Bacterium
Lactobacillus species
Doderlein vaginal-flora acid producer
lak-toh-buh-SIL-us
High-yield clue
Dominant healthy vaginal flora that produces lactic acid (and hydrogen peroxide) to keep a low pH; their loss allows bacterial vaginosis.
Overview
Gram-positive, catalase-negative rods (Doderlein bacilli) that dominate the healthy vaginal microbiota and are minor members of normal gut and oral flora. They are the classic teaching example of protective acid-producing normal flora.
Classification
- Gram-positive
- Rod
- Facultative/aerotolerant anaerobe
- Catalase-negative
- Lactic-acid producer
Lab & identification clues
- Gram-positive rods (Doderlein bacilli)
- Catalase-negative
- Lactic-acid fermentation
- Non-spore-forming
Associations
- Normal vaginal and gut flora
- Protective acidification of the vagina
- Fermentation / probiotic study framing
Commonly confused with
- Gardnerella vaginalis
- Listeria monocytogenes
Your notes
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.