Xylose Lysine Deoxycholate (XLD) Agar is a selective and differential medium used to isolate enteric pathogens — especially Salmonella and Shigella — from stool cultures. Let’s decode what you see on the plate 👇 #Salmonella Ferments xylose → turns yellow at first Then decarboxylates lysine → reverts to red Produces H₂S → black centers 👉 Result: Red colonies with black centers #Shigella Doesn’t ferment xylose No H₂S production 👉 Result: Red colonies without black centers #Ecoli (or other colif