Antimicrobial resistance in clinical bacterial isolates from horses in the UK

Abstract

Background: Surveillance of antimicrobial resistance (AMR) in horses is important to aid empirical treatment decisions and highlight emerging AMR threats. Objective: To describe the AMR patterns of common groups of bacteria from clinical submissions from horses in the UK during 2018, and to determine how this varies by sample site and type of submitting veterinary practice. Study design: Prospective observational study. Methods: All data on bacterial culture and subsequent antimicrobial susceptibility testing (AST) collected in 2018 from six large equine diagnostic laboratories were included. Resistance patterns were analysed including resistance to 1 or 2 antimicrobial classes, multidrug resistance (MDR), extensively drug resistant (XDR), resistance to highest priority critically important antimicrobials and isolates where there was no readily available treatment for adult horses in the UK. Submitting practices were classified according to whether they treated referral cases or not (first opinion). Comparisons between proportions and resistance for each bacterial group and sample site was performed using Chi squared (or Fisher's exact test). Results: A total of 6018 bacterial isolates from 4038 diagnostic submissions were included from respiratory (n=1555), urogenital (n=1010), skin/hair/wound/abscess (n=753), surgical site infection (SSI) /catheterrelated-infection (CRI) /orthopaedic infections (n=347) and unknown/'other' submissions (n=373). There were 2711 Gram-negative isolates and 3307 Gram-positive isolates. Prevalence of MDR for E. coli was 31.7%, Staphylococcus spp. 25.3% and >25% for the majority of bacterial isolates from SSI/CRI/orthopaedic submissions. For Enterococcus spp. there was no readily available treatment for adult horses in the UK in 30.2% of positive submissions. MDR was significantly higher from referral hospital than first opinion submissions for the majority of pathogens (except Actinobacillus spp. and Pasteurella spp. and β-haemolytic Streptococcus spp.). Main limitations: Since culture and susceptibility results are not systematic analyses based on harmonised methods, selection bias could impact the findings. Conclusions: Ongoing surveillance is essential to understand emerging patterns of resistance. MDR is high in SSI/CRI/orthopaedic infections, which is important for hospital biosecurity and guiding treatment decisions. Harmonisation of diagnostic procedures and interpretation of results amongst veterinary laboratories will improve AMR surveillance and data comparison amongst laboratories.

Improving clinical outcomes via responsible antimicrobial use in horses

“…Good communication and closer collaboration between the clinician and the microbiologist are essential to optimise patient outcomes. Perhaps, it is no surprise that in 8.6% of the diagnostic submissions to the laboratories in a recent project, the sample site was not recorded (Isgren et al 2021). This is particularly frustrating when many of the bacterial isolates from these unknown sample sites were MDR.…”

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial‐resistant Escherichia coli in dogs and cats, horses, swine, poultry, cattle, sheep and goats

“…Horses. In horses ( Equus caballus ), E. coli has been mostly associated with urinary and reproductive infections, respiratory diseases and infections of soft tissues and wounds (Maddox et al, 2015 ; SVARM, 2020 ; Isgren et al, 2021 ).…”

“…Recent publications from France have reported susceptibility patterns from a variety of bacteria from clinical submissions from 2012 to 2016 and identified increasing resistance to trimethoprim–sulfamethoxazole in E. coli (Isgren et al, 2021 ). Another report from France identified a decrease in MDR E. coli clinical isolates from 2006 to 2016; however, prevalence of MDR still remained above 22.5% for E. coli (Isgren et al, 2021 ). The proportion of resistance reported in a study performed in the UK, involving six large equine diagnostic laboratories, and including 958 clinical E. coli isolates, is presented in Table 3 (Isgren et al, 2021 ).…”

“…Another report from France identified a decrease in MDR E. coli clinical isolates from 2006 to 2016; however, prevalence of MDR still remained above 22.5% for E. coli (Isgren et al, 2021 ). The proportion of resistance reported in a study performed in the UK, involving six large equine diagnostic laboratories, and including 958 clinical E. coli isolates, is presented in Table 3 (Isgren et al, 2021 ).…”

An equine veterinary surveillance network for the UK horse population

“…However, the use of government laboratories and submissions from horses are low and hence this is unlikely to accurately reflect the UK horse population. Equine clinicians more frequently utilise private and commercial laboratories and the value of these data in monitoring antimicrobial resistance patterns of relevant bacteria in equids has recently been demonstrated, 15 although ongoing surveillance is now needed to understand emerging and changing patterns of resistance.…”