High quality products for microbiological applications
There are a group of Bile Salts used as agents in microbiological agars. These include NZP’s Bile Salts No. 3, Special Bile (a natural mixture of the conjugated bile acid salts), sodium deoxycholate, sodium cholate, sodium taurodeoxycholate and sodium taurocholate.
Sodium cholate and sodium deoxycholate are the sodium salts of cholic acid and deoxycholic acid.
Bile Salts No. 3 is a mixture of the two salts, sodium cholate and sodium deoxycholate, which was developed specifically for microbiological applications.
Special Bile is a refined bile product containing a mixture of the natural conjugated bile acids and is used as a selective inhibitory agent in microbiological media. It differs from Ox Bile Extract in several ways, in particular it is a purer mixture of the conjugated bile acids. It contains very little of the normal non-bile acid fraction found in Ox Bile Powder. Special Bile is preferred for media such as MacConkey broth and agar, Brilliant Green Bile Broth and EE Broth.
Features of Special Bile
Special Bile is often the preferred bile product for media applications, such as MacConkey broth and agar, Brilliant Green Bile broth and agar and EE Broth. The world's leading brands choose NZP's Special Bile to be the bile component in their MacConkey agar and broth formulations.
The bile used for Special Bile is carefully selected to contain a very low level (<0.5% w/w) of free deoxycholic acid. Bile powders with high levels of deoxycholic acid demonstrate a toxicity that may be unacceptable for use in, for example, MacConkey media and EE Broth. For this reason special bile is often considered to be a better choice in MacConkey agars than ox bile powder or bacteriological bile.
The colour of special bile is carefully controlled in order to provide media suppliers with a consistent product for use in media such as MacConkey agars and broths and Brilliant Green Bile broths, by being light enough in colour for effective and consistent dye coloration. Unlike crude bile powders, the product will not form a surface scum or a deposit in culture media.
Bacteriological Performance of Special Bile
MacConkey Broth and Agar made with Special Bile at the Minimum Effective Concentration supports satisfactory growth of bile tolerant organisms, including pathogenic staphylococci. Gas production by clostridia is inhibited in broths containing higher concentrations of Special Bile (eg. Brilliant Green Bile Broth), therefore eliminating false positives for E.coli.
These are just a couple of examples of the advantages seen by culture media manufacturers for the use of NZP's Special Bile in their selective media.
Bile Salts Applications
In nature, the liver converts cholesterol into the conjugated salts of glycocholic and taurocholic acid, which are excreted into the bile. Bile is released into the intestine where the bile salts emulsify fats and promote digestion, enabling lipid products to migrate through the gut wall by way of the hepatic portal circulation and into the liver for metabolic processing. About 90% of the bile salts are reabsorbed by the intestine and pass back to the liver by a process referred to as enterohepatic circulation.
NZP Bile Salts are used in microbiological culture media. Their application is selective for the isolation of gram-negative bacteria while inhibiting the growth of Gram-positive bacteria. A major use is in clinical microbiology to selectively grow faecal staphylococci and streptococci. It is not a simple choice to select which bile salt is best for a specific application but most supply companies have simplified the task by offering blends of agar media with their specific recommendations for the application. It is common to utilise the bile salts in their various proportions in selective media for the detection and quantification of coliform organisms in water, food and dairy products as well as in healthcare applications.
NZP offers samples for researchers and companies to enable them to efficiently determine the best bile salt or mixture of bile salts for the application in review.