Fecal coliform
Indicator of potential fecal contamination in water.
Fecal coliform (also known as thermotolerant coliform) is a facultatively anaerobic, rod-shaped, Gram-negative, non-sporulating bacterium. It is notable as an indicator of potential fecal contamination in water, though its presence does not necessarily indicate direct harm or the presence of feces. The term 'thermotolerant coliform' is considered more correct and is gaining acceptance.
- Incubation temperature
- 44 ± 0.5°C
- Incubation time
- 48 hours
- Typical sample volume
- 100 ml
- Desired colony density range
- 20 to 60 colonies per filter
- Membrane filter pore size
- 0.45 micrometre
- Incubation temperature for m fc agar
- 44.5 °C (112.1 degrees F)
- Incubation time for m fc agar
- 24 hours
Lore & Background
Fecal coliform bacteria generally originate in the intestines of warm-blooded animals. They are capable of growth in the presence of bile salts or similar surface agents, are oxidase negative, and produce acid and gas from lactose within 48 hours at 44 ± 0.5°C. Coliform bacteria include genera that originate in feces, such as Escherichia, Enterobacter, Klebsiella, and Citrobacter. The fecal coliform assay is intended to be an indicator of fecal contamination, more specifically of E. coli, which is an indicator microorganism for other pathogens that may be present in feces. However, the presence of fecal coliforms in water may not be directly harmful and does not necessarily indicate the presence of feces. Their presence may also result from plant material or pulp and paper mill effluent.
Reader's Guide
Fecal coliform testing is a key component of water quality monitoring in the U.S., Canada, and other countries. In the U.S., it is one of nine tests used by the EPA to form an overall water-quality rating. The presence of fecal coliforms can warn of failure in water treatment, a break in distribution system integrity, or possible contamination with pathogens. High levels may indicate an elevated risk of waterborne gastroenteritis. Sources include failing septic systems, combined sewer overflows, agricultural runoff, and livestock near water bodies. While large quantities are not directly harmful according to some authorities, they may indicate a higher risk of pathogens such as those causing dysentery, typhoid fever, and hepatitis A. Treatment methods include boiling, chlorine, UV disinfection, and iodine. The EPA's Total Coliform Rule, published in 1989, imposed major monitoring changes for public water systems, increasing routine coliform tests and requiring triggered source water monitoring. The rule was revised in 2013 with minor corrections in 2014.
Did You Know?
- The term 'thermotolerant coliform' is gaining acceptance over 'fecal coliform'.
- Membrane filtration with a 0.45 micrometre filter is the method of choice for analysis.
- Newer methods use enzyme substrates that allow detection of E. coli and coliforms in the same pot.
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