Characterizing antimicrobial activity of environmental <i>Streptomyces</i> spp. and oral bacterial and fungal isolates from <i>Canis familiaris</i> and <i>Felis catus</i>

The emergence and spread of antimicrobial resistance presents a global health challenge. As such, researchers are focused on developing pipelines to discover novel antimicrobials. In this study, we screened two distinct collections of microbes for antimicrobial activity. First, we collected bacterial and fungal isolates from the oral cavities of domesticated dogs and cats and identified these isolates using 16S (bacteria) and ITS (fungi) sequencing. Follow-up analyses confirmed that some conditioned media from bacterial isolates had antibacterial activity against <i>Escherichia coli</i> and antifungal activity against <i>Candida albicans</i> both alone and in combination with the current antimicrobial drugs. Additionally, screening 32 predicted or confirmed Streptomyces environmental isolates for antifungal and antibacterial activity identified two isolates with antifungal activity (WAC5038 and WAC5287), with only one isolate demonstrating antibacterial activity (WAC5038). Overall, this study provides a framework to identify and characterize environmental microbes with antimicrobial activity.