Coliform bacteria

Coliform bacteria are defined as either motile or non-motile Gram-negative non-spore forming bacilli that possess β-galactosidase to produce acids and gases under their optimal growth temperature of 35–37 °C. They can be aerobes or facultative aerobes, and are a commonly used indicator of low sanitary quality of foods, milk, and water. Coliforms can be found in the aquatic environment, in soil and on vegetation; they are universally present in large numbers in the feces of warm-blooded animals as they are known to inhabit the gastrointestinal system. While coliform bacteria are not normally the cause of serious illness, they are easy to culture, and their presence is used to infer that other pathogenic organisms of fecal origin may be present in a sample, or that said sample is not safe to consume. Such pathogens include disease-causing bacteria, viruses, or protozoa and many multicellular parasites.

Every drinking water source must be tested for the presence of these total coliform bacteria.

General

Typical genera include:

Citrobacter are peritrichous facultative anaerobic bacilli between 0.6–6 μm in length. Citrobacter species inhabit intestinal flora without causing harm, but can lead to urinary tract infections, bacteremia, brain abscesses, pneumonia, intra abdominal sepsis, meningitis, and joint infections if they are given the opportunity. Infections of a Citrobacter species has a mortality rate between 33–48%, with infants and immunocompromised individuals being more susceptible.

Enterobacter are motile, flagellated bacilli known for causing infections such as bacteremia, respiratory tract infections, urinary tract infections, infections of areas where surgery occurred, and in extreme cases meningitis, sinusitis and osteomyelitis. To determine the presence of Enterobacter in a sample, they are first grown on MacConkey agar to confirm they are lactose fermenting.