Microbiology Chapter 14 Test Bank

Correct Answer: A

Rationale: The correct answer is A: Lamblia. The description matches the characteristics of Giardia lamblia - a protozoan parasite that causes giardiasis. The piriform bodies, 4 pairs of filaments, and two symmetrically located nuclei are specific to Giardia lamblia. It is important to differentiate it from the other choices. Dysentery ameba (choice B) typically has a single nucleus and lacks the specific characteristics described. Trichomonas (choice C) is a flagellated protozoan with different morphology and does not match the given description. Intestinal ameba (choice D) such as Entamoeba histolytica usually has a single nucleus and different body shape compared to the described organism.

Correct Answer: C

Rationale: The correct answer is C because chills, fever, and loss of consciousness are not typical symptoms of botulism. Botulism is characterized by descending, flaccid paralysis (choice A), dry mouth, difficulty swallowing, and speaking (choice B), and blurred vision, diplopia (choice D). These symptoms result from the neurotoxin produced by Clostridium botulinum, leading to muscle weakness and paralysis. Chills, fever, and loss of consciousness are more commonly associated with infections or other conditions, not botulism.

Correct Answer: A

Rationale: The correct answer is A because Staphylococcus aureus can develop resistance to penicillin over time due to the production of beta-lactamase enzymes. This resistance mechanism makes it no longer susceptible to penicillin. The other choices are correct: B) S. aureus can produce beta hemolysis, C) it produces various toxins like hemolysins, leucocidins, and enterotoxins, and D) it shows a positive catalase reaction due to the presence of catalase enzyme that converts hydrogen peroxide to water and oxygen.

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.

Correct Answer: A

Rationale: The correct answer is A: Mononuclears, T-lymphocytes and lymphokines. In a Mantoux test reaction, mononuclear cells, mainly T-lymphocytes, are activated by the injected allergen. These T-lymphocytes release lymphokines, leading to the observed swelling, hyperaemia, and tenderness. Granulocytes and IgG (choice B) are not the primary players in this type of delayed hypersensitivity reaction. Plasmatic cells (choice C) are not involved in the initial stages of this reaction. B-lymphocytes and IgM (choice D) are not the key components in the Mantoux test reaction.