McFeters, Cameron and LeChevallier modified Tergitol 7 Agar to improve its selective and differential properties for the recovery of stressed coliforms from chlorinated water (1). They have reported that the selective media such as M-Endo Agars used to isolate gram-negative bacteria recovered only 30% or less as compared to recovery between 71 & 100% of injured coliforms on Tergitol 7 Agar (2). In their study of water samples, including samples containing laboratory-stressed coliforms and surface and drinking water samples, M-Tergitol 7 Agar Base recovered 43% more coliforms than on M-Endo Agar and 36% more coliforms than by using M-Endo Agar with a resuscitation technique (1).
McFeters et al. have also reported recovery of 3.1 times more fecal coliform coliforms on M-Tergitol 7 Agar Base than the standard M-FC method and 1.7 times more than the two-layer enrichment temperature acclimation procedure (3). In another study of 102 drinking water samples 8 to 38 fold more yield of coliforms has been reported on M-Tergitol 7 Agar Base as compared to M-Endo Agar LES (4).
The casein enzymic hydrolysate and peptic digest of animal tissue provide necessary nitrogenous growth factors. Yeast extract is the source of B-vitamins and organic nitrogen and carbon compounds. Lactose is the fermentable carbohydrate. Microorganism fermenting lactose produces yellow colonies due to reaction with bromothymol blue and bromocresol purple indicators. These indicators also act as inhibitors of non-coliform microbes.
Sodium heptadecyl sulphate (Tergitol 7) and polyoxyethylene ether W-1 are surface active agents which inhibit growth of gram-positive bacteria as well as swarming of Proteus (1,5). Inhibition of gram-positive bacteria can be improved by aseptically adding penicillin G (1.0 µg/ml) after autoclaving and cooling to 45°C.
Storage and Shelf-life:
Store below 30°C in tightly closed container and the prepared medium at 2 8°C. Use before expiry date on the label.
References:
1. McFeters, LeChevallier and Cameron 1983, Appl. Environ. Microbiol. 45:484.
2. McFeters, Cameron and LeChevallier 1982 Appl. Environ. Microbiol., 43:97.
3. LeChevallier, Jakanoski, Camper and McFeters 1984 Appl. Environ. Microbiol. 48:371.
4. McFeters, Kippin and LeChevallier 1986, Appl. Environ. Microbiol., 51:1.
5. Pollard, 1946 Science, 103:758.