Epidemiological characteristics and predictors of Staphylococcus aureus infection in patientswith chronic osteomyelitis of the extremities

OBJECTIVE  To analyze the epidemiological characteristics and predictive factors of Staphylococcus aureus infection in patients with chronic osteomyelitis of the extremities, and provide a reference for developing precise empirical antibiotic strategies and perioperative management plans.

METHODS  A retrospective analysis was conducted on the clinical data of 201 patients with chronic osteomyelitis of the extremities admitted to the Department of Orthopedics, Chinese PLA General Hospital, between Jan. 2021 and Jun. 2024. These patients were divided into three groups based on the etiology results: S. aureus group, other bacteria group and culture-negative group. The groups were compared regarding age, sex, body mass index （BMI）, disease duration, bone defect volume, comorbidities, and laboratory parameters. Binary logistic regression analysis was used to identify the serological predictors for S. aureus and blood culture-positive patients.

RESULTS  A total of 201 patients （mean age 45 years, 148 males） were included. A total of 194 strains of pathogenic bacteria were isolated from the cultures, including 56 strains of S. aureus （27.86%）. No statistically significant differences were found in age, gender, BMI, disease duration, hypertension, diabetes mellitus, chronic kidney disease, hepatitis, coronary heart disease, smoking history, bone defect volume, C-reactive protein and procalcitonin levels among the three groups. Regression analysis with S. aureus infection as the outcome showed: in univariate analysis, white blood cell count ≥10×10⁹/L and erythrocyte sedimentation rate （ESR） ≥20 mm/h were associated with S. aureus infection （both P＜0.05）, and after adjusting for confounding factors in multivariate analysis, white blood cell count ≥10×10⁹/L （adjusted Odds Ratio OR = 2.777, 95%CI: 1.046−7.379, P=0.040） and ESR ≥20 mm/h （adjusted OR=2.244, 95%CI: 1.166−4.319, P=0.016） remained as independent predictors. In addition, ESR ≥20 mm/h was a predictor for patients with positive cultures （adjusted OR=2.017, 95%CI: 1.046−4.164, P=0.037）.

CONCLUSIONS  S. aureus is a prevalent pathogen in patients with chronic osteomyelitis of the extremities. Elevated white blood cell count and erythrocyte sedimentation rate are independent predictors of S. aureus infection. These readily available indicators can inform rapid clinical decision-making and guide empirical antimicrobial therapy.