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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. To determine the presence of Enterobacter in a sample, they are first grown on MacConkey agar to confirm they are lactose fermenting. They are facultative anaerobes with a capsule composed of complex acid polysaccharides that allows them to withstand drying for several months. On carbohydrate-rich media, Klebsiella colonies appear greyish-white in colour with a mucosal outer surface. • Escherichia species normally inhabit the human intestine and those of other warm-blooded animals, and are the most commonly responsible for causing disease in humans. Most E. coli strains are motile and have obtained many of their virulence features from horizontal gene transfer. An easy way to differentiate between different types of coliform bacteria is by using an eosin methylene blue agar plate. This plate is partially inhibitory to Gram (+) bacteria, and will produce a color change in the Gram (-) bacterial colonies based on lactose fermentation abilities. These cases were reported from October 15, 2021 through October 27, 2021 and an investigation was carried out by the Minnesota Department of Agriculture and FDA. These were reported between December 2021 and January 2022, and the Public Health Agency of Canada (PHAC), the Canadian Food Inspection Agency (CFIA), and Health Canada were able to determine a specific brand of Original Kimchi to be the source of the organism. The amplification of the beta-D glucuronidase is used to detect E. coli, or the amplification of their verotoxin gene(s) to detect verotoxin-producing E. coli. Chemiluminescent in-situ hybridization Specific areas of the 16S rRNA in the Enterobacteriaceae genus are bound by oligonucleotide probes, which aids in monitoring the quality of drinking water. Violet red bile agar The solid medium is used to grow lactose-fermenting coliforms and utilizes a neutral red pH indicator. Pink colonies appear when lactose is fermented and are surrounded by bile that has precipitated out. To confirm if these colonies are coliforms, they are transferred to brilliant green lactose bile (BGLB) and incubated. If gas is visible after incubation, it can be confirmed that the sample had coliforms present. Membrane filter method Test samples are filtered through standard filter paper and then transferred to M-endo or LES Endo Agar mediums. Colonies appear pinkish-red with green metallic sheen after 22–24 hours of incubation. These colonies can be confirmed as coliforms if they are inoculated in lauryl tryptose (LST), produce gas, and then inoculated in BGLB. If there is gas production in the BGLB tubes, the test is positive for the presence of coliform bacteria. == See also ==
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