Written and maintained by CASRAI Editorial Board
Last updated
General information, not medical or water-treatment advice for any individual household.
Short answer
Fecal coliforms are gram-negative, non-spore-forming rods found in the intestines and feces of humans and other warm-blooded animals; the predominant one can be E. coli. They are used as an indicator that fecal contamination, and therefore other pathogens, may be present (EPA Method 1680, sections 1.1 and 3.1). The group is defined by a laboratory method, not by a taxonomic rank, which is why results depend on the test used.
Definition and scope
EPA Method 1680 (EPA-821-R-14-009, September 2014) gives an operational definition: in that method, fecal coliforms are the bacteria that grow and produce gas in lauryl tryptose broth (LTB) within a total of 48 ± 3 hours at 35 ± 0.5 °C, and that then ferment lactose and produce gas within 24 ± 2 hours in EC broth at 44.5 ± 0.2 °C. The method notes that coliforms from other sources often cannot produce gas under these conditions, so the elevated-temperature step is what defines the fecal component of the coliform group.
Searches such as bacteria fecal and fecal bacteria usually mean this indicator group, but they can also mean any bacteria of fecal origin. Fecal coliform is one indicator, not a list of every bacterium in feces.
How fecal coliform testing works in practice
Method 1680 is a most probable number (MPN) multiple-tube procedure for fecal coliforms in biosolids. LTB serves as the presumptive medium and EC as confirmation. EC may not be used for direct isolation from a sample, because prior enrichment in LTB is required for optimum recovery. Results are reported as MPN per gram of total solids (dry weight). Class A biosolids are defined as below 1,000 MPN/g, and Class B as a geometric mean below 2 × 106 MPN/g (sections 2.2, 3.2 and 3.3).
Holding time is part of the result
For sewage sludge (biosolids) only, Method 1680 extends the holding time to 24 hours for Class A composted, Class B aerobically digested and Class B anaerobically digested samples. All other matrices should be analysed within 8 hours of collection, with a 6-hour maximum transport time and 2 hours for sample processing. The method states that results are considered invalid if these conditions are not met (section 8.11). For lab staff, collection-to-analysis timing is therefore a pre-analytical control, not a convenience. Transport media used for other microbiology work are covered in Transport Medium in Microbiology; they are a different tool from the time limits above.
How can I test for fecal coliform in water?
For drinking water, EPA advises using only laboratories certified to do drinking water testing, and points people to their state certified laboratory or local health department, which may provide private well testing (EPA, Protect Your Home’s Water, read 2026-11-07). Method 1680 is a biosolids method; it is not a home test procedure. For lab-side context on selective and differential media used in enteric microbiology, see MacConkey agar. Sampling equipment for regulatory wastewater monitoring is covered in the wastewater autosampler guide.
Total coliform vs fecal coliform vs E. coli
These terms are related but are not interchangeable. The table is built only from the EPA sources listed below.
| Indicator | What the source says | Source |
|---|---|---|
| Total coliforms | A group of related bacteria that are, with few exceptions, not harmful to humans; EPA considers them a useful indicator of other pathogens for drinking water, used to judge treatment adequacy and distribution-system integrity. | EPA, Revised Total Coliform Rule page |
| Fecal coliforms | Method-defined subgroup (growth and gas at 44.5 °C in EC after LTB); the predominant member can be E. coli. | EPA Method 1680, section 3.1 |
| E. coli | The Revised Total Coliform Rule sets a maximum contaminant level goal (MCLG) and maximum contaminant level (MCL) for E. coli for protection against potential fecal contamination. | EPA, Revised Total Coliform Rule page |
| Enterococci and E. coli (recreational water) | Culturable enterococci and E. coli are described as better indicators of fecal contamination than total coliforms and fecal coliforms. | EPA, Recreational Water Quality Criteria (2012) |
Where it matters for labs and water-quality programs
Fecal coliform was once the recreational-water indicator. The U.S. Public Health Service recommended it in the 1960s, and EPA recommended a criterion of 200 fecal coliform cfu per 100 mL in 1976. After epidemiological studies in the late 1970s and early 1980s, EPA’s 1986 criteria recommended enterococci for marine and fresh waters and E. coli for fresh waters (a geometric mean of 126 E. coli cfu per 100 mL), replacing the fecal coliform recommendation. Fecal coliform remains in use where a method names it, such as the biosolids classes above. A lab should therefore read the method named in its permit or protocol rather than assume which indicator applies.
What are examples of fecal coliforms?
The organism EPA Method 1680 names is E. coli, as the predominant fecal coliform. Because the group is defined by growth and gas production under stated conditions, other bacteria that meet those criteria would be counted too.
Common misunderstandings
- “Fecal coliform” and “E. coli” are the same thing. E. coli is the predominant fecal coliform, but fecal coliform is a method-defined group.
- Any coliform means feces. Total coliforms are a broader group that EPA describes as, with few exceptions, not harmful; they are used as an indicator.
- Results can be compared across methods without checking. Units (MPN per gram dry weight, cfu per 100 mL) and holding-time rules differ by method and matrix.
FAQ
What does it mean if there is moderate growth of coliform bacteria?
A growth description on its own has no fixed meaning in the sources used for this page. Interpretation depends on the sample type, the method, the units reported and the applicable standard, so take the result to the certified laboratory or local health department that issued it.
What happens if I drink water with coliform?
EPA states that total coliforms are with few exceptions not harmful themselves but are used as an indicator that pathogens may be present, and it lists recurring gastro-intestinal illness among the reasons to test well water for coliform bacteria. For a specific result or symptoms, contact your local health department or a clinician; this page cannot advise individuals. If a private well exceeds health standards, EPA advises contacting the public health department for specific steps and re-testing to confirm.
How can I test for fecal coliform in water?
Use a laboratory certified for drinking water testing; see the section above.
Sources
- U.S. EPA, Method 1680: Fecal Coliforms in Sewage Sludge (Biosolids) by Multiple-Tube Fermentation Using LTB and EC Medium, EPA-821-R-14-009, September 2014. epa.gov (read 2026-11-07).
- U.S. EPA, Recreational Water Quality Criteria (2012). epa.gov (read 2026-11-07).
- U.S. EPA, Revised Total Coliform Rule and Total Coliform Rule. epa.gov (read 2026-11-07).
- U.S. EPA, Protect Your Home’s Water (private wells). epa.gov (read 2026-11-07).
