In vitro antimicrobial susceptibility of equine clinical isolates from France, 2006-2016.

The research article presents a large-scale analysis of the evolution of antimicrobial susceptibility in equine pathogens isolated from clinical samples over 11 years. It highlights the frequency of multi-drug resistant strains and emphasizes the importance of responsible use of antibiotics in veterinary medicine.

Objective and Methodology

• The main aim of this research was to study the antimicrobial susceptibility evolution in various pathogens affecting horses, isolated from clinical samples over a period of 11 years (from 2006 to 2016).
• The study analyzed a large collection of 25,813 bacterial isolates. These isolates were grouped according to their origin: respiratory tract, cutaneous (skin), genital, and others.
• The antimicrobial susceptibility of these isolates was then examined using the disk diffusion method, a technique used to assess the effectiveness of antibiotics against bacteria.

Main Findings

• The most common pathogens isolated were group C Streptococci (27.6%), Escherichia coli (20.0%), Staphylococcus aureus (7.8%), Pseudomonas aeruginosa (4.0%), Enterobacter spp. (3.4%), Klebsiella pneumoniae (2.4%), and Rhodococcus equi (1.8%).
• Respiratory samples yielded the highest number of isolates—9512, or 36.8% of the total. These were followed by genital samples (29.8%) and skin samples (15.8%).
• The frequency of multi-drug resistant (MDR) strains fluctuated over the study period. Particularly, it ranged between 6.4-20.4% for group C Streptococci and 17.0-37.7% for Klebsiella pneumoniae.
• For Staphylococcus aureus, between 2006 and 2009, 24.5-43.0% were MDR; after 2009, the percentage did not exceeded 27.6%.
• Escherichia coli and Enterobacter spp. exhibited MDR levels of more than 30.0% until 2012, after which there was a significant decrease, with levels ranging between 22.5-26.3%.

Significance of the Study

• This study is significant as it represents the first large-scale analysis of its kind, given the number of samples and the duration of the study.
• The findings of the study show high levels of multi-drug resistant strains amongst equine pathogens. This points to the urgent necessity for responsible use of antibiotics in veterinary practices, also known as antimicrobial stewardship.