Alterations in the cecal microbiome of New Zealand White rabbits due to the long-acting anticoagulant rodenticide brodifacoum

Long-acting anti-coagulant rodenticides (LAARs) are well characterized with respect to inhibition of vitamin K1 synthesis and effects on blood coagulation. However, effects of LAARs on the microbiome have not been explored. We administered brodifacoum (BDF), one of the more potent LAARs, to adult male New Zealand White rabbits, and carried out 16S RNA sequencing on cecal samples collected after different times. Samples were also obtained from rabbits treated with the bile sequestrant cholestyramine (CSA) which accelerates BDF clearance from the body, and from CSA-only treated rabbits. We collected blood samples after different times and used mass spectroscopy to measure plasma levels of L-arginine and related molecules. Changes at both the phylum and genus levels in relative abundance were observed after 2 and 3 days exposure to BDF. The majority of those microbiota changes were prevented by co-treatment with CSA. Identification of metabolic pathways potentially altered by BDF using Picrust2 identified several L-arginine-related pathways. Exposure to BDF caused increases in plasma L-arginine concentration as well as nitrites, suggesting increased activity of nitric oxide synthase. We also observed increases due to BDF in plasma concentrations of L-arginine-related molecules including L-citrulline, L-ornithine, and methylated L-arginines ADMA and NMMA. These results demonstrate that LAAR poisoning can induce microbiome dysbiosis and influence metabolic pathways and metabolites involved in inflammation and vasodilation.