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

Abstract Objectives The aim of this study was to analyze the evolution of the antimicrobial susceptibility of equine pathogens isolated from clinical samples from 2006 to 2016. Methods A collection of 25,813 bacterial isolates were studied, clustered according to their origins (respiratory tract, cutaneous, genital and other) and analyzed for their antimicrobial susceptibility using the disk diffusion method. Results The most frequently isolated pathogens 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%). 9,512 isolates were from respiratory samples (36.8%), 7,689 from genital origin (29.8%) and 4,083 from cutaneous samples (15.8%). Over the 11-year period, the frequency of multidrug-resistant (MDR) strains fluctuated between 6.4% and 20.4% for group C Streptococci and between 17% and 37.7% for K. pneumoniae . From 2006 to 2009, 24.5% to 43.0% of S. aureus isolates were MDR, after 2009 the level did not exceeded 27.6%. For E. coli and Enterobacter s pp, these levels were mostly higher than 30.0% until 2012 but significantly decreased thereafter (22.5% to 26.3%). Conclusions This study is the first large scale analysis of equine pathogens both by the number of samples and the duration of the study. Our results pointed out the presence of high level of MDR strains and the need to support veterinary antimicrobial stewardship to encourage proper use of antibiotic.