for the detection and enumeration of Enterobacteriaceae WITH NaCl (ISO 21528)
NUTRIENT AGAR is used for less fastidious microorganisms as well as for permanent cultures (general purposes medium). The medium contains Beef extract, Yeast extract and Peptone as sources of nitrogen, vitamins, amino acids and carbon for potential microorganism’s growth. Sodium chloride ensures osmotic balance. Agar is a solidifying agent. Thus, when adding blood, as supplement the blood cells will not rupture. Addition of 10% different biological fluids such as blood, serum and egg yolk makes it suitable for the cultivation of related fastidious organism. For eg., Pseudomonas aeruginosa produces a blue-green pigment, pyocyanin, which diffuses into the medium giving the plate a characteristic colour. For growing specific bacteria culture, spread the bacteria on the plate using sterile swab or inoculating loop. The bacteria will grow and become visible in 24 – 48 hrs. It is generally used in the laboratory to prepare stock cultures of the bacteria.