Lauryl Sulphate Tryptose Broth Modified (mlST)

The pathogenicity of Cronobacter sakazakii for unweaned babies makes it necessary to review the manufacturing process of the products intended for babies, guaranteeing the absence of the bacteria in the final product. Additional prevention measures at hospitals include the sanitary hygiene of the prepared media, reducing the time between the preparation and its administration, to impede the multiplication of microorganisms.

Enzymatic digest of plants and animal tissue provides nitrogen, vitamins, minerals and amino acids essential for growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Potassium phosphates act as a buffer system. Lactose is the fermentable carbohydrate providing carbon and energy. Sodium lauryl sulfate is the selective agent, inhibiting many organisms except coliforms.

The ISO 22964 standard recommended this medium as a selective enrichment with the addition of vancomycin and incubation at 44 °C. All the tubes must be subcultured in the chromogenic agar for the isolation of Cronobacter sakazakii ESIA (LC-1446).

Preparation

Suspend 32.3 grams of the medium in 500 mL of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Autoclave at 121 °C for 15 minutes. Cool to 45-50 °C and aseptically add 1 vial of Vancomycin Supplement (LC-6072). Homogenize gently and dispense into tubes in amounts of 10 mL.

Instructions for use

Inoculation method:

1. Take the inoculum with a sterile loop.
2. Submerge the loop into the medium and shake gently.
3. Incubate at 44 ± 0.5 °C and observe after 24 ± 2 hours.

• ISO/TS 22964 Milk and milk products - Detection of Enterobacter sakazakii.
• GUILLAUME-Gentil, O., Sonnard, V. Kandahai, M.C., Mauragg, J.D. and Jootsen, H. A simple and Rapid Cultural Method for Detection of Enterobacter sakazakii in environmental samples. Journal of Food Protection, 68 (1), 2005, pp. 64-69.