# The Burden of Surgical Site Infections With Pathogens Presumably Resistant to Perioperative Prophylaxis in Orthopedic Tumor Surgery: Secondary Analysis of the Prophylactic Antibiotic Regimens in Tumor Surgery (PARITY) Trial

## TL;DR

This study finds that surgical site infections after bone tumor surgery are common and often caused by antibiotic-resistant bacteria, which are not significantly affected by the length of antibiotic use but may be linked to antibiotic-loaded cement.

## Contribution

The study identifies the prevalence and characteristics of antibiotic-resistant surgical site infections in orthopedic tumor surgery and evaluates risk factors for resistance.

## Key findings

- Surgical site infections occurred in 15.9% of patients, mainly caused by staphylococci and Enterobacterales.
- Pathogens resistant to perioperative antibiotics were common but not influenced by the duration of prophylaxis.
- Antibiotic-loaded cement was associated with resistance to prophylactic agents.

## Abstract

Surgical procedures for malignant bone tumors of the lower extremity are associated with a significant risk of surgical site infection (SSI). Little is known about the microbiology and risk factors for resistant SSIs in this population.

We describe the microbiological and other characteristics and of SSIs, as well as risk factors for antimicrobial resistance against antibiotics used for perioperative prophylaxis in a secondary analysis of the Prophylactic Antibiotic Regimens in Tumor Surgery (PARITY) trial population. The PARITY trial assessed the effects of short-term (24 hour) versus long-term (5-day) postoperative antibiotic prophylaxis on the SSI incidence in orthopedic oncology.

SSIs were identified in 96 of 604 patients (15.9%), with ≥1 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 proportions of pathogens with presumed resistance against cephalosporins were similar in the 2 groups (65.9% in the short-term vs 71.9% in the long-term arm; odds ratio [OR], 0.76 [95% confidence interval, .28–2.06]; P = .58). Neutropenia (22.9% vs 4.8%; OR, 5.95 [95% confidence interval, .72–49.45]; P = .06) and initiation of antibiotics >7 days before SSI diagnosis (50.0% vs 34.8%; OR, 1.88 [.68–5.21; P = .22) were numerically but not statistically significantly more common in those with presumed resistance.

SSIs due to pathogens presumably resistant to the systemic or local prophylactic agents used are common in patients undergoing reconstruction for bone tumors. The selection of presumably resistant pathogens is not driven by the duration of antibiotic prophylaxis; however, antibiotic-loaded cement was associated with resistance.

We identified surgical site infections in 16% of patients after bone tumor surgery, primarily due to staphylococci and Enterobacterales. Pathogens resistant to perioperative prophylaxis were frequent but not influenced by the duration of prophylaxis. Antibiotic-loaded cement was associated with resistance.