microbiology chapter 14 test bank

Correct Answer: D

Rationale: The correct answer is D because a fourfold increase in titer in the second serum sample indicates a significant rise in specific antibodies, which is crucial for diagnosing viral infections accurately. This increase is considered significant in serologic reactions as it shows a strong antibody response to the virus. A: A threshold increase may not be substantial enough to confirm a diagnostic antibody response. B: Dismissing the increase in titer would overlook important diagnostic information. C: A twofold increase may not be as indicative of a strong antibody response compared to a fourfold increase.

Correct Answer: A

Rationale: The correct answer is A: Ascoli ring test. Agglutination reaction in the Ascoli ring test is characterized by the formation of a visible ring at the interface of antigen and antibody. This reaction specifically tests for the presence of specific antibodies against antigens in serum, indicating a recent or current infection. The other options, Western blot, ELISA, and Reaction type Gruber, do not involve the agglutination reaction. Western blot and ELISA are immunoassay techniques that detect specific antibodies or antigens, while Reaction type Gruber is not a recognized method in immunology. Therefore, the Ascoli ring test is the correct choice for a test involving agglutination reaction.

Correct Answer: B

Rationale: The correct answer is B: mycorrhizae. Mycorrhizae are symbiotic fungi that form a mutualistic relationship with plant roots, aiding in the absorption of minerals and water. They enhance the plant's nutrient uptake capacity, promoting plant growth and health. Decomposers (A) break down dead organic matter, yeasts (C) are single-celled fungi used in fermentation, and molds (D) are fungi that grow in multicellular filaments. These options do not specifically assist plant roots in mineral and water absorption like mycorrhizae do.

Correct Answer: A

Rationale: Correct Answer: A Rationale: 1. Enteropathogenic E. coli (EPEC) 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.

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.