A patient with suspected community-acquired pneumonia (CAP) is empirically started on antibiotic therapy pending culture results. Which of the following antibiotic regimens provides appropriate coverage for typical bacterial pathogens commonly implicated in CAP?

Correct Answer: A

Rationale: The correct answer is A: Ceftriaxone and azithromycin. Ceftriaxone covers Streptococcus pneumoniae, the most common pathogen in CAP, while azithromycin covers atypical pathogens like Mycoplasma pneumoniae. Vancomycin and piperacillin/tazobactam (choice B) are not first-line treatments for CAP. Ampicillin-sulbactam and levofloxacin (choice C) cover some pathogens but not as comprehensively as ceftriaxone and azithromycin. Clindamycin and cefepime (choice D) do not provide adequate coverage for typical CAP pathogens.

Correct Answer: C

Rationale: The correct answer is C: Acquired von Willebrand syndrome. This condition is characterized by a defect in von Willebrand factor function, leading to prolonged bleeding time and mucocutaneous bleeding. Normal platelet count rules out Glanzmann thrombasthenia and Bernard-Soulier syndrome which are platelet disorders. Normal PT and aPTT rule out Hemophilia A, a coagulation factor deficiency. Acquired von Willebrand syndrome is the most likely cause based on the clinical presentation and laboratory findings.

Correct Answer: B

Rationale: The correct answer is B: Disseminated intravascular coagulation (DIC). In DIC, there is widespread activation of coagulation leading to consumption of clotting factors, resulting in prolonged PT and aPTT, low fibrinogen levels, and elevated D-dimer. This pattern matches the laboratory findings in the patient. In liver cirrhosis (choice A), there is a decrease in clotting factors synthesis, leading to prolonged PT but not aPTT. Hemophilia A (choice C) is a genetic disorder that affects specific clotting factors, typically leading to prolonged aPTT but not PT. Vitamin K deficiency (choice D) impairs the synthesis of clotting factors, leading to prolonged PT but not aPTT and low levels of factors II, VII, IX, and X.

Correct Answer: C

Rationale: The correct answer is C: Meningitis. The patient's symptoms of severe headache, photophobia, neck stiffness, nuchal rigidity, and positive Kernig and Brudzinski signs are classic signs of meningitis. Meningitis is an inflammation of the meninges surrounding the brain and spinal cord, leading to these specific neurological symptoms. Migraine headache (A) typically presents with a throbbing headache, nausea, and sensitivity to light and sound, but does not typically cause neck stiffness or positive meningeal signs. Cluster headache (B) is characterized by severe unilateral headache with autonomic symptoms like tearing or nasal congestion, but does not typically cause neck stiffness or positive meningeal signs. Subarachnoid hemorrhage (D) presents with sudden severe headache often described as "the worst headache of my life," and may cause neck stiffness, but typically does not present with photophobia or positive meningeal signs like Kernig and Brudzinski signs.

Correct Answer: D

Rationale: The correct answer is D: Subarachnoid hemorrhage. This condition presents with sudden-onset severe headache, vomiting, and altered mental status due to bleeding in the subarachnoid space. This type of hemorrhage is typically noncontrast-enhancing on imaging. A: Ischemic stroke does not typically present with sudden-onset severe headache and vomiting. B: Subdural hematoma usually presents with a slower onset of symptoms and often develops after head trauma. C: Intracerebral hemorrhage presents with focal neurological deficits rather than altered mental status and vomiting. In summary, based on the sudden onset of symptoms, imaging findings, and clinical presentation, subarachnoid hemorrhage is the most likely diagnosis in this case.