Scharlab have added Columbia CNA Agar to their catalogue of culture media. Widely used medium in the clinical laboratory for the selective isolation of Gram-positive cocci with the addition of defibrinated blood to the formulation.

This medium owes its selectivity to the presence of two antibiotics: nalidixic acid and colistin. The advantage which this Scharlau medium offers regular users is that these antibiotics are already incorporated in its formulation, and there are no further additions necessary in the form of supplements.

Nalidixic acid inhibits Enterobacteriaceae in particular, whereas Pseudomonas is especially susceptible to colistin. The combination of these antibiotics is very effective in allowing the growth and haemolytic reactions of Staphylococci, Streptococci, Enterococci and yeasts.