One-hundred and thirty-four adult patients were treated with oritavancin for acute osteomyelitis as diagnosed by clinical assessment, baseline MRI, microbiology, and inflammatory markers between 1 January 2016 and 31 December 2018. Baseline characteristics are listed in Table 1.
Patients received infusions at 20 infusion centers in six states under the care of 37 infectious diseases specialists. The selection of oritavancin as the therapeutic agent of choice was based on patient preference or transportation challenges in 89.6% of cases.
Microbiologic analysis recovered 121 (90.3%) positive cultures from debridement of bone or joint and seven (5.2%) from curettage of wounds. Culture results were positive in 119 (88.8%) patients with several cultures confirming a polymicrobial Gram-positive infection.
MRSA was the most common pathogen isolated (92/128; 71.9%) and 80.5% (74/92) were monomicrobial. Baseline bacteremia was identified in nine (6.7%) patients; all patients had a retained indwelling intravenous catheter placed during hospitalization. Repeat blood cultures were performed in all patients with baseline bacteremia and revealed clearance of pathogens; see Table 2 for microbiology.
Clinical outcomes are shown in Table 3. Clinical outcomes were reported at the ETE timepoint for 134 patients and at the PTE for 130 patients. Clinical success was observed in 118 (88.1%) of 134 patients at ETE; all evaluable patients (excluding patients lost to follow-up) with clinical success at ETE carried forward to PTE showed a clinical success rate of 91.2% (104/114). Overall, of 130 patients evaluable at both ETE and PTE timepoints, clinical success was seen in 80.0% (104/130). Only four patients were lost to follow-up during the 6-month evaluation period. During the PTE follow-up time frame, there were nine (6.7%) patients admitted to the hospital but none for osteomyelitis, so these were not included as clinical failures. Thirteen patients (9.7%) were deemed to have a persistent or relapsing infection (nine patients at ETE and four at PTE) and thus were classified as clinical failures. In another six patients, the need for additional antibiotic therapy post-oritavancin treatment was counted as a clinical failure.
Post-treatment imaging was not routinely performed, and no additional culture data were collected; however, CRP (C-reactive protein) and ESR (erythrocyte sedimentation rate) values were decreased by at least 50% in 134 (100%) and 123 (93.2%) of patients, respectively, at ETE.
AEs were evaluated during the entire 6-month period and occurred in five patients. All AEs occurred during the oritavancin infusion upon infusion of either the second or the third dose. Three patients experienced hypoglycemia-related symptoms. Two of the five patients had tachycardia during the infusion, of whom one experienced chest pain. Oritavancin infusion was discontinued for both patients, diphenhydramine was administered, and symptoms resolved. Both patients were evaluated in the emergency room, but were not admitted to the hospital. Both patients eventually finished their course of oritavancin therapy. All patients finished treatment regimens.