Post-Radiation Microbiological Changes in Osteoradionecrosis: Investigating the Microbial Landscape

To evaluate the microbiologic characteristics, antibiotic resistance patterns, and clinical predictors of reconstruction in patients with osteoradionecrosis of the jaw (ORNJ).

Retrospective cohort study.

Single tertiary care academic medical center.

Eighty-four adult patients treated for ORNJ between January 2023 and August 2024 were included. Clinical and microbiologic data were extracted from the electronic health record. Culture results, antibiotic resistance profiles, and reconstructive outcomes were analyzed. Logistic regression was used to identify predictors of autologous reconstruction, Gram-negative infection, and Actinomyces isolation.

Among 84 patients (median age 63.3), 73.8% had cultures obtained, and 92.9% received antibiotics. Bacterial species were isolated in 58.2% of 134 cultures, with Actinomyces (23.9%) and Streptococcus anginosus (7.5%) most frequent. Gram-negative organisms were identified in 22.6% and independently predicted autologous reconstruction (odds ratio [OR] = 14.81; 95% confidence interval [CI]: 2.59-84.67; P = .0025). Fistula presence was significantly associated with Gram-negative infection (OR = 6.57; 95% CI: 1.76-24.47; P = .005). High resistance was observed to ampicillin (47.1%) and cefazolin (35.3%), while gentamicin showed the highest susceptibility (75.9%). Posterior mandibular involvement and pathologic fracture were associated with reduced odds of reconstruction.

ORNJ exhibits a polymicrobial and antibiotic-resistant profile. Gram-negative infection is a key predictor of the need for autologous reconstruction and may reflect more severe disease. These findings support the use of culture-directed therapy and highlight the importance of integrating microbiologic and anatomic factors in ORNJ management.

IV.