Antimicrobial resistance among Streptococcus equi subspecies zooepidemicus and Rhodococcus equi isolated from equine specimens submitted to a diagnostic laboratory in Kentucky, USA

Pilot study characterizing a single pooled preparation of equine platelet lysate for nebulization in the horse

Introduction

Platelet lysate (PL) demonstrates antimicrobial and anti-inflammatory properties offering potential for treatment of bacterial pneumonia in horses. It remains unknown whether nebulization is suitable for PL administration in horses. This pilot study characterized particle size and flow rate of pooled equine PL (single preparation) nebulized using an equine-specific nebulizer (Flexivent®).

Methods

Protein composition and antimicrobial activity were compared before and after nebulization. Protein composition was evaluated according to growth factor, antimicrobial peptide and cytokine concentrations and proteomic analysis. To evaluate antimicrobial activity, bacterial growth inhibition [maximum growth (μmax); carrying capacity (K)] were determined for E. coli, Streptococcus equi subsp zooepidemicus and Rhodococcus equi (WT and MDR) using pre- and post-nebulized PL concentrations of 50%.

Results

Flow rate and median particle size were 0.8 ml/min and 4.991 μm with 52% of particles ≤ 5 μm. Differences in PL protein composition were detected with nebulization. For E. coli and S. zooepidemicus, nebulization did not alter effect of PL on growth parameters. PL treatments decreased K for S. zooepidemicus (p = 0.009) compared to BHI. For R. equi K was increased post- vs. pre-nebulization (WT and MDR) and μmax increased pre- vs, post-nebulization (MDR). PL treatments increased K and μmax for MDR R. equi and μmax for WT R. equi compared to BHI (p ≤ 0.05).

Conclusion

Nebulization of PL in vitro is technically feasible. The results of this study support further investigation to better characterize the effect of nebulization on PL and its suitability for nebulization in horses.

Antimicrobial Resistance in Equines: A Growing Threat to Horse Health and Beyond-A Comprehensive Review

The equine industry holds substantial economic importance not only in the USA but worldwide. The occurrence of various infectious bacterial diseases in horses can lead to severe health issues, economic losses, and restrictions on horse movement and trade. Effective management and control of these diseases are therefore crucial for the growth and sustainability of the equine industry. While antibiotics constitute the primary treatment strategy for any bacterial infections in horses, developing resistance to clinically important antibiotics poses significant challenges to equine health and welfare. The adverse effects of antimicrobial overuse and the escalating threat of resistance underscore the critical importance of antimicrobial stewardship within the equine industry. There is limited information on the epidemiology of antimicrobial-resistant bacterial infections in horses. In this comprehensive review, we focus on the history and types of antimicrobials used in horses and provide recommendations for combating drug-resistant bacterial infections in horses. This review also highlights the epidemiology of antimicrobial resistance (AMR) in horses, emphasizing the public health significance and transmission dynamics between horses and other animals within a One Health framework. By fostering responsible practices and innovative control measures, we can better help the equine industry combat the pressing threat of AMR and thus safeguard equine as well as public health.

Rhodococcus equi: challenges to treat infections and to mitigate antimicrobial resistance

Rhodococcus equi, a gram-positive facultative intracellular pathogen and a soil saprophyte, is one of the most common causes of pneumonia in young foals. It poses a threat to the economy in endemic horse-breeding farms and to animal welfare annually. Many farms use thoracic ultrasonographic screening and antimicrobial treatment of subclinically affected foals as a preventive measure against severe R. equi infections. The wide use antimicrobials to treat subclinically affected foals has contributed to the emergence of multidrug resistant (MDR)-R. equi in both clinical isolates from sick foals and in the environment of horse-breeding farms. Alternatives to treat foals infected with MDR-R. equi are scarce and the impact of the emergence of MDR-R. equi in the environment of farms is still unknown. The aim of this review is to discuss the emergence of MDR-R. equi in the United States and the challenges faced to guide antimicrobial use practices. Reduction of antimicrobial use at horse-breeding farms is essential for the preservation of antimicrobial efficacy and, ultimately, human, animal, and environmental health.