This HiDip slide is recommended for microbial screening of food and water. PCA: Plate Count Agar : Recommended for determination of plate counts of microorganisms in food, water, waste water & clinical . Also called as Standard Methods Agar. It is recommended by APHA and FDA for determination of counts. Red coloured indicates growth. Cetrimide Agar- A selective medium for Pseudomonas where cetrimide acts as the inhibitory agent.