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Spontaneous infectious spondylodiscitis (SIS) is an uncommon cause of low back pain in adults1 being most commonly described in children. Most cases in adults follow spinal treatment, and adult cases unrelated to previous spinal surgical procedures are considerably less common. In contrast with postoperative patients, in whom the most common infecting organisms isolated were Staphylococcus aureus and Staphylococcus epidermidis, a wide variety of infectious agents have been implicated in SIS, including Klebsiella species.1–5Klebsiella oxytoca is a non-motile, Gram negative bacillus, that can be differentiated from Klebsiella pneumoniae by its inability to produce indole from tryptophan.6 As far as we know, this is the first case of SIS caused by K oxytoca to be reported.
A 51 year old man with an antecedent of intravenous heroin addiction and two months' history of progressive thoracolumbar pain without fever was referred for investigation. Physical examination showed mild tenderness to palpation over D12-L1 and a painful paravertebral musculature contraction that limited movements of the back. Motor examination and deep tendon reflexes were normal. Several skin ulcers and venepuncture lesions in arms, hands, and legs were seen. The remainder of the examination was otherwise unremarkable.
Laboratory findings showed an erythrocyte sedimentation rate of 62 mm/1st h; C reactive protein 83 mg/l, fibrinogen 7.6 g/l, and a white blood cell count of 11.6×109/l with 78% polymorphonucleocytes. A chest radiograph and the remainder of the routine blood and urine determinations were normal. A Mantoux intradermor reaction test (2 UI PPD-RT23) was positive (15 mm in diameter). Serological tests for Brucella and HIV infection were negative and repeat sputum, blood, and urine cultures for bacteria and mycobacterium were also negative. Likewise, a skin ulcer specimen was examined and polymicrobial flora were isolated. A roentgenographic study of the lumbar spine showed degenerative changes and osteoporotic vertebral fractures in D12 and L1, and narrowing of the disc space at D12-L1. Magnetic resonance imaging (MRI) confirmed narrowing of the disc space at D12-L1, with end plate destruction of D12 and L1 (fig 1). Finally, a fine needle biopsy of the disc guided by computed tomography was performed and the specimen culture was positive for K oxytoca. In accordance with the antibiogram results, the patient received intramuscular ceftriaxone (2 g/day for six weeks). Two months later the patient had completely recovered and MRI showed significant improvement of the vertebral lesion.
Klebsiella species are an important cause of nosocomial and community acquired infection. Most of the Klebsiella strains implicated in invasive infections are K pneumoniae and <13% of episodes of bacteraemia by Klebsiella were due to K oxytoca.7–9 This micro-organism has been associated with urinary, respiratory, biliary tract, skin, and intravascular device infections.10 Although unusual, some cases of spondylodiscitiscaused by K pneumoniae have been reported.1–5 However, as far as we know this is the first reported case of SIS due to K oxytoca.
The clinical presentation of this patient was similar to that reported in other cases of SIS, irrespective of the causative organism.1 Schoferman et al pointed out that the infectious agents which play a part in SIS may be of relatively low virulence,11 causing an insidious onset and a subacute clinical course. This is in contrast with primary vertebral osteomyelitis, in which patients present a more acute course with obvious infection. In our case, blood cultures were negative. Honan et al found that 10/16 patients with spontaneous discitis also had negative blood cultures,1 underlining this possibly low virulence, although it might also be explained by the fact that discitis is delayed with respect to the bacteraemia. Likewise, it is remarkable that in the series of Lin et al, pyogenic metastatic foci were not found in any of the 43 patients with K oxytoca bacteraemia.10 These issues suggest that K oxytoca may also have only a small ability to cause septic emboli and perhaps for this reason septic complications due to K oxytoca (such as SIS) are unusual.
Lin et al found that the most common underlying diseases associated with K oxytoca bacteraemia were hepatobiliary diseases, neoplastic diseases, and diabetes mellitus.10 Other predisposing factors were prior antimicrobial treatment, urinary catheterisation or manipulation, corticosteroid treatment, recent surgery, and respiratory assistance. In our patient, none of these situations were present. He had only an active intravenous heroin addiction, and was negative for HIV infection when the spondylodiscitis developed. Many authors have concluded that immunological dysfunction has a relatively minor role in the pathogenesis of infection in injection drug users, compared with the repeated parenteral introduction of non-sterile material.12 Nevertheless, some immunological disorders have been reported, such as a depression of the blastogenic response of peripheral blood mononuclear cells to pokeweed mitogen and a depression of phagocytosis, superoxide production, and bactericidal activity of polymorphonuclear cells from intravenous heroin users.13 In these patients, osteomyelitis infection is usually due to S aureus and P aeruginosa, and the skin and the oral cavity are the most common point of entry. K oxytoca is an unusual micro-organism present in the skin, dregs being its principal source. Contamination by objects used for intravenous heroin introduction may be a possible cause of the K oxytoca infection in this case. Likewise, skin ulcers are extremely common in intravenous drug users. Although S aureus and β-haemolytic streptococci remain the most common isolates, other Gram negative bacilli such as Klebsiella have an important role. Our patient had skin ulcers and these may be other possible points of entry for K oxytoca, but in our case this micro-organism could not be isolated.
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