Isolation of Serratia marcescens on deoxyribonuclease-toluidine blue-cephalothin agar

Serratia marcescens was isolated on a new medium-commercial deoxyribonuclease agar with the addition of cephalothin (1,000 mug/ml) and Toluidine Blue (1,000 mug/ml). It was detected in water samples even though it comprised only 0.1 to 0.0001% of the total bacterial population.