Lauryl tryptose broth

Lauryl tryptose broth (LTB) is a selective growth medium (broth) for coliforms.^[1]

Lauryl tryptose broth is used for the most probable number test of coliforms in waters, effluent or sewage. It tests for lactose fermentation with gas production. Sodium lauryl sulfate inhibits organisms other than coliforms.

Formula in grams/litre (g/l)

: 20.0,

Lactose : 5.0,

Sodium chloride : 5.0,

Dipotassium phosphate : 2.75,

Potassium dihydrogen phosphate : 2.75,

Sodium dodecyl sulfate : 0.1

pH 6.8 ± 0.2

Samples positive for gas production are transferred to (BLGB) to detect the ability to grow in the presence of bile and produce gas at 95 °F (35 °C) for 48 hours. The absence of gas production in 48 hours is considered a negative test for coliforms.^[2] Gas production serves as both a presumptive test and a confirmatory medium.

Fecal coliforms are distinguished from coliforms by growth in at 113.9 °F (45.5 °C) for 24 hours.

References[]

^ Mallmann, W. L.; Darby, C. W. (February 1941). "Uses of a Lauryl Sulfate Tryptose Broth for the Detection of Coliform Organisms". Am J Public Health Nations Health. 31 (2): 127–134. doi:10.2105/ajph.31.2.127. PMC 1531262. PMID 18015383.
^ Anne Maczulak (2011), "most probable number", Encyclopedia of Microbiology, pp. 542–545

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[1] Mallmann, W. L.; Darby, C. W. (February 1941). "Uses of a Lauryl Sulfate Tryptose Broth for the Detection of Coliform Organisms". Am J Public Health Nations Health. 31 (2): 127–134. doi:10.2105/ajph.31.2.127. PMC 1531262. PMID 18015383.

[2] Anne Maczulak (2011), "most probable number", Encyclopedia of Microbiology, pp. 542–545

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