Escherichia coli on MacConkey agar. There are many variations of MacConkey agar depending on the need (here MacConkey Agar No.1, Oxoid®). In comparison with MacConkey No.3 is this medium less selective and enables growth of some Gram-positive bacteria (e.g., staphylococci, enterococci).. In the picture you can see red lactose-positive colonies of E.coli and white lactose-negative colonies of Salmonella enterica.

Cultivation 24 hours, 37°C in an aerobic atmosphere.