Antimicrobial drug use in horses undergoing colic surgery in Germany

A Pilot Randomised Clinical Trial Comparing a Short-Term Perioperative Prophylaxis Regimen to a Long-Term Standard Protocol in Equine Colic Surgery

Background: For surgical interventions classified as clean or clean-contaminated, including laparotomy, guidelines in human and veterinary medicine recommend a short-term perioperative antibiotic prophylaxis (PAP). In equine colic surgery, however, PAP commonly exceeds 24 h. Objectives: The aim of this study was to compare a single-shot to a 5-day lasting PAP considering surgical site infections (SSI) and other adverse effects probably associated with the particular antimicrobial regimen. Study design: The study was designed as a randomised non-inferiority pilot study including horses subjected to colic surgery while receiving one of two distinct PAP regimens. Methods: All horses (n = 67) included in the study received the standard physical examination before and after surgery. Colic surgery was performed according to the current standard of the clinic. Horses were randomly assigned to two groups, receiving either the “single-shot” or the “5-day lasting” antibiotic prophylaxis. The “single-shot” group (n = 30) received penicillin and gentamicin only once before and, if needed, during surgery, whereas the “5-day lasting” group (n = 37) received antibiotics for five days. In addition to the standard laboratory examinations, serum amyloid A and fibrinogen were determined preoperatively and during five days after surgery. SSI, postoperative colitis and haemolytic anaemia were classified as postoperative complications potentially related to antibiotic use. Results: The outcome of this preliminary non-inferiority clinical trial showed that the occurrence of postoperative adverse events (i.e., SSI, postoperative colitis and haemolytic anaemia) lacked significant differences between the study groups. Main limitations: The main limitations of this study are the limited group sizes and our inability to blind the study. Conclusions: Single-shot PAP seems to be an alternative approach considering the 5-day lasting protocol commonly used in equine abdominal surgery. However, a proper hygiene management together with a close clinical and laboratory monitoring of the equine patient is indispensable.

Frequency, Local Dynamics, and Genomic Characteristics of ESBL-Producing Escherichia coli Isolated From Specimens of Hospitalized Horses

Previous research identified veterinary clinics as hotspots with respect to accumulation and spread of multidrug resistant extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (EC). Therefore, promoting the prudent use of antibiotics to decrease selective pressure in that particular clinical environment is preferable to enhance biosecurity for animal patients and hospital staff. Accordingly, this study comparatively investigated the impact of two distinct perioperative antibiotic prophylaxis (PAP) regimens (short-term versus prolonged) on ESBL-EC carriage of horses subjected to colic surgery. While all horses received a combination of penicillin/gentamicin (P/G) as PAP, they were assigned to either the “single-shot group” (SSG) or the conventional “5-day group” (5DG). Fecal samples collected on arrival (t₀), on the 3rd (t₁) and on the 10th day after surgery (t₂) were screened for ESBL-EC. All isolates were further investigated using whole genome sequences. In total, 81 of 98 horses met the inclusion criteria for this study. ESBL-EC identified in samples available at t₀, t₁ and t₂ were 4.8% (SSG) and 9.7% (5DG), 37% (SSG) and 47.2% (5DG) as well as 55.6% (SSG) and 56.8% (5DG), respectively. Regardless of the P/G PAP regimen, horses were 9.12 times (95% CI 2.79–29.7) more likely to carry ESBL-EC at t₁ compared to t₀ (p < 0.001) and 15.64 times (95% CI 4.57–53.55) more likely to carry ESBL-EC at t₂ compared to t₀ (p < 0.001). ESBL-EC belonging to sequence type (ST) 10, ST86, ST641, and ST410 were the most prevalent lineages, with bla_CTX–M–1 (60%) being the dominant ESBL gene. A close spatio-temporal relationship between isolates sharing a particular ST was revealed by genome analysis, strongly indicating local spread. Consequently, hospitalization itself has a strong impact on ESBL-EC isolation rates in horses, possibly masking differences between distinct PAP regimens. The results of this study reveal accumulation and spread of multi-drug resistant ESBL-EC among horses subjected to colic surgery with different P/G PAP regimens, challenging the local hygiene management system and work-place safety of veterinary staff. Moreover, the predominance of particular ESBL-EC lineages in clinics providing health care for horses needs further investigation.

Retrospective Identification of Bacterial Isolates From Emergency Laparotomy Surgical Site Infections in Horses

Surgical site infection (SSI) with multiresistant bacteria is an important cause of postoperative morbidity after laparotomy in horses. The objective of this study was to identify bacteria isolates and their antibiotic resistance patterns associated with the development of wound infection in horses after laparotomy. This is a retrospective case series. 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. The study group consisted of 183 (100%) horses that recovered from anesthesia 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 perioperative and postoperative antibiotics were gentamicin and amoxicillin. Limitations include poor control over exposure factors, covariates, and potential confounders during the surgery, recovery time, or period of hospitalization; relying on others for accurate outcome assessment and recordkeeping; lack of follow-up information once animals were discharged from the hospital. 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 showed high resistance to the antibiotics used before the gastrointestinal surgery.