LPT Dilution Broth

Tryptone 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. Lecithin and Tween 80 neutralize quaternary ammonium compounds and inhibit the action of the preservatives. Antimicrobial preservatives are commonly used in cosmetic products in order to reduce their microbial contamination. Cosmetics, due to their nature, are sensitive to microbial contamination and should be preserved, as they are used in eyes, damaged skin or for long periods of time.

Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.

Preparation

Suspend 29 grams of the medium in one liter of distilled water. Mix well and add 30 mL of Tween 80. Dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Dispense into appropriate containers and sterilize in autoclave at 121 °C for 15 minutes.

Instructions for use

For the homogenization and dilution of samples:

1. Homogenize the sample using a 1 in 10 dilution. If necessary, use this suspension to prepare further decimal dilutions.
2. Leave the tubes at room temperature for a time sufficient to allow the neutralizing agents to inhibit the activity of preservatives contained in cosmetic products, but not sufficient to encourage multiplication of the organisms.
3. Inoculate a solid medium to enumerate the contaminating microorganisms.

For the enrichment of microorganisms in cosmetic products:

1. Inoculate the sample in the LPT Dilution Broth and incubate at 35 ± 2 °C for 18-24 hours.

• Microbiologia nell'Industria Cosmetica. UNIPRO, aprile 1990, vol. 1. Ricerche e Tecnologie Cosmetiche.