Coliform

Overview of coliform bacteria and their significance in microbiology and public health

Coliform bacteria are a broad class of bacteria found in the environment, including the feces of humans and other warm-blooded animals. They are defined as rod-shaped, Gram-negative, non-spore forming bacteria that can ferment lactose with the production of acid and gas when incubated at 35-37°C. Coliforms are often used as indicator organisms to assess the sanitary quality of foods and water.

Characteristics

Coliform bacteria are part of the family Enterobacteriaceae, which includes many genera such as Escherichia, Klebsiella, Enterobacter, and Citrobacter. These bacteria are typically motile, facultative anaerobes that can grow in a variety of environments. They are characterized by their ability to ferment lactose to produce acid and gas within 48 hours at 35°C.

Types of Coliforms

Coliforms are generally divided into two groups:

• Total coliforms: This group includes all coliform bacteria, which are found in the environment and feces of all warm-blooded animals. They are not necessarily harmful but indicate the potential presence of pathogenic organisms.

• Fecal coliforms: A subset of total coliforms, fecal coliforms are more specifically associated with fecal contamination. The most well-known fecal coliform is Escherichia coli (E. coli), which is used as a specific indicator of fecal pollution and the presence of enteric pathogens.

Significance in Public Health

Coliform bacteria are used as indicator organisms to evaluate the microbiological quality of water and food. The presence of coliforms in drinking water suggests that there may be a pathway for pathogens to enter the water supply, posing a risk to human health. Regulatory agencies, such as the United States Environmental Protection Agency (EPA), have established standards for coliform levels in drinking water to ensure safety.

Detection and Testing

Several methods are used to detect coliform bacteria in water and food samples, including:

• Multiple-tube fermentation technique: This traditional method involves inoculating a series of tubes with the sample and observing gas production.

• Membrane filtration: A sample is filtered through a membrane that retains bacteria, which are then cultured on selective media.

• Enzyme substrate tests: These rapid tests use substrates that change color or fluoresce in the presence of coliforms.

Prevention and Control

To prevent coliform contamination, it is essential to maintain proper sanitation and hygiene practices, such as treating drinking water, ensuring proper sewage disposal, and following food safety guidelines.

Also see

• Escherichia coli
• Water quality
• Microbial contamination
• Food safety