The IMViC test has two drawbacks. The first, It has many controversial procedures and second is test results do not give satisfactory differentiation between fecal and non-fecal coliforms. In 1904 Eijkman proposed another test to differentiate fecal and non-fecal coliform.
Principle of Eijkman Test
- Only fecal coliforms of warm blooded animals grow at 46°C and ferment lactose with Acid & Gas production
- Most strains of fecal E.coli can ferment lactose in a special buffered broth when incubated at 45°C, where as very few or less frequently the Enterobacter aerogenes do so.
- The test is called as Eijkman test or elevated temperature test.
Procedure of Eijkman Test
- A buffered tryptose lactose broth in tubes with inverted Durham's tube is inoculated with a culture of coliforms.
- It is then incubated in water jacketed incubator at 45°C for 48 hours.
- Gas production after incubation constitutes a positive test for fecal coliforms.
- Another method, instead of tryptone lactose broth, buffered boric acid lactose broth (BALB) medium is used.
- The advantage is that, the medium used is selective for fecal Escherichia.
- It selectively inhibits growth and gas production by Enterobacter and other intermediate members of coliforms.
- Sterile medium is first warmed to 37°C and then inoculated with culture & incubated at 45°C for 48 hrs.
- Gas production indicates positive test.
- Eijkman test gives better result than IMViC tests.
- Therefore, it is generally preferred in water examination.
