Dermatitis, diarrhoea and dementia are characteristics of:

Correct Answer: D

Rationale: Step-by-step rationale for why D (Pellagra) is correct: 1. Dermatitis: Pellagra is characterized by skin rashes due to niacin deficiency. 2. Diarrhoea: Niacin deficiency in Pellagra affects the digestive system, leading to diarrhea. 3. Dementia: Niacin deficiency affects the brain, causing neurological symptoms like dementia. Summary of why other choices are incorrect: A: Dry beriberi is caused by thiamine (B1) deficiency, not niacin. B: Pyridoxine deficiency (vitamin B6) does not typically present with dermatitis, diarrhea, or dementia. C: Scurvy is caused by vitamin C deficiency and is characterized by bleeding gums, weakness, and fatigue, not the symptoms mentioned in the question.

Correct Answer: B

Rationale: The correct answer is B: Metastatic calcifications. Vitamin D3 can lead to hypercalcemia, causing calcium to deposit in soft tissues like blood vessels and kidneys, leading to metastatic calcifications. Choice A is incorrect because vitamin D deficiency, not excess, causes defective bone mineralization. Choice C is incorrect as vitamin D toxicity primarily affects calcium levels, not the liver. Choice D is incorrect as nephrolithiasis is more commonly associated with excess intake of calcium supplements, not vitamin D3.

Correct Answer: B

Rationale: Step 1: Plicamycin inhibits RNA synthesis in cancer cells, leading to myelosuppression. Step 2: Myelosuppression results in decreased production of blood cells, causing anemia, thrombocytopenia, and neutropenia. Step 3: Diarrhea is not a common adverse effect of plicamycin. Step 4: Nephrolithiasis and metastatic calcifications are not directly associated with plicamycin use.

Correct Answer: B

Rationale: The correct answer is B: Enlarged uptake of the drug by a microorganism. This is incorrect because mechanisms of bacterial resistance involve reducing the uptake of the drug (choice D), modifying the drug's target (choice C), and actively transporting the drug out of the microorganism or hydrolyzing it with enzymes (choice A). Enlarged uptake would actually make the bacteria more susceptible to the antimicrobial agent, not resistant.

Correct Answer: D

Rationale: The correct answer is D. Sulfonamides inhibit folic acid synthesis, which is essential for the growth of bacteria, Chlamydia, Actinomyces, and some protozoa. This mechanism makes them effective against all the mentioned microorganisms. Choice A is incorrect because it does not include protozoa. Choice B is incorrect because sulfonamides are effective against Actinomyces. Choice C is incorrect because sulfonamides are not effective against all protozoa.