Methode zum direkten nachweis von Escherichia coli in wasser

A rapid membrane filter method employing ECD agar for the direct enumeration of Escherichia coli type 1 in water is described. After a preincubation period of 4 h at 37 °C on trypticase soy agar the membrane is transferred to ECD agar for an additional 12–24 h incubation at 44 °C. E. coli colonies are identified by a positive indole test performed directly on the membrane.

E. coli colonies are easily recognized within a few minutes by their red color and a red halo surrounding the colony. The positively evaluated colonies from natural samples were confirmed to indeed be comprised of E. coli to an extent of 98%.

No difference in E. coli recovery from natural samples was obtained by these means when compared with tests utilizing either M-FC medium or tergitol 7 agar. Regarding specificity, however, the described method was found to be superior to both the M-FC and the tergitol 7 procedures.