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
Frequently asked questions
What is Lactobacillus species?
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.
What is the Gram stain of Lactobacillus species?
Lactobacillus species is Gram positive.
What are the lab clues for Lactobacillus species?
Lab clues for Lactobacillus species include Gram-positive rods (Doderlein bacilli), Catalase-negative, Lactic-acid fermentation, and Non-spore-forming.
What is Lactobacillus species commonly confused with?
Lactobacillus species is commonly confused with Gardnerella vaginalis and Listeria monocytogenes.
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.