Weighted-incidence syndromic combination antibiogram (WISCA) to guide antibiotic regimens for empiric treatment of prosthetic joint infections: A retrospective cohort study

<h2>Abstract</h2><h3>Objectives</h3> Prosthetic Joint infections (PJI) are now routinely treated with oral antibiotics, but selecting empiric regimens is challenging, including for treatment of culture negative PJIs. Although antibiograms can guide antimicrobial selection in the absence of patient-specific microbiology, a weighted-incidence syndromic combination antibiogram (WISCA) provides more useful information on likelihood of covering an infectious syndrome instead of individual pathogens and can assess multi-drug regimens. <h3>Methods</h3> A retrospective chart review of revision arthroplasties between 2016 and 2022 was used to identify those meeting the PJI case definition. For all revisions classified as PJIs, microbiologic results were used to generate a WISCA for common single and dual antibiotic regimens. <h3>Results</h3> 1722 revision arthroplasties were reviewed and 321 met the criteria for PJI among 264 unique patients. 284 of these were bacterial PJIs with 410 bacterial isolates. A WISCA demonstrated that monotherapy provided limited coverage; vancomycin, daptomycin, and linezolid were the most effective monotherapy with 80.9% (95%CI 76.3-85.4) to 82.5% (95%CI 78.1-86.9) coverage while other agents provided only 56.5% (95%CI 50.8-62.1) to 72.5% (95%CI 68.1-76.9) coverage. Dual regimens provided greater coverage; the combination of doxycycline and fluoroquinolones provided 90.3% (95%CI 87.3-93.2%) to 91.0% (95%CI 88.6-93.4%) coverage which was similar to most combination intravenous regimens. <h3>Conclusions</h3> An oral regimen consisting of doxycycline and a fluoroquinolone provides adequate coverage for PJIs and should be considered for culture negative PJIs in regions where rates of <i>Staphylococci</i> fluoroquinolone and doxycycline resistance is low. Given regional differences in resistance patterns, the protocol within this study could be used to create a local WISCA.