A case of Staphylococcus epidermidis osteomyelitis in the absence of spine hardware

Abstract

Staphylococcus epidermidis is a typically indolent pathogen that is often considered a blood culture contaminant. It is a rare and unexpected cause of osteomyelitis, especially in the absence of recent surgical intervention or orthopedic implants. We highlight a case in which a 90-year-old Caucasian male with no recent spine surgery was found to have osteomyelitis of the lumbar spine and repeat positive blood cultures for methicillin resistant Staphylococcus epidermidis (MRSE). Further investigation revealed a history of mitral valve replacement and a new diagnosis of endocarditis leading to persistent bacteremia and seeding of his lumbar vertebrae. This case demonstrates that S. epidermidis can cause vertebral osteomyelitis resulting in severe complications that are more similar to highly pathogenic bacteria. We describe the steps to diagnosing this chronic undetected infection and related comorbidities.

Keywords: Endocarditis; Magnetic Resonance Imaging (MRI); Osteomyelitis; Staphylococcus epidermidis.

Fig. 1

Discitis-osteomyelitis changes on CT. Comparing to prior CT L-spine from March 2022 (A), a CT L-spine from August 2022 (B) shows new prominent erosive endplate changes at L1-L2 (arrows) and some erosion at L3-L4, concerning for discitis-osteomyelitis.

Fig. 2

MRI confirms discitis-osteomyelitis changes observed on CT. Sagittal STIR (A) and post-contrast images (B) demonstrate prominent edema and enhancement of the L1 and L2 vertebral bodies and within the L1-L2 intervertebral disc, compatible with discitis-osteomyelitis. There is also mild edema and enhancement of the L3-L4 vertebral endplates, which in conjunction with new erosive endplate changes seen on the CT, are suggestive of early discitis-osteomyelitis at this level. C. Axial STIR image demonstrates a small heterogeneous collection in the right psoas muscle. D. There is no definite rim-enhancement on the Axial T1 post-contrast image. Therefore, this is most compatible with a phlegmon, rather than a frank abscess. Axial T1 post-contrast image also demonstrates diffuse enhancement of the bilateral psoas muscles compatible with inflammatory change.