A subacute toxic effect occurs when the adverse drug effect occurs:

Correct Answer: C

Rationale: The correct answer is C: after repeated exposure for days. Subacute toxic effects typically manifest after a period of time that is longer than immediate (A) or acute (B) effects but shorter than chronic effects (D). This duration of days aligns with the definition of subacute, which refers to effects that occur gradually over a relatively short time frame. It is important to differentiate between the timing of toxic effects to accurately assess the potential harm caused by a substance. Choices A, B, and D are incorrect because they do not align with the characteristic time frame associated with subacute toxic effects.

Correct Answer: D

Rationale: The correct answer is D because during the incubation period of Salmonella Typhi infection, the bacteria multiply in the macrophages of the Peyer's patches and solitary follicles. This is supported by the fact that S. Typhi is an intracellular pathogen that targets the lymphoid tissues of the intestines. Macrophages in these areas serve as the primary host cells for the bacteria, allowing for their replication and evasion of the host immune response. Choices A, B, and C are incorrect because S. Typhi does not primarily multiply in the small intestine enterocytes, the lumen of the small intestine, or hepatocytes during the initial stages of infection.

Correct Answer: A

Rationale: The correct answer is A because it accurately describes the major morphological forms of bacteria. Cocci are spherical, rod-shaped bacteria are called bacilli, and curved bacteria are spirilla. Staphylococci, streptococci, and diplococci are specific types of cocci, not major morphological forms. Basicili and spiralis are not common morphological forms of bacteria. Option D is incorrect as the other choices do represent major morphological forms of bacteria.

Correct Answer: B

Rationale: The correct answer is B: Diarrhea. Brucellosis typically presents with symptoms such as arthralgia, headache, and undulating fever, but diarrhea is not a common symptom associated with the disease. Brucellosis is primarily characterized by systemic symptoms like fever, joint pain, and headache due to the bacterial infection. Diarrhea is more commonly seen in gastrointestinal infections rather than brucellosis. Therefore, the absence of diarrhea as a symptom in brucellosis helps in differentiating it from other diseases with similar clinical presentations.

Correct Answer: A

Rationale: The correct answer is A: Halophiles. Halophiles are bacteria that thrive in high-salinity environments due to their ability to tolerate high salt concentrations. They have adapted mechanisms to maintain osmotic balance and survive in such extreme conditions. Thermophiles (B) thrive in high-temperature environments, not high-salinity. Acidophiles (C) prefer acidic conditions, not high-salinity. Mesophiles (D) grow optimally at moderate temperatures and are not specifically adapted to high-salinity environments.

Correct Answer: B

Rationale: The correct answer is B because the main target of the toxin produced by Vibrio cholerae is the epithelial cells of the small intestine. This toxin, known as cholera toxin, binds to the surface of these cells and disrupts their normal function, leading to the characteristic watery diarrhea seen in cholera. The other choices are incorrect because macrophages are not the main target, RBCs are not directly affected by the toxin, and the stomach epithelial cells are not specifically targeted by Vibrio cholerae toxin.

Correct Answer: B

Rationale: The correct answer is B: Family Reoviridae. Reassortment of gene segments occurs in segmented viruses like Reoviruses. In Reoviridae, each segment encodes a specific protein, allowing for reassortment to generate new strains. Togaviridae (A) is a non-segmented virus, not capable of reassortment. Picornaviridae (C) and Paramyxoviruses (D) are also non-segmented viruses, limiting their ability for reassortment. Therefore, the correct choice is B due to the segmented nature of Reoviruses allowing for genetic reassortment.

Correct Answer: A

Rationale: The correct answer is A: 1 chromosome. Bacterial cells typically have a singular circular chromosome that contains their genetic material. This chromosome is essential for the cell's survival and contains all the necessary genetic information for its functions. Choices B, C, and D are incorrect because they refer to the chromosome numbers found in human cells (23 pairs or 46 individual chromosomes). Bacteria, being prokaryotic organisms, have a simpler genetic makeup compared to eukaryotic organisms like humans, hence they possess only one chromosome.

Correct Answer: C

Rationale: The correct answer is C: Escherichia coli. E. coli is the most common cause of acute cystitis. It typically presents with leukocytes and gram-negative bacilli in the urine. The green pigment production indicates pyocyanin, which is a characteristic of E. coli. Pseudomonas aeruginosa (A) can also produce green pigment, but it is less common in urinary tract infections. Proteus mirabilis (B) is associated with a swarming motility pattern on agar, not mucous colonies. Klebsiella pneumoniae (D) is associated with pneumonia and other respiratory infections, not cystitis.