microbiology a systems approach test bank

Correct Answer: C

Rationale: The correct answer is C: IgG. IgG is the only antibody that can cross the placenta due to its small size and unique structure, allowing it to provide passive immunity to the fetus. IgA is mainly found in mucosal secretions, IgM is too large to cross the placental barrier, and IgD plays a role in B cell activation but is not involved in placental transfer.

Correct Answer: C

Rationale: The correct answer is C: 10% of the infected men have no symptoms. This is true because gonorrhea can be asymptomatic in some individuals, leading to undiagnosed cases. Testicular pain and epididymal tenderness (choice A) are not typical symptoms of gonorrhea in men. Painful urination (choice B) may or may not be present. Purulent discharge (choice D) is a common symptom but not always present. Therefore, choice C is the most accurate statement regarding gonorrhea symptoms in men.

Correct Answer: A

Rationale: The Ziehl-Neelsen stain is specific for acid-fast bacteria like Mycobacterium tuberculosis. The bright red bacilli seen in the smear indicate the presence of acid-fast organisms, which is characteristic of Mycobacterium tuberculosis. Staphylococcus aureus, Clostridium tetani, and Escherichia coli are not acid-fast bacteria and would not be stained red using the Ziehl-Neelsen method. Therefore, the correct answer is A: Mycobacterium tuberculosis.

Correct Answer: A

Rationale: The correct answer is A: Dysenteric amoeba. This is because dysenteric amoebas can cause asymptomatic parasitosis, where a healthy person carries cysts that can infect others. Dysenteric amoebas are known to infect the intestines and can be transmitted through contaminated food or water. Choice B, Malarial plasmodium, causes malaria transmitted through mosquitoes. Choice C, Enteral trichomonad, causes diarrhea and is transmitted through contaminated water. Choice D, Dermatotropic leishmania, causes skin lesions and is transmitted through sandfly bites. These choices do not fit the scenario of asymptomatic parasitosis in public catering establishments.

Correct Answer: D

Rationale: The correct answer is D because all three choices, Clostridium botulinum, Morbillivirus morbillorum, and Clostridium tetani, can cause infections of the CNS. Clostridium botulinum can lead to botulism, affecting the nervous system. Morbillivirus morbillorum can cause measles, which can lead to encephalitis. Clostridium tetani can cause tetanus, affecting the central nervous system. Therefore, all three choices can cause infections of the CNS. Choices A, B, and C are incorrect individually because each pathogen can cause CNS infections.