Disclosed are methods for diagnosing Bacterial Vaginosis (BV). The disclosed methods generally include detecting select species of Eggerthella and/or Prevotella, and optionally detecting select species of Lactobacillus. Also disclosed are nucleic acid oligomers and related compositions for detection of a 16S rRNA or its encoding gene from select species of Eggerthella, Prevotella, or Lactobacillus.