A patient complains of frequent bowel movements and stool with blood admixtures ("raspberry jelly" stool). Microscopic examination revealed large mononuclear cells with absorbed red blood cells. What protozoon is this morphological structure typical for?

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This protozoon is responsible for causing amoebic dysentery, which presents with bloody diarrhea. The "raspberry jelly" appearance of stool is due to the presence of mucosal lining and blood. The large mononuclear cells with absorbed red blood cells are characteristic of the histopathology of Entamoeba histolytica infection. Giardia lamblia (B) causes watery diarrhea, not bloody stools. Campylobacter jejuni (C) is a bacterial pathogen associated with gastroenteritis, but does not typically cause bloody diarrhea. Toxoplasma gondii (D) causes toxoplasmosis, a systemic infection with symptoms such as fever and lymphadenopathy, but not bloody diarrhea.

Correct Answer: C

Rationale: The correct answer is C: Flagella. Flagella are the structures used for bacterial motility, allowing bacteria to move towards or away from stimuli. They are long, whip-like appendages that rotate to propel the bacteria. Fimbriae (A) are short, hair-like structures used for attachment, not movement. Capsules (B) are protective layers surrounding bacteria. Pili (D) are used for adherence and conjugation, not motility. In summary, flagella are specifically designed for bacterial movement, making them the correct choice.

Correct Answer: D

Rationale: The correct answer is D because Streptococci are Gram-positive bacteria, typically spherical in shape, and range from 0.5-1 µm in size. A is incorrect as streptococci are not rod-shaped and are usually smaller in size. B is incorrect as they are not Gram-negative and are not typically of such small size. C is incorrect as streptococci are not Gram-negative and are not usually rod-shaped. Thus, based on their characteristics, the correct answer is D.

Correct Answer: A

Rationale: The correct answer is A: Blockaders of protein synthesis because antibiotics in this group target bacterial ribosomes, preventing protein synthesis. This disrupts bacterial growth and replication. Choice B is incorrect as cell wall synthesis inhibitors target a different bacterial component. Choice C is incorrect as antibiotics do not alter bacterial cytoplasm. Choice D is incorrect as antibiotics do fall into different categories based on their mechanism of action.

Correct Answer: B

Rationale: The correct answer is B: Flagella. Flagella are whip-like appendages used by bacteria for movement. They rotate in a corkscrew motion to propel the bacteria through their environment. Pili (choice A) are hair-like structures used for attachment, not movement. Capsules (choice C) are protective layers around bacteria, not involved in movement. Fimbriae (choice D) are also used for attachment and biofilm formation, not for movement. Therefore, the correct choice is B as flagella are specifically adapted for bacterial motility.

Correct Answer: B

Rationale: The correct answer is B: Endoplasmic reticulum. Prokaryotic cells lack membrane-bound organelles like the endoplasmic reticulum, which is present in eukaryotic cells. Prokaryotes do possess ribosomes for protein synthesis (A), a chromosome (C) for genetic material, and peptidoglycan (D) in their cell walls. The absence of endoplasmic reticulum is a key characteristic that distinguishes prokaryotic cells from eukaryotic cells.

Correct Answer: A

Rationale: The correct answer is A: Itraconazole. Itraconazole is an antifungal medication commonly used to treat candidosis. It works by inhibiting the synthesis of ergosterol, a key component of fungal cell membranes. This action disrupts the integrity of the fungal cell membrane, leading to cell death. Griseofulvin (B) is primarily used to treat fungal infections of the skin and nails, not mucous membranes. Nitrofungin (C) is not commonly used for candidosis treatment. Amphotericin (D) is a potent antifungal medication but is typically reserved for severe or systemic fungal infections due to its potential side effects.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This pathogen is known to cause amoebic dysentery, characterized by diarrhea with bloody or mucoid stools. The presence of cysts with four nuclei in the stool microscopy is a characteristic feature of Entamoeba histolytica. Other choices are incorrect because Giardia lamblia typically presents with binucleate cysts, Balantidium coli is a ciliated protozoan, and Trichomonas hominis is a non-pathogenic parasite found in the human intestine.

Correct Answer: C

Rationale: The correct answer is C, both A and B. Clostridium botulinum and Bacillus anthracis are both capable of forming spores, which are a protective mechanism that allows them to survive harsh conditions. Clostridium botulinum causes botulism and forms spores in anaerobic environments, while Bacillus anthracis causes anthrax and forms spores in aerobic environments. Therefore, both choices A and B are correct. Choice D is incorrect as it contradicts the fact that both bacteria are capable of forming spores.