Pathologic Quiz Case An 18-Year-Old Man Presenting With Sepsis Following a Recent Pharyngeal Infection

An 18-year-old, previously healthy man presented to his physician with a 1-week history of fever, nausea, vomiting, diarrhea, decreased oral intake, and back and neck pain. He had been treated 6 days earlier for a ‘‘throat infection’’ with ciprofloxacin, and the throat infection seemed to have resolved. The patient appeared generally ill without localizing signs or symptoms, and was admitted to the hospital with a clinical impression of pneumonia. Complete blood count on admission showed an elevated leukocyte count of 16 900/mL (reference range 4800‐10 800/mL) with 47% band forms on the differential count, as well as toxic granulation. Chest radiograph showed evidence of bilateral pneumonia, and follow-up chest computed tomographic scan showed a nodular appearance of some of the pulmonary infiltrates, suggesting septic pulmonary emboli (Figure 1, arrow). Computed tomographic scan of the neck was also performed, which showed thrombosis of the right internal jugular vein (Figure 2, arrow). A throat swab was collected for culture, and no b-hemolytic streptococci were isolated. Two sets of blood cultures were collected 10 minutes apart, and growth was detected in both anaerobic bottles (first detection at 41.2 hours of incubation) by the BacT/ALERT (bioMerieux, Inc, Durham, NC) automated microbial detection system. Subculture plates showed anaerobic growth only, with slightly hemolytic colonies on sheep’s blood agar, which turned green after exposure to air (Figure 3). The organism was identified by the RapID ANA II System (Remel, Inc, Lenexa, Kan) in 4 hours as Fusobacterium necrophorum (with 99.8% accuracy). Gram stain from the colonies showed pleomorphic gram-negative rods with rounded ends. What is your diagnosis?