Giolitti-Cantoni Broth Base is a selective enrichment medium, widely used for isolating Staphylococcus aureus from foods as recommended by ISO 6888-3:2003. This article focuses on the composition, method, and application of Giolitti-Cantoni Broth Base in microbiological analysis.
Giolitti-Cantoni Broth Base is specifically designed for the enrichment of Staphylococcus aureus from food samples. Composed of tryptone, beef extract, yeast extract, D-mannitol, lithium chloride, sodium chloride, glycine, and sodium pyruvate, this medium has a final pH of 6.9 ± 0.2 at 25°C. The mannitol and lithium chloride in the formulation provide a selective environment conducive to the growth of Staphylococcus aureus while inhibiting other bacteria. It is used in conjunction with a potassium tellurite supplement, enhancing its selectivity. The medium’s effectiveness is recognized by ISO standards, making it a reliable choice for food safety testing.
Composition and Working Principle
The Giolitti-Cantoni Broth Base formula includes 10.0 g/l tryptone, 5.0 g/l beef extract, 5.0 g/l yeast extract, 20.0 g/l D-mannitol, 5.0 g/l lithium chloride, 5.0 g/l sodium chloride, 1.2 g/l glycine, and 3.0 g/l sodium pyruvate. Tryptone, beef, and yeast extracts provide essential nutrients, while mannitol serves as a fermentable carbohydrate. The presence of lithium chloride and glycine enhances the selectivity against competing flora.
Preparation and Application
To prepare the medium, 54.2 g of the powder is suspended in 1 liter of distilled or deionized water, heated gently with shaking until dissolved, and distributed into 19 ml tubes. After autoclaving at 121°C for 15 minutes, the medium is cooled to 45-50°C, and potassium tellurite supplement is added aseptically. The medium is primarily used for enriching Staphylococcus aureus from food samples during isolation procedures.
Testing Procedure and Interpretation
For microbiological testing, 1 g or 1 ml of the test sample, or a suitable decimal dilution series, is inoculated into the medium and overlaid with molten paraffin wax. After incubation at 36 ± 1°C for 40-48 hours, tubes are examined for blackening of the medium, indicating a positive reaction for Staphylococcus aureus. Confirmation of S. aureus is done by subculturing on Baird Parker Agar.
Storage, Shelf Life, and Quality Control
The dehydrated medium should be stored at 10-30°C in a dry environment and used before the expiry date on the label. Prepared tubes are stored at 2-8°C. Quality control checks involve assessing the medium’s performance using strains like Escherichia coli and Staphylococcus aureus.
Giolitti-Cantoni Broth Base is an essential medium for the selective enrichment of Staphylococcus aureus in food microbiological testing. Its specialized composition and compliance with ISO standards make it an invaluable tool in ensuring food safety and public health.