Scintigraphic Patterns of Indium-111 Oxine-Labeled White Blood Cell Imaging of Gram-Negative versus Gram-Positive Vertebral Osteomyelitis

Abstract

Objective: The goal of the study was to investigate whether or not gram-negative organisms that secrete antichemotactic factors cause the nonaccumulation pattern of ¹¹¹In-oxine-labeled white blood cell (¹¹¹In-WBC) scans. Materials and Methods:Staphylococcus aureus (gram-positive) (group 1) was injected into 25 rabbits and Escherichia coli (gram-negative) (group 2) into another 25 to induce infection in the lumbar vertebrae or left thigh bone (femur). Sixteen successfully infected and surviving rabbits from each group were used for imaging and analysis. Of the 16 rabbits, each group included 8 with vertebral infection and 8 with femur infection. For imaging, each rabbit was injected intravenously with 11.1 MBq (300 μCi) ¹¹¹In-WBC, and images were acquired 24 h later. Microscopic histopathology was performed after decalcification to confirm osteomyelitis. Results: The ¹¹¹In-WBC accumulation was observed in 7 (87.5%) of the 8 rabbits infected with S. aureus in the vertebrae and thigh bone. Of the rabbits infected with the gram-negative vertebrae, 1 (12.5%) showed little accumulation of ¹¹¹In-WBC. Of the 8 rabbits with gram-negative-infected femurs, 1 had high accumulation and another had low accumulation of ¹¹¹In-WBC, while the rest did not show any uptake. Osteomyelitis was confirmed by histopathology in all the successfully infected rabbits used for imaging. Conclusion: In the majority of the gram-positive-infected rabbit vertebrae there was high accumulation of ¹¹¹In-WBC. However, no accumulation of ¹¹¹In-WBC was observed in most of the vertebrae infected with gram-negative organisms, which release antichemotactic factors that prevent adequate accumulation of WBC at the infected area.

Clinical application of dual-phase F-18 sodium-fluoride bone PET/CT for diagnosing surgical site infection following orthopedic surgery

“…[ 22 ] Moreover, decreased leukocyte uptake is frequently encountered in spinal infection, especially for gram-negative vertebral infection, with the accuracy being 66% for detecting vertebral osteomyelitis. [ 27 , 28 ] Ga-67 scintigraphy has high diagnostic ability for vertebral osteomyelitis, and is known as the primary gamma camera imaging method for vertebral osteomyelitis. [ 20 , 22 ] Nevertheless, it is not an optimal radionuclide for gamma camera imaging and the relatively long interval between radiotracer injection and imaging precludes the wide use of Ga-67 scintigraphy.…”

Effect of microbiological characteristics of causative micro-organisms on patterns of labeled white blood cells uptake in osteomyelitis

“…In a preclinical study, Elgazzar et al . [12] induced osteomyelitis in the vertebral and femoral bones in rabbits. The expected increased labeled WBCs uptake was observed in 14 out of the 16 sites, including both femoral and vertebral, of Gram-positive induced osteomyelitis.…”

“…Therefore, Elgazzar et al . [12] suggested that the false-negative results in cases of Gram-negative osteomyelitis could be due to the secretion of anti-chemotactic factors by these organisms with defective chemotaxis. Gram-negative organisms, unlike Gram-positive ones, are known to be associated with defective chemotaxis as they secrete anti-chemotactic factors as reported by some studies.…”

“…The diagnosis of vertebral osteomyelitis is often delayed, and most infections become chronic which lowers the sensitivity of labeled WBC scan. [12] Another possible explanation is that infection results in very high pressure in the vertebra and therefore, labeled WBCs could not migrate to the focus of infection during the available time for imaging. Palestro and Love proposed that marrow uptake of labeled WBCs in the normal spine may be greater than in the infected bone, masking the abnormality or causing a relative photogenic region.…”

“…[14] A preliminary animal study with rabbits confirmed that Gram-negative infections in vertebral and femoral osteomyelitis are associated with low to no accumulation of labeled WBCs. [12] The aim of this study is to investigate the microbiological characteristics on labeled-WBC scan in cases of nonvertebral osteomyelitis since high-pressure theory is not a factor in such sites.…”