Virulence Factors and Antibiotic Susceptibility in Staphylococcus aureus Isolated from Burn Infections

Background: Burn injuries constitute a significant public health concern. A burn compromises the skin's protective barrier, resulting in the downregulation of local and systemic immunological responses. Staphylococcus aureus is among the most prevalent causes of burn wound infections. We conducted this study to detect the virulence genes, antibiotic susceptibility, and biofilm production of locally isolated S. aureus from burn infections. Methods and Results: We obtained 120 swabs from burn patients at several hospitals in Baghdad between December 2023 and March 2024. The S. aureus isolates were identified using biochemical assays and the VITEK-2 system. The Kirby Bauer test was used for antimicrobial susceptibility, and the result was evaluated based on the guidelines of CLSI 2023. The microtiter-plate assay was conducted to measure the biofilm formation at OD570 using an ELISA reader. (11) The icaA, icaD, ebpS, fnbB, and fib genes were detected by PCR. Fifty-four (45.8%) of S. aureus isolates were identified from 120 swabs of burn infections. The results demonstrated that all isolates (100%) were resistant to penicillin, 75.9% were resistant to erythromycin, 63% to tetracycline, 61.1% to oxacillin, 48.2% to imipenem, 42.6% to gentamicin, 27.8% to ciprofloxacin, 26% to vancomycin, and 9.2% to rifampicin. The rate of multidrug resistance in S. aureus isolates was 48%. The results indicated that 48.2%, 33.3%, and 18.5% of the isolates produced high, intermediate, and low biofilms, respectively. The biofilm‑related genes icaA, icaD, ebpS, fnbB, and fib were detected in 87%, 77.7%, 42.5%, 33.3%, and 51.8% of the isolates, respectively. Conclusion: Our study indicated that biofilm formation is correlated with antibiotic resistance and genes related to biofilm development. It is important to address genetic variables that affect resistance mechanisms and microbial behavior to reduce the spread of resistant strains and enhance treatment results.