Practical media formulations for rapid growth of Lactobacillus iners and other vaginal bacteria

Vaginal microbiome composition is closely tied to host health. A microbiome dominated by specific anaerobes (e.g., Gardnerella vaginalis ) is termed bacterial vaginosis (BV) and is associated with negative health outcomes, while colonization by Lactobacillus species is thought to protect against BV. However, the role of the species Lactobacillus iners in vaginal health is controversial, with evidence that some strains may not protect against BV while others do. To better characterize L. iners strains, their interactions with vaginal bacteria and human cells need to be investigated in vitro , but this has been impeded by the lack of liquid media for rapid L. iners growth. We have developed three liquid media formulations for L. iners growth: Serrador’s Lactobacilli-adapted Iscove’s Medium (SLIM) which leads to robust L. iners growth, a vaginally adapted version of SLIM (SLIM-V) and a chemically defined medium (SLIM-CD). SLIM and SLIM-V lead to dramatically improved L. iners growth compared to previously published formulations and support growth of other vaginal bacteria, including L. crispatus, L. jensenii, L. gasseri and G. vaginalis . SLIM-CD leads to slower growth but could prove useful for characterizing L. iners nutrient requirements or metabolite production. A modified version of SLIM-V supports growth of human cervical epithelial cells and provides a base for future co-culture work. Here, we present the formulations of SLIM, SLIM-V and SLIM-CD, and compare the growth of bacterial strains and human cells in the media.