PANCE Infectious Disease 2 — Questions and Answers
Question 1: A 55-year-old diabetic patient presents with severe right ear pain, purulent otorrhea, and facial nerve palsy. CT scan shows bony erosion at the skull base. Which organism is responsible for this condition?
- Staphylococcus aureus
- Streptococcus pneumoniae
- Pseudomonas aeruginosa (Correct answer)
- Aspergillus fumigatus
Correct answer: Pseudomonas aeruginosa
Malignant (necrotizing) external otitis in diabetics is almost exclusively caused by Pseudomonas aeruginosa, which can extend to cause skull base osteomyelitis and cranial nerve palsies.
Question 2: A 22-year-old college student presents with fever, pharyngitis, cervical lymphadenopathy, and marked fatigue. A peripheral blood smear shows atypical lymphocytes. Heterophile antibody test is positive. Which complication should be avoided during recovery?
- Swimming in chlorinated pools
- Contact sports (Correct answer)
- Eating spicy foods
- Prolonged sun exposure
Correct answer: Contact sports
Infectious mononucleosis (EBV) can cause splenomegaly, making contact sports dangerous due to risk of splenic rupture, which is the most serious complication.
Question 3: A 40-year-old immunocompromised patient presents with painful vesicular lesions along a unilateral dermatomal distribution on the chest. Which antiviral, started within 72 hours of rash onset, is the treatment of choice?
- Oseltamivir 75 mg BID × 5 days
- Acyclovir 800 mg PO 5 times daily × 7–10 days
- Valacyclovir 1000 mg PO TID × 7 days (Correct answer)
- Famciclovir 500 mg PO TID × 7 days
Correct answer: Valacyclovir 1000 mg PO TID × 7 days
Valacyclovir 1000 mg TID for 7 days is preferred over acyclovir for herpes zoster (shingles) due to better bioavailability and simpler dosing schedule.
Question 4: A 50-year-old returns from a trip to sub-Saharan Africa with fever, chills, and rigors occurring every 48 hours. Blood smear reveals ring-form trophozoites with appliqué (accolé) positioning and no Schüffner's dots. Which Plasmodium species is most likely responsible?
- Plasmodium vivax
- Plasmodium ovale
- Plasmodium falciparum (Correct answer)
- Plasmodium malariae
Correct answer: Plasmodium falciparum
Plasmodium falciparum shows ring-form trophozoites with appliqué positioning, multiple rings per RBC, and no Schüffner's dots — and is the most dangerous species causing severe malaria.
Question 5: A 68-year-old nursing home resident develops sudden onset high fever, myalgias, headache, and dry cough during influenza season. Rapid influenza test is positive. Which antiviral is most appropriate if started within 48 hours?
- Amantadine 100 mg PO BID × 5 days
- Zanamivir 10 mg inhaled BID × 5 days
- Oseltamivir 75 mg PO BID × 5 days (Correct answer)
- Baloxavir 40 mg PO single dose
Correct answer: Oseltamivir 75 mg PO BID × 5 days
Oseltamivir (Tamiflu) 75 mg PO BID for 5 days is the preferred neuraminidase inhibitor for influenza treatment in most clinical settings due to oral administration and proven efficacy.
Question 6: A 30-year-old IV drug user presents with fever, new holosystolic murmur at the right sternal border, and multiple septic pulmonary emboli on CT scan. Which organism is most commonly responsible for right-sided endocarditis in IV drug users?
- Streptococcus viridans
- Staphylococcus epidermidis
- Staphylococcus aureus (Correct answer)
- Enterococcus faecalis
Correct answer: Staphylococcus aureus
Staphylococcus aureus is the most common cause of right-sided infective endocarditis in IV drug users, typically affecting the tricuspid valve.
Question 7: A 5-year-old child presents with high fever, inspiratory stridor, drooling, and sitting in the 'tripod position.' Lateral neck X-ray shows the 'thumbprint sign.' Which organism is the most likely cause?
- Parainfluenza virus
- Staphylococcus aureus
- Haemophilus influenzae type b (Correct answer)
- Moraxella catarrhalis
Correct answer: Haemophilus influenzae type b
The 'thumbprint sign' on lateral neck X-ray indicates epiglottic enlargement caused by Haemophilus influenzae type b in unvaccinated children, a life-threatening emergency.
PANCE Infectious Disease 2
A 55-year-old diabetic patient presents with severe right ear pain, purulent otorrhea, and facial nerve palsy.
CT scan shows bony erosion at the skull base.
Which organism is responsible for this condition?