Cat. no. C6050 CRITERION™ Lactobacillus Selective (LBS) Agar Base 168gm
Cat. no. C6051 CRITERION™ Lactobacillus Selective (LBS) Agar Base 500gm
Cat. no. C6052 CRITERION™ Lactobacillus Selective (LBS) Agar Base 2kg
Cat. no. C6053 CRITERION™ Lactobacillus Selective (LBS) Agar Base 10kg
Cat. no. C6054 CRITERION™ Lactobacillus Selective (LBS) Agar Base 50kg


Hardy Diagnostics CRITERION™ Lactobacillus Selective Agar Base is recommended as a general purpose growth medium for the selective isolation, cultivation, and enumeration of lactobacilli.

This dehydrated culture medium is a raw material intended to be used in the making of prepared media products, which will require further processing, additional ingredients, or supplements.


Lactobacilli (LAB) are gram-positive, non-sporing, bacilli that microscopically appear in chains varying from long, slender, and sometimes bent, to short and often coryneform-like. Pigment is rarely produced, but if present colonies can range from yellow, orange to rust, or brick in color. As lactobacilli are mostly microaerophilic, surface growth is enhanced by anaerobiosis or lowered oxygen pressure or enhanced CO2 (5-10%). Lactobacilli grow best in acidic media with a pH range of 4.5-6.4 and exhibit a wide temperature range, from 2 to 53ºC, but prefer temperatures from 30 to 40ºC.(2,4) Lactobacilli are part of the normal flora in the mouth, intestinal tract and vagina of animals. Aside from dental caries, they are rarely considered pathogenic. They are important to the food, dairy and beverage industries both in the production and spoilage of products.(4)

Lactobacilli are significant contaminants in the food, dairy, and beverage industries. Although lactobacilli are found on plant surfaces in low numbers, they grow luxuriously in all decaying plants and especially fruits.(4) The microbial spoilage of unpasteurized fruit juices is most often the result of lactobacilli. Due to their preference for acidic environments, even citrus concentrates can be spoiled with acetylmethylcarbinol and diacetyl from lactobacilli that have flourished in the juice prior to high temperature evaporation.(5) Lactobacilli are also contaminants in the meat industry acting as spoilage agents of fresh and canned meat, as well as raw marinated herring and diseased rainbow trout. Additionally, lactobacilli are associated with spoilage of beer and milk products.(4)

In direct contrast to their role as spoilage organisms, lactobacilli also aid in the production of a variety of food, beverage and dairy products. The production of lactic acid and gas, a sugar fermentation reaction performed by LAB, is utilized in the production of sausages, salami, yogurt, cheeses, kefir, acidophilus milk, production of sourdough bread, sauerkraut. Because lactobacilli are sensitive to most antibiotics active against gram-positive organisms, they are often used as a method to detect antibiotics in milk.(1,4,5)

Hardy Diagnostics CRITERION™ Lactobacillus Selective Agar Base is a selective agar for the isolation of lactobacilli. The media contains casein peptone and yeast extract for nutrients. Magnesium, manganese, ferrous sulfate and Tween® 80 are essential for most species of lactobacilli as they stimulate growth. Ammonium citrate, sodium acetate, and glacial acetic acid (to lower pH) are instrumental in the inhibitory nature of the media.(3,4)


Gram weight per liter: 84.0gm/L
Sodium Acetate Hydrate 25.0gm
Dextrose 20.0gm
Pancreatic Digest of Casein 10.0gm
Monopotassium Phosphate 6.0gm
Yeast Extract 5.0gm
Ammonium Citrate 2.0gm
Tween ® 80 1.0gm
Magnesium Sulfate 575.0mg
Manganese Sulfate 120.0mg
Ferrous Sulfate 34.0mg
Agar 15.0gm

Final pH 5.5 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.


Store the sealed bottle(s) containing dehydrated culture medium at 2-8ºC. Dehydrated culture medium is very hygroscopic. Keep lid tightly sealed. Protect dehydrated culture media from moisture and light. The dehydrated culture media should be discarded if it is not homogeneous, moist, and lumpy or if the color has changed from its original light beige.

Store the prepared culture media at 2-8ºC.



1. Suspend 84.0gm of the dehydrated culture media in 1 liter of distilled or deionized water. Stir to mix thoroughly.

2. Add 1.32ml of glacial acetic acid.

3. Heat to boiling and mix to dissolve completely.

4. Sterilize in the autoclave at 121ºC. for 15 minutes.

5. Cool to 45-50ºC.

6. Dispense into sterile petri dishes.


For information on procedures and interpretation of results, consult listed references.



Standard microbiological supplies and equipment such as autoclaves, incinerators, and incubators, etc., are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Lactobacillus acidophilus
ATCC ® 4356
A 24-48hr 35°C CO 2 ** Growth; small colonies
Lactobacillus plantarum
ATCC ® 8014
A 24-48hr 35°C CO 2 ** Growth; small colonies
Proteus hauseri
ATCC ® 13315
A 24-48hr 35°C CO 2 ** Inhibited

** Atmosphere of incubation is enriched with 5-10% CO2.

User Quality Control


CRITERION™ Lactobacillus Selective (LBS) Agar Base powder should appear homogeneous, moist, and lumpy, and light beige in color. The prepared media should appear clear with a slight opalescence, and light to medium amber in color.


1. Doyle, M.P., Beuchat, L.R., and Montville, T.J. 1997. Food Microbiology Fundamentals and Frontiers, 1st ed. ASM Press, Washington, D.C.

2. MacFaddin, J.F. Biochemical Tests for Identification of Medical Bacteria,, Lipincott Williams & Wilkins, Philadelphia, PA.

3. Marshall, R.T. 1993. Standard Methods for the Examination of Dairy Products, 16th ed. American Public Health Association, Washington, D.C.

4. Sneath, P.H.A., Nicholas, M.S., Sharpe, E.M., and Holt, J.G. 1986. Bergey's Manual of Systematic Bacteriology, Vol. II. Williams & Wilkins, Baltimore, MD.

5. Vanderzant, C. and Splittstoesser, D.F. 1992. Compendium of Methods for the Microbiological Examination of Foods, 3rd ed. American Public Health Association Washington, D.C.

ATCC is a registered trademark of the American Type Culture Collection.
Tween is a registered trademark of ICI Americas, Inc.