A patient has a suspected pneumonia. In his sputum there were revealed gram-positive diplococci, prolonged with the slightly pointed opposite ends. What microorganisms are revealed in the sputum?

Correct Answer: A

Rationale: Rationale: The description matches that of Streptococcus pneumoniae, which appears as gram-positive diplococci with slightly pointed opposite ends. Staphylococcus aureus, Neisseria gonorrhoeae, and Neisseria meningitidis do not match the specific characteristics described in the question. Staphylococcus aureus appears in grape-like clusters, while Neisseria species are typically seen as diplococci but lack the pointed shape described. Therefore, the correct answer is A: Staphylococcus aureus.

Correct Answer: A

Rationale: Rationale: The described attributes match those of Balantidium. The presence of cilia, oval shape with a narrowed front and wide back end, visible mouth, two nucleuses, and short vacuoles are all characteristic features of Balantidium. Balantidium is a ciliated protozoan parasite commonly found in the human intestine. The other choices can be eliminated based on specific characteristics: Lamblia lacks cilia and has a different shape, Dysenteric amoeba typically has a single nucleus, and Trichomonas does not have cilia or multiple nuclei. Therefore, based on the specific attributes described, the correct answer is Balantidium (Choice A).

Correct Answer: A

Rationale: The correct answer is A: Kitt-Tarozzi medium. This medium is specifically designed to culture Clostridium species, the causative agents of gas gangrene. Clostridium species are gram-positive bacilli that produce gas during their metabolism. Inoculating the material into Kitt-Tarozzi medium allows for the selective growth of Clostridium species, aiding in the confirmation of a gas gangrene diagnosis. Other choices are incorrect: B: Endo agar is used for the isolation of gram-negative enteric bacteria. C: Meat-peptone agar is a general-purpose medium and not specific for Clostridium species. D: Levine agar is used for the isolation of Salmonella and Shigella species, not Clostridium.

Correct Answer: C

Rationale: The correct answer is C: Adhesion and immune evasion. Bacterial capsules serve as a protective layer that aids in adhesion to surfaces and host cells, allowing bacteria to colonize and evade the immune system. This function is crucial for bacterial survival and pathogenicity. Choices A and D are incorrect because energy production and DNA replication are not primary functions of bacterial capsules. Choice B is incorrect because while bacterial capsules do provide some protection from desiccation, their primary function lies in adhesion and immune evasion.

Correct Answer: A

Rationale: The correct answer is A: Protozoa. Protozoa are eukaryotic microorganisms, meaning they have a true nucleus and membrane-bound organelles. This relates to the question as eukaryotes are organisms with complex cells containing these features. Viruses (B) are non-living entities that require a host cell to replicate, lacking cellular structures. Viroids (C) are smaller than viruses and consist of only RNA, lacking a protein coat. Prions (D) are misfolded proteins causing diseases but are not considered microorganisms nor do they have cellular structure. Thus, protozoa are the only eukaryotic microorganism group among the options.

Correct Answer: B

Rationale: The Gram stain differentiates bacteria based on cell wall structure. It classifies bacteria into Gram-positive (purple) and Gram-negative (pink) based on the presence of peptidoglycan in the cell wall. This method helps in identifying the bacterial species and determining appropriate treatment. Option A (Cell shape) is incorrect because the Gram stain focuses on cell wall composition, not cell shape. Option C (Flagella composition) is incorrect as the Gram stain does not assess flagella. Option D (Nutrient requirements) is incorrect as it does not relate to the purpose of the Gram stain.

Correct Answer: C

Rationale: The correct answer is C: Obligate anaerobes cannot tolerate oxygen. They lack the enzymes needed to detoxify reactive oxygen species generated in the presence of oxygen. This makes them unable to survive in oxygen-rich environments. Choice A is incorrect because obligate anaerobes do not require oxygen to survive. Choice B is incorrect because obligate anaerobes specifically require the absence of oxygen. Choice D is incorrect because obligate anaerobes cannot even tolerate low levels of oxygen.

Correct Answer: A

Rationale: The correct answer is Amebiasis. The patient's symptoms of abdominal pain, loose stools with mucus and blood, along with the presence of protozoa containing phagocytosed erythrocytes in stool analysis are indicative of Entamoeba histolytica infection. The size (30-40 microns) and pseudopodia characteristics match E. histolytica. Amebiasis commonly presents with dysentery, while Leishmaniasis (B) typically causes skin ulcers. Trichomoniasis (C) is a sexually transmitted infection, not associated with the described symptoms. Giardiasis (D) is characterized by foul-smelling diarrhea and steatorrhea, not bloody diarrhea as seen in this case.

Correct Answer: B

Rationale: The correct answer is B: rheumatic fever. Rheumatic fever is an inflammatory disease that can occur as a complication following a group A streptococcal infection. This is known as a post-streptococcal complication. It typically affects the heart, joints, skin, and brain. Endocarditis (choice A) is also a complication of streptococcal infections, but it is an infection of the heart valves, not an inflammatory disease like rheumatic fever. Nephritis (choice C) is inflammation of the kidneys and is not directly related to streptococcal infections. Cytomegalovirus (choice D) is a different viral infection and is not associated with streptococcal infections.