Vertebral osteomyelitis in patients with Staphylococcus aureus bloodstream infection: Evaluation of risk factors for treatment failure.

Objectives: Staphylococcus aureus is the most common cause of pyogenic vertebral osteomyelitis (VO). Studies indicate that S. aureus VO results in poor outcome. We aimed to investigate risk factors for treatment failure in patients with Staphylococcus aureus bloodstream infection (SAB) and VO.

Methods: We conducted a post hoc-analysis of data from a German bi-center prospective SAB cohort (2006-2014). Patients were followed-up for one year. Primary outcome was treatment failure defined as relapse and/or death within one year.

Results: A total of 1069 patients with SAB were analyzed, with 92 VO patients. In addition to antibiotic treatment, surgery was performed in 60/92 patients. Treatment failed in 44/92 patients (death, n = 42; relapse, n = 2). Multivariable analysis revealed higher age (HR 1.04 [per year], 95%CI 1.01-1.07), Charlson comorbidity index (HR 1.20, 95%CI 1.06-1.36), presence of neurologic deficits (HR 2.53, 95%CI 1.15-5.53) and local abscess formation (HR 3.35, 95%CI 1.39-8.04) as independent risk factors for treatment failure. In contrast, surgery seemed to be associated with a favourable outcome (HR 0.45 (95%CI 0.20-0.997)).

Conclusion: SAB patients with VO exhibit a high treatment failure rate. Red flags are older age, comorbidities, neurologic deficits and local abscess formation. Whether these patients benefit from intensified treatment (e.g. radical surgery, prolongation of antibiotics) should be investigated further.