The burden of Surgical Site infections with pathogens presumably resistant to perioperative prophylaxis in orthopaedic tumour surgery: Secondary analysis of the PARITY trial

Background Surgical procedures for malignant bone tumours of the lower extremity are associated with a significant risk for surgical site infection (SSI). Little is known about the microbiology and risk factors for resistant SSIs in this population. Methods We describe the characteristics and microbiology of SSIs as well as risk factors for antimicrobial resistance against antibiotics used for perioperative prophylaxis in a secondary analysis of the PARITY trial population. The PARITY trial assessed the effect of short-term (24 hours) versus long-term (five days) postoperative antibiotic prophylaxis on the SSI incidence in orthopaedic oncology. Results SSI were identified in 96 of 604 patients (15.9%), with at least one pathogen isolated in 73 (76.0%). The most common pathogens were coagulase-negative staphylococci (34.4%), Staphylococcus aureus (24.0%), and Enterobacterales (22.9%). The proportion of pathogens with presumed resistance against cephalosporins was similar in the two groups (65.9% in the short-term vs. 71.9% in the long-term arm; OR 0.76, 95% CI 0.28, 2.06; p=0.583). Neutropenia (22.9% vs. 4.8%; OR 5.95, CI 0.72, 49.45; p=0.062) and initiation of antibiotics more than seven days before SSI diagnosis (50.0% vs. 34.8%; OR 1.88, CI 0.68, 5.21; p=0.225) were numerically but not statistically significantly more common in those with presumed resistance. Conclusions SSI due to pathogens presumably resistant to the systemic or local prophylactic agents used are common in patients undergoing reconstruction for bone tumours. Selection of presumably resistant pathogens is not driven by duration of antibiotic prophylaxis; however, antibiotic-loaded cement was associated with resistance.