Cultivation of Serratia marcescens on differential media. A, Serratia marcescens on chrome agar colonies appeared pink with a dark center at 30 °C. B, on chrome agar colonies, appeared blue to purple at 37 °C. C, on MacConkey agar colonies, appeared red and exhibited lactose fermentation. D, on nutrient agar colonies at 30 °C, appeared red like blood.