariae is a malaria parasite with different morphology. Dermatotropic Leishmania causes cutaneous leishmaniasis, not the visceral form indicated by the morphology described in the question.

Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani. The presence of Gram-positive rods with terminal spores resembling drumsticks indicates Clostridium tetani, the causative agent of tetanus. This bacterium forms spores at one end, giving it a drumstick appearance under the microscope. Clostridium perfringens (B) and Clostridium botulinum (D) do not have terminal spores. Bacillus anthracis (C) forms spores but typically appears as a square-ended or bamboo stick shape. Therefore, based on the microscopy findings, Clostridium tetani is the most likely microorganism responsible for the wound infection.

Correct Answer: A

Rationale: The correct answer is A: Shigella dysenteriae. It is the likely causative agent because it is a non-lactose-fermenting, Gram-negative rod commonly associated with severe diarrhea. Shigella dysenteriae specifically causes bacillary dysentery. Other choices are incorrect because: B: Escherichia coli is a lactose-fermenting bacterium commonly found in the gut and not typically associated with severe diarrhea. C: Salmonella typhi causes typhoid fever, not severe diarrhea. D: Proteus mirabilis is a urease-positive bacterium associated with urinary tract infections, not severe diarrhea.