MD Infectious Disease and Microbiology 4

Question 1

A 30-year-old with sickle cell disease presents with fever and severe bone pain. Blood culture grows encapsulated gram-negative rods. Which organism is this patient uniquely susceptible to due to functional asplenia?

Accepted Answer

Salmonella species

Answer

Sickle cell patients with functional asplenia are uniquely susceptible to Salmonella osteomyelitis (and S. pneumoniae sepsis), because the spleen normally opsonizes these encapsulated organisms.

Question 2

A 22-year-old develops fever, severe headache, petechial rash, and nuchal rigidity. CSF shows >1000 WBCs (predominantly neutrophils), low glucose, and gram-negative diplococci. Which antibiotic regimen is most appropriate?

Accepted Answer

Ceftriaxone + dexamethasone

Answer

Neisseria meningitidis meningitis is treated with ceftriaxone; adjunctive dexamethasone reduces inflammation and is recommended before or with the first antibiotic dose to prevent complications.

Question 3

A 55-year-old pigeon handler develops progressive pneumonia with relative bradycardia (pulse-temperature dissociation), dry cough, and hyponatremia. CXR shows patchy infiltrates. Which organism causes this atypical pneumonia?

Accepted Answer

Legionella pneumophila

Answer

Legionella pneumophila causes Legionnaires' disease, characterized by relative bradycardia, hyponatremia, diarrhea, and pontiac fever-like prodrome; it grows in water-cooling systems and causes lobar pneumonia.

Question 4

A 45-year-old with AIDS (CD4 60 cells/μL) develops progressive bilateral visual loss described as 'pizza pie' fundus with perivascular hemorrhages and exudates. Which organism is responsible?

Accepted Answer

Cytomegalovirus

Answer

CMV retinitis is the most common ocular opportunistic infection in AIDS patients with CD4 <50, producing the classic 'pizza pie' or 'scrambled eggs' appearance with hemorrhagic necrosis on funduscopy.

Question 5

A 6-year-old develops red strawberry tongue, scarlatiniform rash, and perioral pallor. Throat swab grows beta-hemolytic group A streptococcus. Which complication can be prevented by treating with penicillin?

Accepted Answer

Rheumatic fever

Answer

Antibiotic treatment of group A streptococcal pharyngitis prevents acute rheumatic fever (but NOT post-streptococcal glomerulonephritis, which is not prevented by antibiotics).

MD - Doctor of Medicine Practice Test

MD - Doctor of Medicine Practice Test

MD Infectious Disease and Microbiology 4