1. Presented by Katelynn Davis, MD and reviewed by Sean Zhang, MD, PhD

A middle aged patient status post kidney transplant presented with progressively worsening low back pain for the last few months that was constant and worsened with activity and movement. A spinal x-ray, lumbar spine MRI, and lumbar spine CT (Figure 1) were significant for lumbosacral spine erosive endplate changes with adjacent bony sclerosis and fat stranding consistent with lumbosacral discitis and osteomyelitis. A CT-guided biopsy was performed and reported bone with mild fibrosis and reactive changes. Bacterial and fungal cultures from the biopsy site were negative. The patient continued to have worsening symptoms, so a repeat biopsy was performed. Tissue cultures were positive for an organism with the plate and microscopic images below (Figures 2, 3). Since transplantation a year ago, the patient has had repeatedly elevated beta-D-glucan tests. Around the time of the transplant, the beta-D-glucan (serum) was >500 pg/mL, and it remained elevated (90 pg/mL at the time of repeat biopsy). Galactomannan (serum) and multiple bacterial/yeast blood cultures during this course were negative.

Figure 1 - Lumbar spine CT without contrast





Figure 2 - Plate culture



Figure 3 - Microscopic - Phenol cotton blue stain



Question: The morphology shown in the culture and microscopic images above is consistent with which of the following?