Ex-vivo investigation of human salivary microbial growth with lysogeny broth for translational research–A pilot study

Background/purpose: Salivary microbiome has become a surrogate indicator of oral disease due to its collective reservoirs and convenience in sampling. However, failed clinical trials often lead to wastes of resources, indicating a need for preclinical models. In this pilot study, we aimed to compare the salivary microbiome by metagenomics analysis before and after lysogeny broth culture for prospective translational studies. Materials and methods: The study cohort included seven patients with severe periodontitis (Stage III/IV, Grade C), from whom unstimulated saliva was collected. The salivary microbiome was sequenced over the 16S rRNA gene V3–V4 hypervariable regions at baseline and after 6 hours of lysogeny broth culture. Results: The results revealed changes in salivary microbiome and reduced bacterial diversity after culture, mainly due to the expansion of genera Neisseria (Median (Mdn) 15.95% to 37.52%, P < 0.05), Rothia (Mdn 10.21% to 16.32%, P < 0.05), and Haemophilus (Mdn 5.88% to 13.25%, P < 0.05). Periodontitis-related pathogens such as phyla Bacteroidetes, Fusobacteria and Spirochaetes were identified, while genera Porphyromonas, Parvimonas, Peptostreptococcus, and Campylobacter showed a decrease after lysogeny broth culture. Caries-related pathogens, including genera Veillonella, Leptotrichia, and species Haemophilus parainfluenzae and Streptococcus salivarius, were also detected. Conclusion: This pilot study revealed that periodontitis- and caries-related bacteria could be identified in the saliva at baseline and after 6 hours ex-vivo culture with lysogeny broth. Our findings also suggested that lysogeny broth favored the growth of specific genera and may serve as a reference to monitor short-term modulation of these bacteria in salivary microbiome.