A 4-week-old premature infant in the neonatal intensive care unit with a central venous catheter develops fever and leukocytosis. Two separate blood cultures drawn from different sites grow Staphylococcus epidermidis at 14 hours. Which finding most strongly suggests this is a true bacteremia rather than a contaminant?
A 1-year-old child with acute lymphoblastic leukemia undergoing chemotherapy is screened for tuberculosis after a known exposure. An INF-γ release assay (IGRA) is performed, and the result is reported as “indeterminate.” The test sample itself was negative for an INF-γ response. What is the most likely explanation for this result?
A 15-year-old with a history of cystic fibrosis and airway colonization with Scedosporium apiospermum undergoes a lung transplant. Post-transplant, he develops invasive pulmonary scedosporiosis. Which of the following antifungal agents is the recommended first-line therapy for this infection?
An epidemiologist is tracking respiratory virus circulation patterns in a temperate climate. A particular virus is noted to cause annual epidemics in the late winter and early spring, and its peak activity often overlaps with or immediately follows the annual respiratory syncytial virus epidemic. Which pathogen fits this distinct seasonal pattern?
An infant with congenital toxoplasmosis is treated with pyrimethamine and sulfadiazine. The infant develops neutropenia. Leucovorin (folinic acid) is administered to counteract the bone marrow toxicity of pyrimethamine. Why is leucovorin effective in the human host but does not interfere with the drug’s anti-parasitic action on Toxoplasma gondii?
A 4-week-old infant develops a urinary tract infection with Enterococcus faecalis. Which of the following represents an intrinsic resistance mechanism characteristic of all enterococci, complicating therapy with certain antibiotic classes?
An 11-year-old child who was born and raised in the United States requires tuberculosis screening due to a household contact with active disease. The child has no history of BCG vaccination. An INF-γ release assay (IGRA) is performed instead of a tuberculin skin test (TST). What is a key advantage of IGRA over TST in this particular patient?
A term newborn is delivered to a mother who was diagnosed with a primary HIV infection at 34 weeks of gestation. Despite the immediate initiation of cART, her plasma HIV RNA level at the time of delivery is 15,000 copies/mL. Which of the following is the most appropriate antiretroviral management for this high-risk infant?
An 8-year-old boy presents with a 5-day history of fever of 40°C (104°F), a diffuse rash, and is now in shock requiring vasopressor support. He had a mild cough and runny nose about a month ago. To meet the CDC’s surveillance case definition for Multisystem Inflammatory Syndrome in Children (MIS-C), which of the following specific laboratory criteria for inflammation must be met?
A 4-year-old child with severe Plasmodium falciparum malaria develops a coma. On fundoscopic exam, retinal hemorrhages and peripheral retinal whitening are noted. What is the clinical significance of these “malaria retinopathy” findings?
