An etiological cause of hospital-acquired infections could be

Correct Answer: D

Rationale: The correct answer is D because hospital-acquired infections can be caused by a variety of microorganisms, including opportunistic pathogens and obligate pathogens such as bacteria or viruses. Opportunistic microorganisms take advantage of weakened immune systems in hospital patients, while obligate pathogens are capable of causing infections in healthy individuals. Therefore, all the choices are correct in this context as they represent potential etiological causes of hospital-acquired infections.

Correct Answer: A

Rationale: The correct answer is A because immunity in syphilis is nonsterile, meaning that individuals who have been infected may still carry the bacteria and be capable of transmitting the disease. This is due to the ability of the bacterium causing syphilis, Treponema pallidum, to evade the immune system by hiding within host cells. Option B, antitoxic, is incorrect because syphilis is not caused by a toxin produced by the bacteria, but rather by the bacterium itself. Option C, humoral, is also incorrect as syphilis immunity involves both humoral (antibody-mediated) and cell-mediated immune responses, not solely humoral immunity. Option D is incorrect as it includes all three options, whereas in reality, the immunity in syphilis is primarily nonsterile.

Correct Answer: B

Rationale: The correct answer is B: It causes epidemic meningitis. Neisseria Meningitidis is a bacterium that can cause meningitis, an infection of the protective membranes covering the brain and spinal cord. This bacterium is known to cause outbreaks or epidemics of meningitis, especially in crowded or close-contact settings. The other choices are incorrect because: A: Neisseria Meningitidis does have a capsule, which helps it evade the immune system. C: Neisseria Meningitidis grows on selective media like Thayer-Martin agar, not differential media. D: Neisseria Meningitidis is a Gram-negative diplococcus, not a Gram-positive rod.

Correct Answer: A

Rationale: The correct answer is A because a soft chancre is a type of sexually transmitted infection caused by the bacterium Haemophilus ducreyi. It presents as a painless ulcer on the genitals. The other choices are incorrect. B is incorrect because STIs can enter the body through various routes, not only the urogenital tract mucosa. C is incorrect because immunity to syphilis is not lifelong; reinfection is possible. D is incorrect because STIs can occur in any country regardless of social status or hygiene levels.

Correct Answer: D

Rationale: Bacteriophages are viruses that infect bacteria, not living organisms. They do not reproduce through division, mitosis, or meiosis because they lack the cellular machinery for these processes. Instead, bacteriophages replicate by inserting their genetic material into a host bacterium and hijacking its cellular machinery to produce new viral particles. Therefore, the correct answer is D - None of them. Division and mitosis involve cellular division in living organisms, while meiosis is a specialized process for sexual reproduction in eukaryotic organisms, none of which apply to bacteriophages.