HiCrome™ Staph Agar Plate, Modified

Principle And Interpretation

Staphylococci are widespread in nature, though they are mainly found living on the skin, skin glands and mucous membranes of mammals and birds. Humans and animals are the primary source of this organism. Because of its widespread nature it is easily transferred to food and a cause of food poisoning if not handled properly (1). The coagulase positive species S. aureus is well documented as a human opportunistic pathogen. Staphylococcus species are a major cause of food poisoning and produces a wide variety of enterotoxins, thus causing various types of disease symptoms. The ability to clot plasma continues to be the most widely used and accepted criterion for the identification of pathogenic staphylococci associated with acute infections (2).

This medium is a selective chromogenic medium recommended for the isolation and enumeration of coagulase positive staphylococci in foods within 24 hours. This medium has an advantage over the traditional media which requires 48 hours Peptones in the medium supplies the essential nitrogneous compounds required for the growth. The chromogenic mixture incorporated in the medium is specifically cleaved by Staphylococcus aureus to give bluish green coloured colonies which are clearly visible against the opaque background. Sodium pyruvate enhances the growth of Staphylococcus species. Sodium chloride in the medium helps to maintain the osmotic equilibrium of the medium. High concentration of sodium chloride also helps in inhibiting the accompanying microflora. Lithium chloride inhibits most of the contaminating microflora. Addition of PolyB Selective Supplement (FD003) helps to restrict growth of gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa.