Clinical Outcomes of Antipseudomonal vs. Non-Antipseudomonal Therapy in Patients with Osteomyelitis

Abstract Background Osteomyelitis (OM) in diabetics is frequently a polymicrobial infection that rarely involves Pseudomonas (4–5% of cases). Bone cultures have a low-positive yield of 34–50% and, as a result, many patients receive antimicrobial regimens which include antipseudomonal (AP) therapy. Methods A retrospective cohort analysis of adult Veterans with OM treated with AP compared with non-antipseudomonal (NAP) therapy was conducted. Patients managed by the VA St. Louis outpatient parenteral antimicrobial therapy (OPAT) service from 1/1/2009 to 7/31/2015 were identified and screened for inclusion. Patients with culture negative (CN) or non-pseudomonal superficial swab cultures (SCx) were included. Figure 1 presents the study profile and exclusion criteria. The primary outcome was clinical failure, defined as a composite of: (1) extension of antibiotics beyond 1 week of the planned duration, (2) recurrence of OM at the same anatomical site within 12 months, or (3) any unplanned surgery or amputation at the anatomical site within 12 months of ABx completion. Results Overall, 104 patients with 109 OM encounters were included; there were 29 CN encounters and 80 SCx encounters. Table 1 presents baseline demographics. The overall failure rate was 55/109 (50.5%). The results of the analysis are shown in Table 2. While not included in the primary analysis, Pseudomonas was isolated from 8/88 (9.1%) swab cultures and 5/33 (15%) deep cultures. Conclusion Empiric AP therapy did not improve clinical outcomes in patients with either CN or SCx OM. Table 1: Demographics AP (n = 43) NAP (n = 66) P-value Age, years (mean ± SD) 62 (±8.60) 62 (±9.60) 0.93 Male 42 64 1.00 White 34 55 0.57 Creatinine clearance, ml/minute (mean ± SD) 65.2 (±27.7) 62.8 (±27.4) 0.65 History of OM 6 14 0.34 Diabetes (DM) 40 55 0.14 Peripheral vascular disease (PVD) 12 26 0.22 Table 2: Analysis Clinical Cure (n = 54) Clinical Failure (n = 55) P-value DM 46 49 0.54 PVD 20 18 0.64 History of OM 12 8 0.30 MRSA therapy 33 35 0.77 AP therapy 19 24 0.37 Surgical intervention 30 21 0.07 Clostridium difficile infection 4 4 0.97 MRSA on SCx 8 / 39 7 / 41 0.69 Infection Site Lower extremity 46 53 Upper extremity 3 1 0.52 Other 5 1 Planned Duration ≥ 6 weeks 51 52 0.98 Microbiology CN 15 14 Monomicrobial 13 9 0.40 Polymicrobial 26 32 Figure 1. Trial profile. Disclosures All authors: No reported disclosures.