Longitudinal study of antimicrobial-resistant commensal Escherichia coli in the faeces of horses in an equine hospital.

The research article covers a thorough study on the prevalence and risk factors of antimicrobial-resistant Escherichia coli in the feces of horses in an equine hospital. The study records an alarming rise in resistance over the stay period and identifies potential risk factors for such resistance.

Study Design and Population

• The researchers conducted a longitudinal cohort study, a design best suited for observing development, change, and outcomes over time.
• The study population consisted of 103 horses admitted to a referral equine hospital for more than 48 hours. Hence, the study did not include horses undergoing radioactive gamma scintigraphic examination, un-weaned foals, and mares with un-weaned foals.
• In order to understand the nature of antimicrobial resistance in the selected population, the team collected fecal samples from the horses upon admission and then every two days until their discharge.
• Additional information such as the horses’ treatment history and hospitalization details were also recorded to aid in the analysis.

Findings of the Study

• Fecal samples were cultured, and the antimicrobial resistance profile of the isolated E.coli strains were determined.
• The resistance to all examined antimicrobials except co-amoxiclav was alarmingly prevalent in the samples.
• The researchers noted a pattern: the resistance prevalence was lowest upon admission, but it escalated, peaking four days post-admission.

Analysis of Risk Factors

• The risk factors contributing to this rise in antimicrobial resistance were scrutinized using advanced multilevel, multivariable modeling.
• The study recorded significant “clustering” of resistance outcomes within individual horses.
• For everything except resistance to trimethoprim, the day the sample was obtained stood out as a significant risk factor – there was a marked increase in resistance for samples taken on Day 2 or later.
• The researchers also tied an increased risk of resistance to horses that had received antimicrobial treatment in the seven days prior to sampling and those that had been prescribed higher daily doses of cotrimoxazole in the preceding 24-48 hours.
• The location within the hospital and the reason for admission also emerged as significant risk factors for some of the resistance outcomes.

Implications of the Findings

• In terms of implications, the study found high levels of multidrug-resistant E. coli (affecting 47.7% of samples) and extended-spectrum β-lactamase-producing E. coli (in 27.3% of samples).
• These strains could severely complicate treatment regimes if they were the cause of infection, and might also pose significant risks to staff members who are in close contact with the horses.