Microbiological Fact Sheet
Total Coliform in Drinking Water (Enzyme Substrate Presence/Absence)
|Method Summary||A commercially prepared, pre-weighed enzymatic medium is added to 100 mL of sample and incubated for 24 hours at 35°C. The sample is examined for color change and fluorescence to determine the presence of total coliform bacteria and E.coli.
Chromogenic substrates are used to detect the enzyme β-D-galactosidase, which is produced by total coliform bacteria. The β-D-galactosidase enzyme hydrolyzes the substrate and produces a color change, which indicates a positive test for total coliforms at 24 hours without additional procedures. A fluorogenic substrate is used to detect the enzyme β-glucuronidase, which is produced by E.coli. The β-glucuronidase enzyme hydrolyzes the substrate and produces a fluorescent product when viewed under long-wavelength ultraviolet light. The presence of fluorescence indicates a positive test for E.coli. The enzyme substrate coliform test is recommended for the analysis of drinking and source water samples.
Link to the National Library of Medicine's Toxicology
Database for more references
on this analyte.
|Escherichia coli Organism||This bacterium is a natural inhabitant only of the intestinal tract of many animals, particularly warm-blooded mammals. Its presence in water samples is an indication of fecal pollution and the possible presence of enteric pathogens. Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present. The E. coli test is used as a measure of drinking and recreational water quality. Due to the risk of gastrointestinal illness indicated by E. coli presence, all drinking water must test negative for this bacterium. Total coliforms are a group including E. coli which encompasses a broader spectrum of gastrointestinal bacteria.
|Result Interpretation||“A” – The test is negative for both total coliforms and E. coli. ||“P (A)” – The test is positive for total coliforms and negative for E. coli. ||“P (P)” – The test is positive for total coliforms and E. coli.
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