Oral versus standard antimicrobial treatment for pyogenic native vertebral osteomyelitis: a single center, retrospective, propensity score balanced analysis.

Abstract Background Interest toward shorter antimicrobial regimens and oral treatment for osteoarticular infections is growing. The aim of this study is to assess whether there is an association between the administration of an entirely oral antibiotic therapy (OT) and the clinical outcome of native vertebral osteomyelitis (NVOs). Methods Single center, retrospective, observational study on consecutive patients with pyogenic NVOs over a 10-year period (2008-2018). Multivariate logistic regression analysis was carried out to identify risk factors for clinical failure, both in the whole population and in subgroups. The impact of OT versus standard treatment (intravenous induction followed by oral treatment whenever possible) was assessed in patients with a non-multidrug resistant microorganism (MDRO) etiology and the impact of a rifampin-containing regimen was assessed in patients affected by NVOs caused by staphylococci or of unknown etiology. Results Study population included 249 patients, 33 (13.3%) experienced clinical failure; OT group consisted of 54 patients (21.7%). Multivariate regression analysis of the whole population selected Charlson Comorbidity Index (aOR 1.291, 95% CI 1.114-1.497, p = 0.001) and MDRO etiology (aOR 3.301, 95% CI 1.368-7.964, p = 0.008) as independent factors for clinical failure. Among patients affected by a non-MDRO NVO, OT was not associated with an increased risk of clinical failure (aOR 0.487, 95% CI 0.133-1.782, p value = 0.271), even after adjustment for the propensity score of receiving OT. In the subgroup of patients with staphylococcal or unknown etiology NVO rifampin was independently associated with favorable outcome (aOR 0.315, 95% CI 0.105-0.949, p value = 0.040) Conclusions An entirely oral, highly bioavailable treatment, including rifampin, may be as effective as parenteral treatment in selected patients with NVOs.