LACTOBACILLUS

102 plus species divided into 3 groups (including):

SPECIES

Group I - obligate homofermentatives
Lactobacillus acidophilus
Lactobacillus bulgaricus
Lactobacillus delbruekii
Lactobacillus leichmannii



Group II - facultative heterofermentatives
Lactobacillus casei
Lactobacillus plantarum

Group III - obligate heterofermentatives
Lactobacillus brevis
Lactobacillus fermentum

MICROSCOPIC APPEARANCE

Gram Stain: Positive.
Morphology: Long, slender rods to short, coryneform coccobacilli.
Size: 0.5-1.2 micrometers by 1.0-10.0 micrometers.
Motility: Non-motile, rarely showing motility by peritrichous flagella.
Capsules: None.
Spores: None.

MACROSCOPIC APPEARANCE

Typically colonies on agar media are usually 2-5 micrometers, convex, entire, opaque, and without pigment. Many test reactions are weak and dependent on the composition of the media and exact cultural conditions. Thus, special expertise may be required for identification of species.

KEY BIOCHEMICAL REACTIONS

METABOLIC PROPERTIES

Facultatively anaerobic, microaerophilic, or facultatively aerobic. Metabolism is fermentative and saccharoclastic; using sugar as carbon sources, with at least half the end product of carbon being lactate.

HABITAT

Part of the normal flora of mouth, intestinal tract and vagina of humans and other warm-blooded animals. Also found in dairy meat, fish, pickled and fermented products.

PATHOGENICITY

Apart from dental caries, lactobacilli are generally considered to be apathogenic. However, there is an increasing number of reports that lactobacilli have been involved in human diseases. Mainly L. casei subsp. rhamnosus , but also L. acidophilus , L. plantarum and occasionally L. salivarius have been found to be associated with subacute bacterial endocarditis, systemic septicemia and abscesses. (2)

RECOMMENDED MEDIA

For culture: Rich, complex media.
For selective isolation: Universal Beer Agar, MRS Agar and Broth.
For maintenance: Skim Milk Media may be used for storage at -70 degrees C.
Lyophilization may be used for preservation.

INCUBATION

Temperature: 28-30 degrees C.
Time: 3-4 days.
Atmosphere: Anaerobic or in 10% CO 2 .

REFERENCES

1. Holt, J.G., et al. 1994. Bergey's Manual of Determinative Bacteriology , 9th ed. Williams & Wilkins, Baltimore, MD.

2. Holt, J.G., et al. 1986. Bergey's Manual of Systemic Bacteriology , Vol. I & II. Williams & Wilkins, Baltimore, MD.

3. The Oxoid Vade-Mecum of Microbiology . 1993. Unipath Ltd., Basingstoke, UK.

4. Murray, P.R., et al. 1995. Manual of Clinical Microbiology , 6th ed. American Society for Microbiology, Washington, D.C.

5. Internet: www.hardlink.com /Bacterial Database Search, February, 1998.

6. Hensyl, B.R., et al. 1990. Stedman's Medical Dictionary , 25th ed. Williams & Wilkins, Baltimore, MD.

7. Koneman, et al. 1997. Color Atlas and Textbook of Diagnostic Microbiology , 5th ed. Lippincott, Philadelphia, PA.


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