SAFELY STEPPING DOWN: OPTIMIZING THE TRANSITION TO ORAL ANTIMICROBIAL THERAPY IN BONE AND PROSTHETIC JOINT INFECTION USING A LARGE MICROBIOLOGICAL DATASET

Aim Following sterile-site sampling and excision for bone and prosthetic joint infection (B/PJI), many patients may require prolonged inpatient parenteral antibiotics whilst awaiting culture results. We investigated the impact of time to a microbiological result on the ability to safely transition to a suitable oral empiric regimen to allow accelerated discharge. Methods A retrospective review of microbiology records identified 818 patients who had sterile site sampling for B/PJI between 2022 and 2024. Of these, 558 cases were identified who had at least three sterile site samples taken at surgery and clinically significant microbiological isolates identified on culture. Key variables included time to first detection of growth (“work in progress”), time to organism identification, and time to final report. Antibiotic susceptibilities were analysed for isolates first cultured beyond 72 hours. Results In 504 of 558 cases (90.3%), all organisms flagged as work in progress within 72 hours. In 8 cases (1.4%), all organisms flagged after 72 hours, and in 46 cases (8.2%), organisms flagged as work in progress both before and after the 72-hour threshold. The most common isolates before 72 hours were Enterobacteriaceae (28.4%), Staphylococcus aureus (21.9%) Coagulase negative Staphylococcus (13.4%). After 72 hours it was Coagulase negative Staphylococcus (27.5%) and Cutibacterium acnes (27.5%). Of the Isolates flagged beyond 72 hours, 22.3% showed resistance to Clindamycin, 13.6% to Flucloxacillin, 4.5% to Doxycycline, 4.5% to Ciprofloxacin and Rifampicin and 0% to Linezolid. Conclusions Whilst it is important to undertake extended cultures for B/PJI, most patients will have indication of a pending positive culture within 72 hours. The number of cases without growth by 72 hours was low and they were typically slower-growing organisms with reasonable oral empiric options available. Early transition in this group may be safe and could reduce hospital stay, lower costs, and accelerate discharge.