Correct Answer: D

Rationale: The correct answer is D: Helicobacter pylori. Helicobacter pylori is a known bacterium associated with causing duodenal ulcers. The presence of Gram-negative curved bacteria in the biopsy along with a highly positive rapid urease test is characteristic of H. pylori infection. Vibrio cholerae causes cholera, not duodenal ulcers. Campylobacter fetus is associated with gastroenteritis, not duodenal ulcers. Acinetobacter baumannii is a nosocomial pathogen, not typically associated with duodenal ulcers. In summary, the unique combination of findings in this case points towards H. pylori as the most likely cause of the disease.

Correct Answer: B

Rationale: The correct answer is B: Campylobacter jejuni. This bacteria is commonly associated with foodborne illnesses due to its presence in undercooked poultry and unpasteurized milk. Campylobacteriosis is a leading cause of bacterial gastroenteritis. Streptococcus pneumoniae (A) causes pneumonia, not foodborne illnesses. Mycobacterium tuberculosis (C) causes tuberculosis, not foodborne illnesses. Haemophilus influenzae (D) can cause respiratory infections but is not commonly associated with foodborne illnesses.

Correct Answer: D

Rationale: The correct answer is D: Sporozoites. Sporozoites are the infective stage of Plasmodium for the female Anopheles mosquito. Here's the rationale: After being transmitted to a human host through a mosquito bite, the sporozoites travel to the liver where they mature and reproduce asexually as merozoites (not the infective stage for mosquitoes). The merozoites then infect red blood cells, leading to symptoms like fever, headache, and shivering. During the blood stage, some merozoites develop into male and female gametocytes, which are not infective to mosquitoes. When a mosquito bites an infected person, it ingests gametocytes, which then develop into male and female gametes and fuse to form ookinetes. Ookinetes develop into oocysts in the mosquito's gut, releasing sporozoites that migrate to the salivary glands, ready to infect a new human host when the mosquito bites

Correct Answer: A

Rationale: The correct answer is A: Tuberculin. In this clinical scenario, the patient presents with symptoms suggestive of tuberculosis, including chronic cough, night sweats, weight loss, and hemoptysis. The Mantoux test, also known as the tuberculin skin test, is used to screen for tuberculosis. Tuberculin, a purified protein derivative (PPD) derived from Mycobacterium tuberculosis, is injected intradermally. The test elicits a delayed-type hypersensitivity reaction in individuals who have been exposed to the organism in the past. A positive Mantoux test indicates exposure to tuberculosis and does not differentiate between active infection and prior exposure. Explanation for other choices: B: Measles - Measles is a viral infection that presents with a characteristic rash and fever, not consistent with the symptoms described in the case. C: Tetanus and diphtheria toxoids vaccine (Td) - Td vaccine is not used for tuberculosis screening and does not elicit

Correct Answer: C

Rationale: Rationale: Choice C is correct because immunomodulators can indeed be natural (e.g., cytokines) or artificial compounds (e.g., synthetic peptides). They work by modulating the immune response, enhancing or suppressing it as needed. Choice A is incorrect because immunomodulators can stimulate both humoral and cellular immune responses. Choice B is incorrect as isoniazid is primarily an antibiotic used to treat tuberculosis, not an immunomodulator. Choice D is incorrect because immunomodulators can have varying effects on the immune response, not just suppress it.