Abstract
Pyogenic spinal infection continues to represent a worldwide problem. In approximately one-third of patients with pyogenic spondylodiscitis, the infectious agent is never identified. Of the cases that lead to organismal identification, bacteria are more commonly isolated from the spine rather than fungi and parasites. This study applied universal prokaryotic 16S rRNA PCR as a rapid diagnostic tool for the detection of bacterial agents in specimens from patients suspected of pyogenic spondylodiscitis. Gram and Ziehl-Neelsen staining were used as a preliminary screening measure for microbiologic evaluation of patient samples. PCR amplification targeting 16S rRNA gene was performed on DNA extracted from 57 cases including specimens from epidural abscesses, vertebral, and disc biopsies. Positive samples were directly sequenced. MRI findings demonstrated that disc destruction and inflammation were the major imaging features of suspected pyogenic spondylodiscitis cases, as 44 cases showed such features. The most common site of infection was the lumbar spine (66.7%), followed by thoracic spine (19%), the sacroiliac joint (9.5%), and lumbar-thoracic spine (4.8%) regions. A total of 21 samples amplified the 16S rRNA-PCR product. Sanger sequencing of the PCR products identified the following bacteriological agents: Mycobacterium tuberculosis (n = 9; 42.9%), Staphylococcus aureus (n = 6; 28.5%), Mycobacterium abscessus (n = 5; 23.8%), and Mycobacterium chelonae (n = 1; 4.8%). 36 samples displayed no visible 16S rRNA PCR signal, which suggested that non-bacterial infectious agents (e.g., fungi) or non-infectious processes (e.g., inflammatory, or neoplastic) may be responsible for some of these cases. The L3–L4 site (23.8%) was the most frequent site of infection. Single disc/vertebral infection were observed in 9 patients (42.85%), while 12 patients (57.15%) had 2 infected adjacent vertebrae. Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) inflammatory markers were noted in majority of the patients. In conclusion, microbiological methods and MRI findings are vital components for the proper diagnosis of pyogenic spondylodiscitis. Our findings suggest that molecular methods such as clinical application of 16S rRNA PCR and sequencing may be useful as adjunctive diagnostic tools for pyogenic spondylodiscitis. The rapid turnaround time of 16S rRNA PCR and sequencing submission and results can potentially decrease the time to diagnosis and improve the therapeutic management and outcome of these infections. Although S. aureus and M. tuberculosis were the most common causes of pyogenic spinal infections in this study, other infectious agents and non-infectious etiologies should be considered. Based on study results, we advise that antibiotic therapy should be initiated after a definitive etiological diagnosis.
Highlights
Pyogenic spinal infection continues to be a worldwide problem
None of the patients were under non-steroidal anti-inflammatory treatment, but 4 patients had received empiric intravenous antibiotic therapy against the most common bacterial agents for spondylodiscitis
In order to expedite the rapid diagnosis of spinal infection, molecular methods have been recently applied by the use of various PCR and real time PCR techniques (Choe et al, 2014)
Summary
Pyogenic spinal infection continues to be a worldwide problem. Pyogenic spinal infection represents a rare but broad spectrum of diseases such as pyogenic spondylitis, spondylodiscitis (vertebral osteomyelitis), septic discitis, and epidural abscess. Pyogenic spondylodiscitis diagnosis is typically made on the basis of clinical symptoms, serological and hematological laboratory data, radiological findings, and employing other laboratory procedures on tissue samples including microbiological culture, histology, and molecular analyses. Clinical findings and serological laboratory data are sensitive, they lack diagnostic specificity for pyogenic spondylodiscitis. Radiological findings, especially magnetic resonance imaging (MRI), may show specific changes in some pyogenic spondylodiscitis cases, but provide no information about the etiological agent (Sobottke et al, 2008; Zimmerli, 2010). Since the spectrum of etiologic agents is diverse, the definitive diagnosis of the causative agent is through microbiologic culture or other rapid identification tests. Microbiological diagnosis may fail due to antibiotic treatment before tissue sampling or difficulty in culturing the causative agent (Chelsom and Solberg, 1998; Butler et al, 2006). Inappropriate antibiotic use can result in prolonged hospital stays and increased costs, but it can have adverse consequences on the patient’s prognosis
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