Microbiology An Evolving Science Test Bank

Correct Answer: A

Rationale: Rationale: 1. Chagas disease is caused by Trypanosoma cruzi. 2. Trypanosoma cruzi is transmitted by triatomine bugs. 3. On a blood smear stained with Romanovsky's method, Trypanosoma cruzi appears as trypomastigotes. 4. Toxoplasma gondii causes toxoplasmosis, not Chagas disease. 5. Leishmania donovani and Leishmania tropica cause different forms of leishmaniasis, not Chagas disease.

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: D

Rationale: The correct answer is D: Clostridium. Clostridium bacteria produce the neurotoxin responsible for botulism. Clostridium botulinum is specifically known for causing this disease. Staphylococcus (A), Klebsiella (B), and Salmonella (C) do not produce the neurotoxin associated with botulism. Staphylococcus typically causes skin infections, Klebsiella is often associated with pneumonia and urinary tract infections, and Salmonella is known for causing food poisoning. Therefore, the correct answer is Clostridium due to its specific association with botulism.

Correct Answer: A

Rationale: The correct answer is A because it specifies the commonly used parameters for autoclaving sterilization: 1.0 atm pressure, 120� C temperature, and 15-20 minutes duration. This combination ensures effective sterilization by providing the necessary heat and pressure for killing microorganisms. Rationale: 1. Pressure of 1.0 atm: Standard atmospheric pressure commonly used in autoclaving. 2. Temperature of 120� C: Optimal temperature for sterilization without causing damage to heat-sensitive materials. 3. Duration of 15-20 minutes: Time required for heat and pressure to penetrate and kill microorganisms effectively. Summary of Incorrect Choices: B: Incorrect temperature and duration, too high and long, may damage materials. C: Incorrect pressure and temperature, higher pressure and temperature not commonly used. D: Incorrect temperature, too high, can damage materials, and duration is longer than necessary.

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.