10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
Discharge planning is underway for an 8-year-old receiving cefazolin for acute hematogenous tibial osteomyelitis. The admission blood culture grew methicillin-susceptible Staphylococcus aureus; cultures obtained the following day were negative. MRI showed no drainable abscess or joint involvement. After five treatment days, the child has been afebrile for 72 hours and is walking with minimal discomfort. C-reactive protein has fallen from 120 to 18 mg/L. Oral intake is normal, and the family can reliably administer medication and attend follow-up. Which completion strategy best balances cure with treatment-related harm?
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Correct answer: C - Change to oral cephalexin now and complete four weeks of total antibiotic therapy, with clinical follow-up.
Question 2
A term newborn has a normal examination at 36 hours of age. The mother received stage-appropriate benzathine penicillin G for primary syphilis 16 days before delivery. At delivery, maternal serum RPR was 1:8 and infant serum RPR was 1:2, measured by the same laboratory. The infant has normal blood counts and long-bone radiographs. A traumatic lumbar puncture produces a blood-contaminated specimen that cannot be interpreted. Follow-up is reliable. Select the appropriate treatment for the infant.
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Correct answer: A - Aqueous crystalline penicillin G intravenously for 10 days
Question 3
The vancomycin monitoring results for a 10-year-old with MRSA bacteremia are:
Broth-microdilution vancomycin MIC: 1 mg/L
Bayesian-estimated AUC over 24 hours: 520 mg·h/L
Correctly timed trough concentration: 9.2 mg/L
The deep soft-tissue abscess has been drained, blood cultures have cleared, and the child is improving. Serum creatinine is unchanged. What adjustment, if any, is indicated?
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Correct answer: D - Maintain the current dose and continue monitoring vancomycin exposure and renal function.
Question 4
Six weeks after recovering from a second episode of invasive meningococcal disease, a healthy 15-year-old undergoes immune evaluation. The episodes occurred two years apart and involved different serogroups. Quantitative immunoglobulins are normal. On two properly handled fresh specimens, both CH50 and AH50 activity are undetectable, while C3 and C4 concentrations are normal. The adolescent has never received a complement inhibitor. Which defect best fits this pattern?
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Correct answer: B - Deficiency of a terminal complement component, C5 through C9
Question 5
In late June, a 6-year-old in North Carolina develops fever, severe headache, and vomiting after a camping trip. On illness day four, a nonpruritic rash appears on the wrists and ankles and spreads toward the trunk. Platelets are 84,000/µL and sodium is 128 mmol/L. No tick bite was recalled, and an acute Rickettsia rickettsii IgG assay is negative. There is no drug allergy. Which antimicrobial should be administered without waiting for convalescent testing?
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Correct answer: B - Doxycycline
Question 6
At a follow-up visit, a 17-year-old treated for uncomplicated chlamydial cervicitis learns that a Chlamydia trachomatis NAAT obtained 10 days after completing treatment is still positive. The adolescent is not pregnant, took every dose of doxycycline 100 mg twice daily for seven days, and has no residual symptoms. The partner was treated, and there has been no sexual contact since diagnosis. How should the positive result be handled?
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Correct answer: D - Give no additional antibiotic now; arrange retesting for reinfection approximately three months after treatment.
Question 7
Ultrasound in an 8-year-old with bacterial pneumonia shows a large, septated pleural collection. A small-bore chest tube is correctly positioned and drains purulent fluid, but substantial loculated fluid remains. There is no bronchopleural fistula or bleeding contraindication, and the team has selected chest-tube drainage with intrapleural treatment as the initial approach. Which intrapleural regimen is favored by the 2026 IDSA/PIDS recommendations?
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Correct answer: A - Alteplase alone
Question 8
Two independently collected shunt-reservoir CSF specimens from a 9-year-old grow penicillin-susceptible Cutibacterium acnes after six and seven days of incubation. The child has a ventriculoperitoneal shunt and three weeks of intermittent headache and vomiting. Imaging shows an abdominal pseudocyst around the distal catheter. There is no fever, and CSF cell count, glucose, and protein are within the laboratory reference ranges. What should the definitive plan include?
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Correct answer: C - Remove the shunt, establish external ventricular drainage, and administer intravenous penicillin G.
Question 9
In a randomized trial, 300 infants receive a preventive monoclonal antibody and 300 receive placebo. All infants complete follow-up through the same RSV season. RSV-related hospitalization occurs in 12 antibody recipients and 30 placebo recipients. The trial does not report outpatient infections or hospitalizations from other causes. Which absolute-benefit statement is supported for infants similar to those enrolled?
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Correct answer: D - Treating about 17 infants rather than giving placebo would prevent one additional RSV hospitalization during one season, on average.
Question 10
A newly diagnosed 3-year-old with HIV is starting antiretroviral therapy. The child has no cough, tachypnea, or hypoxemia and no medication allergy. The absolute CD4 count is 360 cells/µL, but the CD4 percentage is 26%. How do these results affect prevention of Pneumocystis pneumonia?
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Correct answer: B - Start prophylaxis with trimethoprim-sulfamethoxazole as antiretroviral therapy begins.
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