Efficacy of Heat‐Killed Lactobacillus plantarum L‐137 Supplementation in Treatment of Canine Atopic Dermatitis

BACKGROUND: Canine atopic dermatitis (cAD) is a chronic inflammatory skin disease and has been associated with gut dysbiosis. HYPOTHESIS/OBJECTIVES: To evaluate the efficacy of heat-killed Lactobacillus plantarum L-137 (HK L-137), a postbiotic supplementation in managing cAD. ANIMALS: Twelve client-owned dogs with cAD. MATERIALS AND METHODS: A randomised, placebo-controlled, double-blinded crossover trial. Dogs were divided into two groups (n = 6) and received oral HK L-137 or placebo once daily for 12 weeks. After a 2-week washout period, they received the alternative treatment. Oral oclacitinib (0.4-0.6 mg/kg once daily) was permitted throughout the study. Clinical severity was assessed with the 4th iteration of the cAD Extent and Severity Index (CADESI-04) and owner-evaluated pruritus Visual Analog Scale (PVAS) and faecal scoring at 0, 12, 14 and 26 weeks. Serum concentrations of C-reactive protein (CRP), interleukin (IL)-4, interferon-gamma (IFN-γ) and C-C motif chemokine ligand 17 (CCL17), and haematological and biochemical findings were analysed at the same time points. Faecal microbiota composition (genomic DNA) was assessed at 12 and 26 weeks. RESULTS: PVAS scores mildly improved in both groups, with greater reduction in the HK L-137 group, yet this was not statistically significant. Serum CRP concentrations increased significantly in the control group (p = 0.02). Serum CCL17 concentrations decreased significantly in the HK L-137 group (p = 0.01). No significant changes were observed in CADESI-04, IL-4, IFN-γ or faecal scores or faecal microbiota diversity and composition. CONCLUSIONS AND CLINICAL RELEVANCE: HK L-137 represents a potential, well-tolerated adjunctive therapy for dogs with cAD. Therapy was associated with reduced CCL17. Further studies with fewer variables are indicated.