Microbiology An Evolving Science Test Bank

Correct Answer: D

Rationale: The correct answer is D: Amebiasis. The patient's symptoms of gastrointestinal disturbance and liver abscess are indicative of an infection with Entamoeba histolytica, the protozoan parasite responsible for amebiasis. The patient's travel history to an African country also increases the likelihood of contracting this disease, as it is more prevalent in tropical regions. Toxoplasmosis (A) is primarily associated with exposure to cat feces, Leishmaniasis (B) is transmitted through sandfly bites, and Malaria (C) is caused by Plasmodium parasites transmitted through mosquito bites. Therefore, these options are incorrect given the patient's presentation and travel history.

Correct Answer: A

Rationale: The correct answer is A: Lassa virus. The rationale is as follows: 1. Lassa virus is a member of the Arenaviridae family, known for causing Lassa fever. 2. Arenaviridae family includes viruses with a segmented genome and are transmitted through rodents. 3. Crimean-Congo hemorrhagic fever virus (Choice B) belongs to the Bunyaviridae family, not Arenaviridae. 4. Rabies virus (Choice C) belongs to the Rhabdoviridae family, not Arenaviridae. 5. Epstein-Barr virus (Choice D) belongs to the Herpesviridae family, not Arenaviridae. In summary, Lassa virus is the correct choice as it aligns with the characteristics of the Arenaviridae family, while the other choices belong to different virus families.

Correct Answer: A

Rationale: The correct answer is A: Pertussis toxoid. This is because pertussis toxoid is a component of the pertussis vaccine, which provides specific prophylaxis against pertussis by stimulating the immune system to produce antibodies against the bacteria causing the disease. Choice B, killed vaccine, is incorrect as it does not specify pertussis toxoid. Choice C, wide-spectrum antibiotics, is incorrect as antibiotics are used for treatment, not prophylaxis. Choice D, None of the above, is incorrect as pertussis toxoid is specifically used for prophylaxis of pertussis.

Correct Answer: C

Rationale: The correct answer is C because the case specifically mentions "enteropathogenic bacteria and viruses," indicating a focus on these specific microorganisms. Choice A is too broad and includes all bacteria, which is not specified in the case. Choice B mentions opportunistic pathogenic bacteria, which are not necessarily relevant to the case. Choice D specifies colibacilli, which may or may not be relevant to the case, but it is not as specific as choice C which clearly matches the information provided in the case.

Correct Answer: A

Rationale: The correct answer is A: Commensalism. In this relationship, the skin microflora benefits from the host without causing harm or benefitting it. This is evident in the mutualistic interaction where the microflora receive nutrients and a place to live, while the host remains unaffected. Choice B, Infection, is incorrect because it implies harm to the host. Choice C, Parasitism, is also incorrect as it involves one organism benefiting at the expense of the other. Choice D, No correct answer, is not applicable here as Commensalism accurately describes the relationship between the macroorganism and skin microflora.