Correct Answer: A

Rationale: The correct answer is A: Kitt-Tarozzi medium. This medium is specifically designed to culture Clostridium species, the causative agents of gas gangrene. Clostridium species are gram-positive bacilli that produce gas during their metabolism. Inoculating the material into Kitt-Tarozzi medium allows for the selective growth of Clostridium species, aiding in the confirmation of a gas gangrene diagnosis. Other choices are incorrect: B: Endo agar is used for the isolation of gram-negative enteric bacteria. C: Meat-peptone agar is a general-purpose medium and not specific for Clostridium species. D: Levine agar is used for the isolation of Salmonella and Shigella species, not Clostridium.

Correct Answer: B

Rationale: The correct answer is B: Salmonella enterica. Typhoid fever is caused by the bacterium Salmonella enterica serotype Typhi. This specific strain of Salmonella is responsible for typhoid fever, a serious illness characterized by high fever, abdominal pain, and diarrhea. Escherichia coli (choice A) is not the causative agent of typhoid fever. Shigella flexneri (choice C) causes bacillary dysentery, not typhoid fever. Staphylococcus aureus (choice D) can cause food poisoning but is not associated with typhoid fever.

Correct Answer: B

Rationale: The correct answer is B: rheumatic fever. Rheumatic fever is an inflammatory disease that can occur as a complication following a group A streptococcal infection. This is known as a post-streptococcal complication. It typically affects the heart, joints, skin, and brain. Endocarditis (choice A) is also a complication of streptococcal infections, but it is an infection of the heart valves, not an inflammatory disease like rheumatic fever. Nephritis (choice C) is inflammation of the kidneys and is not directly related to streptococcal infections. Cytomegalovirus (choice D) is a different viral infection and is not associated with streptococcal infections.

Correct Answer: C

Rationale: The correct answer is C: Contaminated wounds. Tetanus is caused by the bacterium Clostridium tetani, which enters the body through breaks in the skin such as wounds or cuts. The bacteria produce a toxin that affects the nervous system, leading to muscle stiffness and spasms. Ingestion of contaminated food (choice A) is not a mode of transmission for tetanus. Inhalation of droplets (choice B) is more relevant for respiratory infections. Direct physical contact (choice D) is not the primary mode of transmission for tetanus as the bacteria need a portal of entry such as a wound to cause infection.

Correct Answer: A

Rationale: The correct answer is A: Isoniazid and rifampicin. These drugs are considered first-line treatment for tuberculosis due to their high efficacy and low toxicity. Isoniazid targets the cell wall of the tuberculosis bacteria, while rifampicin inhibits RNA synthesis. They are recommended by WHO as the first choice for treating tuberculosis. Choice B (Penicillin and erythromycin) is incorrect because these antibiotics are not effective against tuberculosis bacteria. Choice C (Trimethoprim and third generation cephalosporins) is incorrect because they are not considered first-line drugs for tuberculosis treatment. Choice D (All the listed above can be used depending on their resistance profile) is incorrect because only isoniazid and rifampicin are universally recognized as first-line drugs for tuberculosis regardless of resistance profile.