Microbiology and antimicrobial therapy of spinal infections.

Hematogenous vertebral osteomyelitis is almost always a monomicrobial infection affecting predominantly the older population. S. aureus is the most common micro-organism isolated. Gram-negative bacilli, however, are seen primarily in elderly males with the urinary tract as the source of infection, as well as in IVDA. In the latter group, P. aeruginosa, as well as S. aureus, are the dominant microorganisms. The offending organisms are generally isolated by needle biopsy, using a cutting needle, or by open surgical biopsy when necessary. Spinal epidural abscesses have very similar microbiology. Antimicrobial therapy is generally given parenterally in high doses, together with surgical evacuation of abscesses and debridement of necrotic tissue, when necessary. Therapy may be guided by the ESR. In VO, when the patient is doing clinically well and the ESR decreases to at least half of the pretherapy value, therapy may be stopped, but continued elevation of the ESR and the presence of abscesses may necessitate more prolonged therapy. The role of oral antimicrobial therapy is currently unclear.