Bacteriological features of implant-related infection after fracture operation and methods to identify pathogenic bacteria

Background: This study summarizes the clinical features of bacterial cultures collected from infection after fracture fixation (IAFF), compares the results of bacterial culture from debridement versus sinus tract samples, and examines the relationship between the number of culture samples and success in identifying pathogenic bacteria. Methods: A retrospective analysis of 255 patients (202 males and 53 females) with IAFF from August 2017 to April 2020 was done. Common infection sites were femur, tibiofibular, hip joint, ankle, and humerus. Debridement was performed 438 times. Samples collected during debridement were sent for bacterial culture 295 times, with a variable number of culture samples taken. All samples were sent for general bacterial culture; results were summarized and success identifying pathogenic bacteria was compared for different culture sample sizes. Results from sinus tract samples (n=57) were also compared with pathogenic bacteria found in debridement samples. Results: In patients with IAFF, debridement samples had more gram-positive than gram-negative bacteria; the top 5 bacteria presented were: Staphylococcus aureus , Staphylococcus epidermis , Pseudomonas aeruginosa , Enterobacter cloacae , and Escherichia coli. Bacteria were found in 75.6% of culture samples from debridement. Five samples showed the highest rate of detection (90.6%) and 82.8% were identified with pathogenic bacteria. The cultural results from the sinus tract matched with those from the debridement samples 67.30% of the time, while 42.10% matched the pathogenic bacteria. Conclusions: For bacterial culture, 5 or more samples can improve the pathogen detection rate. Bacterial culture of sinus tract samples is not recommended as the basis for choosing appropriate antibiotics.