Question
Eijkman test
Answer
The Eijkman test is a specific bacteriological test used to detect faecal coliforms (as opposed to total/environmental coliforms) in water, providing a more specific indicator of recent faecal contamination than the general presumptive coliform test.
Principle: faecal coliforms (predominantly Escherichia coli, of intestinal/faecal origin) are distinguished from non-faecal (environmental) coliform organisms by their ability to ferment lactose with acid and gas production at an elevated incubation temperature of 44–44.5°C — a temperature at which most non-faecal environmental coliforms fail to grow/ferment lactose, while true faecal coliforms, adapted to the warm intestinal environment, continue to do so.
Procedure: water sample (or subculture from a positive presumptive coliform tube) is inoculated into a lactose-containing broth medium (e.g., MacConkey broth or Eijkman’s/EC broth) with a Durham’s tube to trap gas, and incubated at the elevated temperature (44–44.5°C, in a specialized water bath) for 24–48 hours.
Interpretation: production of acid and gas at this elevated temperature is a positive Eijkman test, confirming the presence of faecal coliforms and thereby providing strong, specific evidence of faecal contamination of the water source — distinguishing genuine sewage/faecal pollution from a positive standard (37°C) presumptive coliform result that could theoretically arise from non-faecal environmental coliform organisms.
Clinical/public health significance: an important confirmatory step in the standard sequence of water potability testing (presumptive → confirmed → completed tests), providing more specific evidence linking a positive coliform result to genuine faecal/sewage contamination, and thereby to a genuine risk of enteric pathogen presence, rather than a false alarm from harmless environmental coliform bacteria.