Tergitol-7 TTC Medium (without Membrane Filter)

Principle And Interpretation

Field of Application: Water (ISO 9308-1, 2001). DriFilter Membrane Nutrient Pad Medium is ready to use sterile culture media in the form of a 50 mm biological inert absorbent pads impregnated with Tergitol-7 medium, then dried and sterilized in 55 mm petri plate. They eliminate the need of laborious media preparation and autoclaving procedures. The nutrient pads are to be just rewetted with sterile distilled water and are ready to use. Use of nutrient pads allows larger sample volumes to be tested at a time. Interpretation of results is directly by counting the CFUs and also quantifies the microbial load present in the sample. Tergitol-7 Broth was originally designed by Chapman (1) and later on modified by incorporating 2,3,5-Triphenyl Tetrazolium Chloride (TTC) into the medium. This medium is selective and differential which is used for the detection and enumeration of coliform organisms. Pollard (2) has reported the selective bactericidal property of sodium heptadecyl sulphate (Tergitol-7). Kulp et al (3) corroborated the use of Tergitol-7 medium with TTC in routine analysis of water and Mossel (4) used this medium for the examination of food materials. Sodium heptadecyl sulphate (Tergitol-7) inhibits gram-positive bacteria and Proteus swarming and yields better recovery of coliforms. Bromo thymol blue is the pH indicator. Lactose fermenting organisms form yellow coloured medium while Klebsiella and Enterobacter form greenish yellow coloured medium. Lactose non-fermenters produce blue coloured medium. TTC is reduced in the bacterial cell to form formazan, a red coloured insoluble complex thereby producing red coloured medium.