Intra- and Post-Operative Bacteriological Surveys of Surgical Site in Horses: A Single-Centre Study

Bacterial contamination of the surgical site in horses is a major risk factor for the development of surgical site infections (SSIs), which increase morbidity, mortality, the hospitalisation period, antibiotic use, and management costs. While contamination is a prerequisite for infection, its progression to clinical infection depends on additional factors that compromise host defences. The present study, conducted at the Veterinary Teaching Hospital of the University of Perugia over an 11-month period, investigated bacterial contamination in 70 surgeries (53 clean and 17 clean-contaminated) at the end of the procedure. To exclude pre-existing contamination, a sterile swab was collected after surgical scrub, and only cases that entered surgery with a sterile operative field were considered. A swab, biopsy, and fine-needle aspiration from the wound margins were then performed at the end of the surgery to conduct a qualitative assessment of the bacterial contamination of the surgical sites. Risk factors for surgical field contamination were analysed separately for clean and clean-contaminated procedures. Specifically, for clean-contaminated surgeries, the presence of emergency conditions, surgery duration, and intra-operative complications were evaluated. For clean surgeries, risk factors included the type of operating room, surgical duration, tissue involved, use of local anaesthetics, and placement of surgical drapes. The results revealed bacterial contamination rates of 49.1% in clean surgeries and 41.2% in clean-contaminated surgeries. Coagulase-negative staphylococci were the most frequently isolated bacteria, followed by Burkholderia cepacia, Bacillus sp., and Stenotrophomonas maltophilia. A statistical analysis showed no significant results on the predictive factors of the contamination evaluated. However, the observed trends suggest the importance of further investigating these risk factors in a larger sample size. These results emphasise the importance of effective prophylactic measures to limit surgical site contamination. Future research will focus on optimising pre-operative and intra-operative prophylaxis strategies to reduce bacterial contamination to sub-pathogenic levels, thereby enhancing post-operative outcomes.