Nebulization of 2% lidocaine has no detectable impact on the healthy equine respiratory microbiota.
Authors: Holley Lauren, Creasey Hannah N, Bedenice Daniela, Reed Sarah, Romualdo da Silva Debora Regina, Trautwein Victoria, Mazan Melissa, Widmer Giovanni
Journal: PloS one
Summary
# Editorial Summary: Nebulized Lidocaine and the Equine Respiratory Microbiota As glucocorticosteroids remain the standard treatment for equine asthma but carry risks of microbiome disruption and other side effects, researchers investigated whether nebulized 2% lidocaine might offer a safer alternative by assessing its impact on the healthy respiratory microbiota. Using a randomized, blinded, crossover design, 1 mg/kg doses of 2% lidocaine were administered via nebulization seven times over four days, with respiratory samples collected from multiple sites (nasal wash, endoscopic tracheal aspirate, and bronchoalveolar lavage fluid) and analysed using 16S amplicon sequencing to profile bacterial communities. Lidocaine treatment produced no clinically detectable changes and did not alter either nasal or tracheal microbiota composition in healthy horses, though temporal factors accounted for 12.6% of microbiota variation; notably, distinct bacterial profiles emerged between sampling sites, with Actinobacteria predominating in nasal samples and Firmicutes in tracheal samples. The finding that bronchoalveolar lavage fluid yielded insufficient bacterial DNA for analysis despite multiple extraction and PCR approaches confirms that healthy equine lungs naturally harbour extremely low bacterial loads. For practitioners considering lidocaine nebulization as part of an asthma management strategy, this evidence suggests the treatment poses no risk of disrupting the healthy respiratory microbiota, though further work in clinically affected horses is needed to establish therapeutic efficacy.
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Practical Takeaways
- •Lidocaine nebulization appears microbiologically safe as an alternative to glucocorticosteroids for asthma treatment, without disrupting the healthy respiratory bacterial community
- •Clinical assessment and respiratory sampling site selection matter—nasal and tracheal samples yield different microbial profiles and should not be used interchangeably
- •Lower respiratory tract sampling in healthy horses may require specialized protocols due to low bacterial density
Key Findings
- •2% lidocaine nebulization (1 mg/kg, 7 treatments over 4 days) did not alter tracheal or nasal microbiota in healthy horses
- •Significant compositional differences exist between nasal and tracheal microbiota, with Actinobacteria dominant nasally and Firmicutes dominant tracheally
- •Time accounted for 12.6% of microbiota variation among samples
- •Bronchoalveolar lavage fluid from healthy horses has low bacterial load, with insufficient DNA for standard 16S amplicon sequencing