A patient with foul-smelling diarrhea had a stool sample showing large ciliated protozoa with a kidney-shaped macronucleus. What is the diagnosis?

Correct Answer: A

Rationale: The correct answer is A: Balantidiasis. The large ciliated protozoa with a kidney-shaped macronucleus described in the stool sample is consistent with Balantidium coli, the causative agent of balantidiasis. Balantidium coli is the only ciliated protozoan parasite that infects humans and presents with these specific characteristics. Giardiasis (B) is caused by Giardia intestinalis, which is flagellated, not ciliated. Amoebiasis (C) is caused by Entamoeba histolytica, which has an amoeboid shape, not ciliated. Trichomoniasis (D) is caused by Trichomonas vaginalis, which is a flagellated protozoan and does not have a kidney-shaped macronucleus. Hence, the correct diagnosis in this case is Balantidiasis.

Correct Answer: C

Rationale: Rationale: 1. Candida is a fungus commonly isolated from clinical specimens. 2. Sabouraud agar is the most suitable medium for Candida due to its low pH and high dextrose content. 3. Low pH inhibits bacterial growth, while dextrose promotes fungal growth. 4. Zeisler media, Chocolate agar, and Muller-Hinton agar are not specific for fungal isolation. Summary: - Zeisler media is used for anaerobic bacteria. - Chocolate agar is used for fastidious organisms like Haemophilus. - Muller-Hinton agar is for antibiotic susceptibility testing, not fungal isolation.

Correct Answer: C

Rationale: The correct answer is C (60 years) because as individuals age, their immune system weakens, making them more susceptible to infectious diseases. Around the age of 60, people are more likely to succumb to infections, leading to a higher mortality rate. Choices A, B, and D are incorrect because they are younger ages, and the likelihood of infectious diseases causing a significant proportion of deaths increases with age.

Correct Answer: A

Rationale: The correct answer is A: Giardia lamblia. Giardia is a flagellated protozoa with two nuclei, causing diarrhea. It is commonly found in contaminated water sources. Entamoeba histolytica (B) causes amoebic dysentery with trophozoites in stool. Trichomonas vaginalis (C) causes sexually transmitted infections, not diarrhea. Balantidium coli (D) is a ciliated protozoa causing dysentery with ciliated trophozoites. Therefore, Giardia lamblia is the most likely causative agent in this case.

Correct Answer: B

Rationale: The correct answer is B because peritrichous bacteria have flagella distributed all over their surface, allowing them to move in various directions. Choice A is incorrect because bacteria with a single flagellum at one pole are called monotrichous. Choice C is incorrect as bacteria with a single flagellum at each pole are known as amphitrichous. Choice D is incorrect because peritrichous bacteria have multiple flagella all over their surface, not limited to one or both poles.

Correct Answer: A

Rationale: The correct answer is A: Trichomonads. Trichomonads are pear-shaped protozoa, typically 6-13 micrometers long, with one nucleus, undulating membrane, and four flagella at the front. These characteristics match the description provided in the question. Trichomonads are commonly found in oral cavities and can cause gum infections like periodontosis. Summary: - B: Leishmania - Leishmania is a flagellated protozoan responsible for Leishmaniasis, not typically found in the oral cavity. - C: Amoebae - Amoebae are not pear-shaped and do not have the specific characteristics described in the question. - D: Balantidia - Balantidia are ciliated protozoa, not flagellated like trichomonads, and are not typically associated with gum infections.

Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani. Clostridium tetani is responsible for causing tetanus by producing a neurotoxin called tetanospasmin. This neurotoxin blocks inhibitory signals in the central nervous system, leading to muscle spasms and stiffness characteristic of tetanus. Clostridium perfringens (B) causes gas gangrene, Streptococcus pyogenes (C) causes strep throat, and Escherichia coli (D) can cause gastrointestinal infections but not tetanus. Therefore, based on the specific pathogen and its mechanism of action, Clostridium tetani is the correct answer.

Correct Answer: D

Rationale: The correct answer is D because Borrelia burgdorferi cannot be detected with Giemsa stain. Giemsa stain is commonly used to visualize blood smears for malaria parasites but is not effective for Borrelia burgdorferi detection. A: Borrelia burgdorferi can be cultivated on blood agar - This is correct. Borrelia burgdorferi can be grown in culture on a special medium like Barbour-Stoenner-Kelly (BSK) agar. B: Borrelia burgdorferi is flexible, motile spirochete - This is correct. Borrelia burgdorferi is a spiral-shaped bacterium that moves using a corkscrew motion. C: Borrelia burgdorferi is transmitted by arthropods- ticks - This is correct. Borrelia burgdorferi is primarily transmitted to humans through the bite of infected ticks, particularly Ixodes

Correct Answer: A

Rationale: The correct answer is A: spleen. The spleen is not a component of the gastrointestinal tract; it is part of the lymphatic system. The pharynx, esophagus, and stomach are all part of the gastrointestinal tract responsible for digestion and absorption of food. The spleen's main functions include filtering blood, storing blood cells, and supporting the immune system, making it unrelated to the digestive process.