The Effects of Bacillus licheniformis—Fermented Products on the Microbiota and Clinical Presentation of Cats with Chronic Diarrhea

SIMPLE SUMMARY: Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer a health benefit to the host. Probiotics have also been introduced in companion animals in recent years, and the main priority of probiotic use has focused on the health of individual animals. This study aimed to compare the fecal microbiota of cats with chronic diarrhea with that of healthy cats from the same household and evaluate the effectiveness of oral administration of Bacillus licheniformis-fermented products (BLFP) in relieving clinical signs and altering the intestinal microbiota in diarrheal cats. Overall, this study provides basic information on the types and ratios of fecal microbiota in healthy cats and cats with chronic diarrhea. Our results also demonstrated that oral administration of BLFP could significantly impact the relief of clinical gastrointestinal symptoms and the gastrointestinal microbiomes in cats with diarrhea. ABSTRACT: Bacillus licheniformis-fermented products (BLFP) are probiotics with antibacterial, antiviral, and anti-inflammatory properties that can improve growth performance. This study aimed to compare the fecal microbiota of diarrheal cats with chronic diarrhea (n = 8) with that of healthy cats (n = 4) from the same household using next-generation sequencing, and evaluate the effectiveness of oral administration of BLFP in relieving clinical signs and altering the intestinal microbiota in diarrheal cats. Six out of eight diarrheal cats showed clinical improvement after BLFP administration for 7 days, and the stool condition of the other two was normal. A higher Firmicutes/Bacteroidetes ratio was noted in the feces of diarrheal cats without clinical improvement as compared with those in the healthy cats and in the diarrheal cats with clinical improvement after receiving BLFP. The phylum Bacteroidetes and class Bacteroidia decreased significantly in diarrheal cats regardless of BLFP administration. Blautia spp., Ruminococcus torques, and Ruminococcus gnavus, which belong to the Clostridium cluster XIVa and have been reported as beneficial to intestinal health, increased significantly in feces after treatment. Furthermore, Clostridium perfringens also significantly decreased in diarrheal cats after BLFP administration. Overall, BLFP could be a potential probiotic to relieve gastrointestinal symptoms and improve fecal microbiota in cats with chronic diarrhea.