Microbiota Analysis and Characterisation of the Novel Limosilactobacillus Strains Isolated from Dogs

<b>Background/Objectives:</b> The growing number of households with companion dogs raises concerns. Co-living environments between companion dogs and their owners are linked to a heightened risk of cross-infections from strains such as <i>Escherichia coli</i> (<i>E. coli</i>), <i>Staphylococcus aureus</i> (<i>S. aureus</i>), <i>Salmonella</i>, and faecal coliforms. Therefore, this study aims to propose measures for healthy cohabitation by analysing the faecal microbiota of puppies and adult dogs. <b>Methods:</b> We isolated lactic acid bacteria (LAB) from their faeces and assessed their potential to inhibit <i>E. coli</i>, <i>S. aureus</i>, and <i>Salmonella</i> spp. Faecal samples from puppies (<2 months old) and adult dogs (>12 months old) were analysed and compared. <b>Results:</b> The analysis revealed that <i>Lactobacillus</i> dominated puppy faeces, while <i>Bacteroidetes</i> were more abundant in adult dogs. In total, 109 primary LAB candidates were isolated from faecal samples. These isolates underwent secondary screening for acid tolerance, bile salt resistance, acid production, heat resistance, protease activity, and antimicrobial activity against <i>E. coli</i>, <i>S. aureus</i>, and <i>Salmonella</i> spp. Five secondary LAB candidates with probiotic potential were further characterised via morphological and genetic analysis. All five strains were <i>Lactobacillus reuteri</i>, with <i>L. reuteri</i> JJ37, JJ68, JJ69, JJ71, and JJ77 emerging as the final probiotic candidates. <b>Conclusions:</b> They promote healthier cohabitation between dogs and their owners.