medical microbiology test bank

Correct Answer: A

Rationale: The correct answer is A: Neisseria meningitidis. This bacterium is a Gram-negative diplococcus commonly associated with meningitis. The patient's symptoms of fever, headache, and neck stiffness are classic signs of meningococcal meningitis. Neisseria meningitidis is known to cause outbreaks in crowded settings. Streptococcus pneumoniae (Choice B) is a common cause of bacterial meningitis but typically appears as Gram-positive cocci. Haemophilus influenzae (Choice C) can also cause meningitis but is more commonly seen in unvaccinated children. Klebsiella pneumoniae (Choice D) is a Gram-negative bacterium but is not a typical causative agent of meningitis.

Correct Answer: A

Rationale: The correct answer is A: Treponema pallidum. This bacterium is responsible for causing syphilis due to its unique spiral shape and ability to penetrate mucous membranes. It is transmitted through sexual contact or from mother to fetus. Neisseria gonorrhoeae causes gonorrhea, Chlamydia trachomatis causes chlamydia, and Escherichia coli is a common bacterium in the gastrointestinal tract. Syphilis is distinct due to its characteristic symptoms and stages, making Treponema pallidum the correct choice.

Correct Answer: B

Rationale: The correct answer is B: Neisseria gonorrhoeae. This bacterium is known to cause gonorrhea, a sexually transmitted infection. Neisseria gonorrhoeae specifically infects the mucous membranes of the reproductive tract in both men and women. It is transmitted through sexual contact. Explanation of other choices: A: Chlamydia trachomatis is a bacterium that causes chlamydia, not gonorrhea. C: Mycoplasma genitalium is associated with non-gonococcal urethritis, not gonorrhea. D: Treponema pallidum is the bacterium that causes syphilis, not gonorrhea. Therefore, Neisseria gonorrhoeae is the correct answer based on its direct association with causing gonorrhea.

Correct Answer: B

Rationale: The correct answer is B: Malaria. Fever developing 2 weeks post-blood transfusion is characteristic of malaria due to the incubation period of the parasite. Trypanosomiasis presents earlier, amebiasis usually causes GI symptoms, and toxoplasmosis typically manifests with flu-like symptoms. Malaria is the most likely cause based on the timing and clinical presentation.

Correct Answer: A

Rationale: The correct answer is A: Tetanus. Tetanus is caused by the bacterium Clostridium tetani, which produces a neurotoxin leading to muscle stiffness, including trismus (restricted mouth opening). The patient's history of a stab wound increases the likelihood of tetanus infection due to the spores entering the body through the wound. Incorrect Choices: B: Brucellosis does not typically present with trismus and is more commonly associated with fever, joint pain, and fatigue. C: Whooping cough presents with severe coughing fits but does not cause trismus. D: Wound anaerobic infection may cause localized symptoms at the wound site but is less likely to cause trismus compared to tetanus.