Antibacterial Activity of Endophytic Streptomyces spp. isolated from Medicinal Plants of Dental Importance

Wide variations of plant species in Malaysia provide suitable hosts for the isolation of endophytic streptomycetes, which can be potential sources of bioactive compounds with therapeutic applications in dentistry. Objectives: This study’s objectives were to isolate endophytic streptomycetes from medicinal plants and to evaluate their antibacterial activity against Streptococcus mutans, a key pathogen responsible for dental caries. Methods: Endophytic streptomycetes were isolated from seven fresh plants: Mauritius papeda (Kaffir lime), Cosmos caudatus (Ulam Raja plant), Lawsonia inermis (Henna plant), Piper sarmentosum (Kadok), Kaempferia galanga (Cekur plant), Ziziphus mauritiana (Bidara plant), and Psidium guajava (Guava plant), using a surface-sterilization method. Different plant parts were placed on five isolation media, namely Water Agar, International Streptomyces Project (ISP) 2, ISP 4, ISP 5, and Tap Water Yeast Agar, and incubated at 37°C for up to one month. Isolates were identified by morphological characteristics and tested for antimicrobial activities through a cross-streak assay. Results: A total of 38 endophytes were successfully isolated, with 19 identified as streptomycetes. Specifically, seven, two, five, and three endophytes were isolated from stem, root, leaf, and fruit, respectively. Three endophytic streptomycetes exhibited antagonistic activity against S. mutans. Conclusion: Endophytic streptomycetes demonstrated antibacterial activity against S. mutans, indicating their potential for further development in dental applications.