Which of the following is used to test for bacterial antibiotic susceptibility?

Correct Answer: C

Rationale: The correct answer is C: Kirby-Bauer disk diffusion test. This test is used to determine the antibiotic susceptibility of bacteria by measuring the zone of inhibition around antibiotic-soaked paper disks. It helps identify which antibiotics are effective against the bacteria being tested. This test is crucial in guiding antibiotic treatment decisions. A: Gram stain is used to classify bacteria based on their cell wall composition and morphology, not for antibiotic susceptibility testing. B: Catalase test is used to differentiate between catalase-positive and catalase-negative bacteria, not for antibiotic susceptibility testing. D: Endospore stain is used to detect the presence of endospores in bacteria, not for antibiotic susceptibility testing.

Correct Answer: B

Rationale: The correct answer is B: protein synthesis. Bacterial ribosomes are responsible for translating messenger RNA into proteins through a process called translation. Ribosomes are composed of both protein and RNA molecules and facilitate the binding of transfer RNA to the messenger RNA to assemble the amino acids in the correct order to form a protein. DNA replication (A) is carried out by enzymes such as DNA polymerase, not ribosomes. Cell wall synthesis (C) is a process involving enzymes that build the structure of the cell wall in bacteria. RNA splicing (D) is a eukaryotic process that involves removing introns from pre-mRNA molecules, which is not a function of bacterial ribosomes.

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: 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: Co-trimoxazole. This drug combination is the first-line treatment for toxoplasmosis due to its efficacy against Toxoplasma gondii. Co-trimoxazole consists of sulfamethoxazole and trimethoprim, which work synergistically to inhibit bacterial and protozoal folate synthesis, effectively treating toxoplasmosis. B: Itraconazole is an antifungal medication and not effective against toxoplasmosis. C: Mebendazole is an anthelmintic drug used for treating parasitic worm infections, not toxoplasmosis. D: Azidothimidine, also known as AZT, is used for treating HIV, not toxoplasmosis.

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: Kirby-Bauer disk diffusion test. This test is used to determine the antibiotic susceptibility of bacteria by measuring the zone of inhibition around antibiotic-soaked paper disks. It helps identify which antibiotics are effective against the bacteria being tested. This test is crucial in guiding antibiotic treatment decisions. A: Gram stain is used to classify bacteria based on their cell wall composition and morphology, not for antibiotic susceptibility testing. B: Catalase test is used to differentiate between catalase-positive and catalase-negative bacteria, not for antibiotic susceptibility testing. D: Endospore stain is used to detect the presence of endospores in bacteria, not for antibiotic susceptibility testing.

Correct Answer: C

Rationale: The correct answer is C because Rotaviruses are not a major cause of meningitis; they primarily cause gastroenteritis. This is because Rotaviruses infect the gastrointestinal tract, not the central nervous system. Choice A is incorrect because there is no specific antiviral therapy for Rotaviruses. Choice B is correct as Rotaviruses are indeed widespread globally. Choice D is correct as Rotaviruses are shed in large amounts in feces, contributing to their ability to spread easily.

Correct Answer: B

Rationale: The correct answer is B: Movement of the bacterial cell. Bacterial flagella are whip-like appendages that enable bacteria to move towards nutrients or away from harmful substances. This movement is essential for survival, dispersal, and colonization. Choice A is incorrect because attachment is primarily mediated by other structures like pili. Choice C is incorrect as protein synthesis occurs inside the cell and is not directly related to flagella. Choice D is incorrect as nutrient absorption is typically carried out through specific channels or transport systems, not by flagella.