Does colonization with MRSA, ESBL - producing Enterobacteriaceae, and/or Acinetobacter baumannii - increase the risk for postoperative surgical site infection?

Objective: Evaluation of the role of indicator pathogens in equine surgical site infection (SSI) and other infection-promoting factors.

Study Design: Cross-sectional study.

Animals: Horses presenting with an open injury or surgical colic during 1.5 years.

Methods: A nasal swab and a faecal sample were collected from every patient upon admission. Furthermore, a wound swab was collected from wounds of injured horses. Details on the wounds and procedures were documented. Laparotomy incisions and injuries were monitored for signs suggesting infection.

Results: In total, 156 horses presented because of a surgical colic (n = 48) or open injuries (n = 108). Thirteen surgical colic patients and three injured horses did not survive beyond 24 h, and four injured horses were discharged from the clinic at the day of admission. SSIs occurred in 31 (30.7%) injured horses and 11 (31.4%) horses after laparotomy. Regarding injuries, general anaesthesia increased the risk of developing a WI compared to sedation. Indicator pathogens were cultured from 29/42 SSI. In total, 10/11 infected laparotomy incisions and 19/31 injuries with SSI tested positive for multidrug-resistant pathogens (MDRPs) . Indicator pathogens were not detected at admission in any of the horses that developed incisional SSIs after laparotomy but were detected in two of the injured horses that developed SSIs.

Conclusion: MDRPs were identified in almost 70% of the SSI. Less than 5% of the affected animals were colonized with the same pathogen before admission, indicating that colonization with MDR pathogens is only one of the crucial factors for the development of SSI.

Clinical Significance: Colonization with MDRP seems not to predispose horses to MDR SSIs.