Filamentous Organisms in a Blood Culture

A 79-year-old male presented to our institution with a fever of 100.9^oF, shaking, chills, altered mental status, and 2 episodes of seizures. His prior medical history is significant for dementia, myasthenia gravis, type 2 diabetes mellitus, hypertension, right frontal hemorrhagic stroke, benign prostatic hyperplasia, and 2 simple kidney cysts. He was diagnosed 6 weeks earlier with an Escherichia coli bacteremia with no known source and with acute cystitis and hematuria caused by Klebsiella pneumoniae. Both organisms were pansensitive, and he was treated for 4 days with piperacillin–tazobactam and for 10 days with cefdinir. Follow-up blood cultures after 2 days showed no growth. His current urinalysis results showed negative nitrite, positive leukocyte esterase, and the presence of both red and white blood cells (WBC >50 and RBC >50/high-powered field). Blood and urine cultures were sent to the laboratory. The patient was started on empiric vancomycin and piperacillin–tazobactam but expired less than 24 hours later. The anaerobic blood culture bottle flagged positive after 98 hours of incubation, with the Gram stain showing long, gram-variable filaments containing bulbous inclusions (Figure 1).