BIOL 2P98 Lecture Notes - Lecture 23: Fecal Coliform, Pathogenic Escherichia Coli, Indicator Organism

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19 Jan 2016

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Chapter 31: water and food as vehicles of bacterial diseases. Public health and water wuality: potable and recreational water are routinely tested for specific. Testing for fecal coliforms: membrane filter procedure: freshly collected water is passed through sterile membrane filter, which traps any bacteria, media that is selective & differential limits growth to coliforms, Legionellosis: aka legionnaires" disease, caused by legionella pneumophilia, gram-negative obligately aerobic rod-shaped bacterium, a facultative intracellular parasite that can invade and replicate, common in freshwater and soil inside eukaryotic protists. Legionellosis: l. pneumophilia is an airborne respiratory pathogen contaminated water droplets, people are most often infected after inhaling aerosols of, does not spread person-to-person; doesn"t spread to person, cells invade the lungs and grow within macrophages. Legionella are taken up into a phagosome that never fuses or matures into a phagolysosome. If people in room, can all be infected. Infections are often asymptomatic or produce mild symptoms including cough, sore throat, headache and mild fever.

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Case Study:

Bacteria are everywhereâon our skin, in our food, suspended in our drinking water. Although the
microbial majority is benign, a few bacterial species can make us sick. To safeguard against food- and
water-borne disease, microbiologists routinely screen our drinking water for bacterial pathogens.
Animal feces contain coliform bacteria, microorganisms that inhabit the intestines of warm-blooded
animals. Many coliform bacteria are also found on plants and in soil and water. Coliform bacteria are
not pathogens themselves, but their presence indicates the possibility of finding pathogens. In contrast,
fecal coliform bacteria such as Escherichia coli are found in feces, and their presence in drinking water
indicates fecal contamination. E. coli can also be a pathogen itself, so if E. coli is found in drinking
water there is a good chance that other pathogens are present, too.1
To detect E. coli and other coliform bacteria, microbiologists filter water samples and place the filter in
a Petri dish containing growth medium such as Endo agar. Microorganisms from the water grow and
form colonies, giving an estimate of the number of bacteria in each milliliter of water.
While E. coli forms colored, shiny colonies on Endo agar, other coliforms grow as white or clear
colonies.

Dark colonies = E. coli
White/clear colonies = coliform bacteria
White + Dark colonies = total coliform
bacteria.

The guidelines of maximum allowable limits for total coliforms in drinking and recreational waters vary
by state. Representative limits appear in the table below.2, 3, 4

Table 1. Maximum allowable limits of fecal coliform bacteria
(cells/100 ml)

	Total Coliforms	E. Coli
Drinking Water	0	0
Recreational Waters	400	235

Questions
1. Why would we want to count the number of fecal coliforms in a water sample?
2. Do 400 coliforms per 100 milliliters strike you as very many?
3. How many other types of bacteria might be present in a normal water sample?
4. What problems might Mary encounter when she uses these techniques in Antarctica?

BIOL 2P98 Lecture Notes - Lecture 23: Fecal Coliform, Pathogenic Escherichia Coli, Indicator Organism

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