Retrospective identification of bacterial isolates from emergency laparotomy surgical site infections in horses

Abstract Background Surgical site infection with multiresistant bacteria is an important cause of postoperative morbidity following laparotomy in horses. Objectives To identify bacteria isolates and their antibiotic resistance patterns associated with the development of wound infection in horses following laparotomy. Study design Retrospective case series. Methods Medical records of horses that underwent ventral midline exploratory laparotomy in a four-year period at one equine hospital were reviewed. Results of microbiologic culture and susceptibility testing are described. Results The study group consisted of 183 (100%) horses that recovered from anaesthesia after laparotomy. The prevalence of infection was 19% (24/124) after first surgery and 83% (19/23) after relaparotomy. The most common microbial isolates were bacteria of the family Enterobacteriaceae followed by Staphylococcus ssp., Enterococcus ssp., Streptococcus ssp. and Bacteroides ssp. Bacteria from the family Enterobacteriaceae showed the lowest-resistance to amphenicols, cephalosporins and quinolones groups of antibiotics . Coagulase positive Staphylococci were sensitive to amphenicols and only 33% were resistant to trimethoprim/sulfamethoxazole. The most commonly used peri- and postoperative antibiotics were gentamycin and amoxicillin. Main limitations Poor control over exposure factors, covariates and potential confounders during the surgery, recovery time or period of hospitalisation. Relay on others for accurate outcome assessment and recordkeeping. Lack of follow- up information once animals were discharged from the hospital. Conclusion Despite 5 days of antibiotic prophylaxis the rate of incisional infection is still high. The most common isolates from SSI belong to the family Enterobacteriaceae and the genus Staphylococcus, which showned high resistance to the antibitics used prior to the gastrointestinal surgery.