Correlation of virulence factors of S. aureus with clinical outcome in patients with S. aureus associated implant infections in orthopaedic trauma surgery in Giessen

The intention of this multidisciplinary work is to identify the pathogenicity potential of S. aureus isolated from patients with implant associated infection (IAI) and to correlate the results with clinical outcome data. This will help to identify specific virulence factors in order to improve the clinical treatment and outcome for these patients in the future. Infected implants will be aseptically removed from patients during revision surgery, sonicated and isolated bacteria will be further identified by MALDI-TOF and by specific PCRs to detect the S. aureus specific virulence genes. Patients are followed prospectively for 12 months and quality of life parameters and adverse events such as reinfections and reoperations are documented. PCR is used to identify the main pathogenic determinants including specific surface components well as the host cell tissue and encountered in biofilm formation machinery. Strains will be further phenotypically characterized through measuring its antibiotic sensitivity, hemolytic activity and its biofilm formation capabilities. Virulence of strains will be further documented by using them in in vitro infection model of osteoblast-like cell lines. The ability of the strains to invade and proliferate inside osteoblasts will be assessed. For in vivo infection experiments, the insect Galleria mellonella wax moth model will be used. These experimental data will be correlated with prospective clinical patient outcome data after 12 months which will allow to compare virulence potential of the pathogen to the clinical result in patients. The clinical impact of this work is that it will identify specific virulence factors that account for bad clinical outcome in patients for whom a more aggressive surgical treatment will be necessary in the future.