mcgraw hill microbiology test bank

Correct Answer: A

Rationale: The correct answer is A: cultivating on artificial media and biochemical identification. This method is appropriate for diagnosing listeriosis because it allows for the isolation and growth of Listeria species on selective media, followed by biochemical tests to confirm the identity. Serological diagnosis with ELISA (choice B) is not as specific for Listeria and may yield false positives. Choice C, serological diagnosis with agglutination hype Widal, is not typically used for listeriosis diagnosis. Cultivating in cell cultures (choice D) is not the primary method for diagnosing listeriosis as it is less specific compared to cultivating on artificial media and biochemical identification.

Correct Answer: A

Rationale: The correct answer is A: Picornaviridae. Picornaviruses, such as enteroviruses, are commonly found in the feces of infected individuals. Therefore, their presence in water indicates fecal contamination and the need for additional purification. B: Herpesviridae are not typically associated with fecal contamination. C: Flaviviridae are mainly transmitted through arthropods like mosquitoes, not fecal contamination. D: Retroviridae, including HIV, are not typically excreted in high levels in feces and are not indicators of fecal contamination.

Correct Answer: D

Rationale: The correct answer is D: Lamblia. The cysts described match the characteristics of Giardia lamblia, a protozoan parasite. Giardia cysts are oval-shaped, 50-60 microns in diameter, and contain 2 nuclei (macronucleus and micronucleus). Giardia is commonly found in contaminated water sources and can cause gastrointestinal illness in humans. Incorrect choices: A: Toxoplasma - Toxoplasma gondii is a parasite that causes toxoplasmosis, transmitted through ingestion of contaminated food or water, but its cysts do not match the description given in the question. B: Amoeba - Amoebas are single-celled organisms, but they do not typically form cysts with visible nuclei as described. C: Balantidium - Balantidium coli is a ciliated protozoan that can cause dysentery in humans, but its cysts do not

Correct Answer: D

Rationale: The correct answer is D: Fibers at the vertices of the icosahedron. Adenoviruses have fibers at the vertices of the icosahedron, which give them their distinctive pattern. These fibers help in attaching to host cells. Choices A, B, and C are incorrect because adenoviruses do not have a lipid envelope, helical capsid, or ssDNA. Adenoviruses have a non-enveloped icosahedral capsid and contain dsDNA. This makes choice D the correct answer as it specifically relates to the unique structural feature of adenoviruses.

Correct Answer: B

Rationale: The correct answer is B: ELISA test for IgM anti-HAV in serum and HAV-Ag in stools. This test is the most reliable for detecting acute hepatitis A infection because IgM antibodies are produced early in the infection, indicating an active infection. Detection of HAV antigen in stools also confirms active viral shedding. A: Western blot assay for IgG anti-HAV in serum is not the most reliable for acute infection detection as IgG antibodies are produced later in the infection and indicate past exposure or immunity. C: ELISA test for IgG anti-HAV in serum is not the most reliable for acute infection detection as IgG antibodies are produced later in the infection and indicate past exposure or immunity. D: None of the above is incorrect as option B is the most appropriate choice for detecting acute hepatitis A infection.