(897) Utility of Intraoperative Cultures in Guiding Antibiotic Therapy for Malignant Otitis Externa

Introduction: Malignant otitis externa (MOE) is a severe infection of the external auditory canal that can extend to the skull base and temporal bone, and standard treatment consists of prolonged courses of parenteral antibiotics commonly targeting Pseudomonas. In cases of severe or refractory disease, surgical debridement may be necessary, and intraoperative cultures are obtained to guide antimicrobial therapy. This study aims to evaluate whether growth from intraoperative cultures results in changes to antibiotic management.

Methods: A retrospective review was conducted of patients treated for MOE at a single tertiary care institution between March 2005 and October 2024. Collected data included demographics, inflammatory markers (A1c, WBC, ANC, ESR, CRP), preoperative and intraoperative culture results, and antibiotic regimens. Analyses were primarily descriptive.

Results: 58 patients (71% Male, 67% White) with MOE were included. Diabetes was present in 86% (50/58) and hypertension in 76% (44/58). 28 patients (48%) underwent surgery with intra-operative culture obtained. 50% (14/28) of patients had a subsequent change in antibiotics as a result of intraoperative cultures. Among the 14 patients with a change in antibiotic regimen, treatment was successful in 71% (10/14), unknown in 14% (2/14), and required readmission in 14% (2/14). Among patients managed non-operatively, 83% (25/30) were treated successfully, 13% (4/30) required readmission, and 3% (1/30) had unknown outcomes. Additionally, 22/58 patients had both pre-operative and intraoperative cultures taken, and 64% (14/22) demonstrated discordant results.

Conclusions: In select patients with severe or refractory MOE, intraoperative cultures obtained during surgical debridement may be beneficial in guiding antibiotic management and optimizing treatment success.