Meaning of lactobacillus: Lactobacillus is a genus of bacteria that produces lactic acid and normally lives harmlessly in the human gut, mouth, and vaginal tract.

Definition of lactobacillus

Lactobacillus is a genus of rod shaped bacteria that produce lactic acid as they ferment sugars, giving the group its name. These bacteria are normal inhabitants of the human gastrointestinal tract, mouth, and vaginal tract, where they generally live without causing disease.

Lactobacillus species are widely used outside the body as well, particularly in the fermentation of foods such as yogurt, cheese, sauerkraut, and other cultured products, where their lactic acid production contributes to flavor, texture, and preservation.

Certain lactobacillus strains are marketed as probiotic supplements intended to support a healthy balance of gut or vaginal bacteria. Although lactobacilli are generally considered harmless, they can contribute to tooth decay and, in people with a weakened immune system, occasionally cause infection.

Used in a sentence

Vaginal culture identified lactobacillus as part of the normal bacterial flora.

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Good to know

Lactobacillus is generally regarded as a harmless, even beneficial, member of the body's normal bacterial population, so its presence on a culture is not by itself evidence of infection.

Word origin

Where “lactobacillus” comes from

Formed from Latin lac, lactis, meaning milk, and bacillus, meaning little rod, from baculus, meaning staff or rod.

For learning, not diagnosis. This glossary provides general educational information and is not a substitute for advice from a qualified healthcare professional. If you may be experiencing a medical emergency, contact local emergency services.