The effect of different antimicrobial treatment regimens on the faecal shedding of ESBL-producing Escherichia coli in horses.

Fourth-generation cephalosporins can select for extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae in horses, but it is unknown to what extent this occurs compared to penicillin/gentamicin combination treatment. The objective was to evaluate the effect of different antimicrobial treatments on faecal shedding and diversity of ESBL-producing Escherichia coli (ESBL-EC) in horses. Upon hospital admission, 86 horses in need of antimicrobial treatment or prophylaxis were randomly allocated to receive penicillin and gentamicin (PG) or cefquinome (CEF). Untreated horses were included as controls (NOAMD, n = 33). Faecal samples from admission (T1), 3 days after admission (T2), and faecal swabs 28 days after discharge (T3) were cultured selectively. Differences in prevalence (T1, T2, T3) and counts (T1, T2) of ESBL-EC between groups and over time were analysed. On a subset of ESBL-EC isolates, antimicrobial susceptibility testing (n = 45) and whole-genome sequencing followed by SNP-analysis (n = 46) were performed. The prevalence of ESBL-EC at T1 was 12 % with no significant difference between groups. In all groups, significantly higher carriage rates were observed at T2 and T3 compared to T1. Carriage and counts of ESBL-EC at T2 were significantly higher in treated compared to untreated horses. There was no significant difference between PG and CEF at any time points. Despite a large genetic diversity, indistinguishable ESBL clones were observed in different horses over time. In conclusion, antimicrobial treatment and hospitalization increased prevalence and counts of ESBL-EC, and transmission of ESBL-EC in the hospital was suspected. These findings highlight the importance of antimicrobial stewardship and infection control practices in equine medicine.

A retrospective analysis of antimicrobial resistance in bacterial pathogens in an equine hospital (2012-2015).

INTRODUCTION: Antimicrobial resistance has become an important concern in veterinary medicine. The aim of this study was to describe the rate of antimicrobial resistance in common equine pathogens and to determine the occurrence of multidrug-resistant isolates. A retrospective analysis of all susceptibility testing results from bacterial pathogens cultured from horses at the University of Zurich Equine Hospital (2012-2015) was performed. Strains exhibiting resistance to 3 or more antimicrobial categories were defined as multidrug-resistant. Susceptibility results from 303 bacterial pathogens were analyzed, most commonly Escherichia coli (60/303, 20%) and Staphylococcus aureus (40/303, 13%). High rates of acquired resistance against commonly used antimicrobials were found in most of the frequently isolated equine pathogens. The highest rate of multidrug resistance was found in isolates of Acinetobacter baumannii (23/24, 96%), followed by Enterobacter cloacae complex (24/28, 86%) and Escherichia coli (48/60, 80%). Overall, 60% of Escherichia coli isolates were phenotypically ESBL-producing and 68% of Staphylococcus spp. were phenotypically methicillin-resistant. High rates of acquired antimicrobial resistance towards commonly used antibiotics are concerning and underline the importance of individual bacteriological and antimicrobial susceptibility testing to guide antimicrobial therapy. Minimizing and optimizing antimicrobial therapy in horses is needed.

INTRODUCTION: Une connaissance des bactéries pathogènes présentes localement est importante pour pouvoir mettre en œuvre dès le début un traitement antibiotique ciblé. Le but de cette étude était de décrire les agents infectieux les plus fréquents et leur évolution dans le temps chez les chevaux hospitalisés à l'hôpital vétérinaire de Zürich entre 1988 et 2014. Tous les résultats positifs de cultures ont été analysés rétrospectivement. Les isolats ont été classés sur la base de leur localisation, du diagnostic et de l'année de leur isolation. Diverses périodes ont été comparées au moyen d'un test de chi carré. Escherichia coli (299/1'723, 17%), Streptococcus equi ssp. zooepidemicus (295/1'723, 17%) et les staphylocoques coagulase positive (196/1'723, 11%) ont été dans l'ensemble les bactéries mises en évidence le plus souvent. Des bactéries anaérobes strictes ont été trouvées principalement dans les infections dentaires (18/66, 27%), les péritonites (6/43, 14%) et les infections des tissus mous (28/208, 13%). Des cultures mixtes étaient particulièrement fréquentes dans les infections cutanées et dentaires (24/55, 44% et 17/43, 40%). Les principaux germes isolés dans la plupart des systèmes d'organes étaient aussi bien Gram positifs que Gram négatifs. Pour cette raison, il conviendrait, jusqu'à ce que les résultats des cultures et des antibiogrammes soient connus, de choisir un médicament à large spectre d'action.