Departments of Rheumatology and
1 Neuroradiology, Dijon University Hospital, France
SIR, As the treatment of pyogenic infective spondylitis is based on appropriate antibiotic therapy, the identification of the causative micro-organism is highly desirable. Thus, the investigations performed prior to initiation of therapy must include blood and, if negative, disco-vertebral biopsy cultures [1]. Moreover, since it is thought that such biopsies can result in transient blood bacteriaemia, additional blood cultures in the minutes and hours following the biopsy are often recommended. However, to our knowledge, the usefulness of post-biopsy blood cultures has never been assessed. The aim of this work was to evaluate the diagnostic value of such blood cultures.
For this purpose, the data of every patient hospitalized in our rheumatology unit between 1991 and 2001 for pyogenic infective spondylitis were retrospectively reviewed. The diagnosis was made in the presence of clinical, laboratory and imaging (including bone scintigraphy and/or CT scan and/or magnetic resonance imaging) evidence of pyogenic infective spondylitis, and (i) the presence of micro-organism on blood culture and/or disco-vertebral biopsy, or (ii) the efficacy of empirical antibiotic treatment on clinical, laboratory and imaging parameters. Among these patients, the characteristics of those in whom a disco-vertebral biopsy was performed were reviewed.
During the evaluation period, 56 patients were hospitalized for pyogenic infective spondylitis. Among these, a percutaneous X-ray guided disco-vertebral biopsy was performed in 35 whose pre-biopsy blood cultures were negative. The characteristics of these 35 patients are shown in Table 1. Of the 35 biopsy cultures, 24 (68.6%) were positive. In all patients, three additional blood cultures were performed from 30 min to 4 h following the biopsy. These cultures were considered as positive if at least two out of three revealed the same micro-organism. Of the 35 patients, blood cultures performed after disco-vertebral biopsies were positive in 7 (20%). In one patient, for whom all other cultures, including those obtained from disco-vertebral biopsy, were negative, a positive blood culture was of great therapeutic interest, as it revealed Esherichia coli. In five other patients, the causative micro-organism had been isolated from the disco-vertebral biopsy cultures, but the positive blood culture was of therapeutic interest, in that it revealed a previously observed uncommon and/or saprophytic micro-organism (Staphylococcus epidermidis in three patients, Capnocytophaga in one, and Pyocyanic bacillus in two). Thus, the blood cultures made it possible to conclude that the micro-organism obtained on disco-vertebral biopsy was not due to contamination, and was involved in the vertebral infection.
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Conflict of interest
The authors have declared no conflicts of interest.
Notes
Correspondence to: J. F. Maillefert, Department of Rheumatology, Hôpital Général, 3 rue du Fb Raines, 21000 Dijon, France. E-mail: jean-francis.maillefert{at}chu-dijon.fr
References
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