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Desoxycholate Citrate Agar (DCA) (Hynes) One of several media designed for the differential selective isolation of Salmonella and Shigella spp from clinical and environmental samples. Lactose is added to the medium together with Neutral Red indicator to assist in the differentiation of Lactose and Non-Lactose fermenting organisms. The medium is made selective by the inclusion of Sodium Desoxycholate and Sodium Thiosulphate, which will inhibit most gram-positive organisms. The Sodium Thiosulphate is also broken down by the enzyme thiosulphate reductase to form Sodium Sulphite and Hydrogen Sulphide. The Hydrogen Sulphide, if present, will in turn react with the ferric ions to produce a black precipitate of Ferrous Sulphide and give rise to the classical black centre of most Salmonellae. It has been suggested that this medium may be more suitable for secondary post-enrichment isolation while the original formulation is more appropriate for the primary inoculation of samples. -
A selective medium for the isolation of Staphylococcus aureus. The high level of Sodium Chloride inhibits most other organisms and as most Staphylococcus aureus ferment Mannitol the inclusion of Phenol Red indicator gives rise to yellow colonies. This formulation complies with the requirements of the Harmonised USP/EP/JP. NB: Some strains of coagulase negative staphylococci can give rise to false positive results on this medium It is necessary therefore to confirm the identity of Staphylococcus aureus by other confirmatory tests (e.g. Coagulase test, Latex test etc.) -
This is an aqueous solution of Sodium Hydroxide (2%) with Phenol Red Indicator suitable for use in the digestion of Sputum samples prior to culture of the samples for Mycobacterium spp. It is generally used in conjunction with Sputum Neutralising Buffer (BM1324).
