koliformid

Koliformid, also known as coliforms, are a broad group of Gram-negative, non-spore-forming, facultatively anaerobic rods within the family Enterobacteriaceae. They are primarily used as indicators of fecal contamination in water and, to a lesser extent, in foods.

Defining features and ecology: Coliforms ferment lactose with acid and gas production within about 24 hours at 35–37°C. They are commonly found in the intestinal tract of warm-blooded animals but can also occur in the environment, including soil and vegetation. A subset called fecal coliforms, which includes Escherichia coli, is more specifically associated with fecal material. Some testing approaches distinguish fecal coliforms by their ability to grow at higher temperatures, such as 44.5°C.

Public health relevance: The presence of coliforms in water signals possible fecal contamination and the potential presence of enteric pathogens, including viruses, bacteria, and protozoa. As such, coliform tests are widely used in drinking-water quality and recreational-water monitoring to assess safety and the need for further investigation or treatment. Standards typically report counts as total coliforms, fecal coliforms, or Escherichia coli, guiding regulatory decisions.

Methods and interpretation: Common laboratory methods include membrane filtration and most probable number (MPN) techniques using lactose-based media. Results are interpreted in the context of local standards, which often require zero or very low coliform counts in treated drinking water. However, coliform presence does not guarantee illness and some pathogens may be absent even when coliforms are detected.

Limitations: Not all coliforms originate from fecal sources, and not all fecal pathogens are associated with coliforms. Consequently, coliform testing is used as an indicator alongside other assessments rather than as a definitive measure of safety.