Evaluating the Adjuvant Therapeutic Effects of Probiotic Strains Lactococcus cremoris and Lacticaseibacillus paracasei on Canine Atopic Dermatitis and Their Impact on the Gut and Skin Microbiome

This study investigated the therapeutic potential of a novel probiotic combination consisting of <i>Lactococcus cremoris</i> subsp. <i>cremoris</i> MP01 and <i>Lacticaseibacillus paracasei</i> subsp. <i>paracasei</i> MP02, collectively referred to as LCP, in the treatment of canine atopic dermatitis (CAD). In a 60-day open-label, single-arm trial involving eight dogs, notable clinical improvements were observed following daily LCP treatment, as evidenced by decreasing trends in Canine Atopic Dermatitis Extent and Severity Index and Pruritus Visual Analogue Scale scores, as well as a significant reduction in serum immunoglobulin E levels (<i>p</i> < 0.05). Microbiome and short-chain fatty acid (SCFA) analyses were subsequently conducted in a representative subset of six dogs to explore the effects of LCP on the fecal and skin microbial ecosystems. Concomitant alterations in gut and skin microbiome were observed, including a significant reduction in abundance of <i>Erysipelotrichaceae</i> (<i>p</i> < 0.05) and non-significant decreasing trends in <i>Romboutsia</i>, <i>Escherichia</i>/<i>Shigella</i> spp., and <i>Shigella flexneri</i>, along with a trend toward increased SCFA production. Functional prediction using PICRUSt suggested potential involvement of immune- and infection-related signaling pathways, including those associated with nucleotide-binding oligomerization domain-like receptors, retinoic acid-inducible gene I-like receptors and Shigellosis, supporting the hypothesis that LCP may exert its effects through modulation of the gut-skin axis. These findings support LCP as a safe and promising adjunct therapy for CAD, offering a novel microbiome-targeted approach targeting both clinical symptoms and underlying dysbiosis. Further investigation is warranted to optimize probiotic formulations and better understand the mechanisms underlying microbiome-mediated immune modulation in canine allergy.