Water Microbiology Section

Water Microbiology for State and Federal Agencies

Iron Bacteria | Swimming Beach Testing | Surface Water Testing | Sulfate Reducing Bacteria

Total Coliform Testing for Drinking Water | Heterotrophic Plate Count | Cryptosporidium and Giardia Testing

E.coli Testing for Drinking Water | Pseudomonas aeruginosa | Salmonella and E.coli O157

Helicobacter pylori

Iron Bacteria:
Iron bacteria are naturally present in surface waters and soils and sometimes may find their way into wells. Iron bacteria do not cause illness, but are considered a nuisance bacteria. These bacteria can oxidize iron or manganese dissolved in water around their bodies. Large populations can produce an orange/ brown slime that builds up inside well screens, pipes, and plumbing fixtures. Indications that iron bacteria may be present include the presence of an unpleasant odor and/or brown-tinted water or fixtures. Samples for testing should be collected when the water system has been inactive for several hours (e.g. early morning). A sample volume of 100 ml is requested; there is no time limit between sample collection and processing. In the laboratory, the sample is processed and examined under a microscope for iron bacteria. The genera and estimated number of iron bacteria are reported.

Sulfate Reducing Bacteria:
Like iron bacteria, sulfur bacteria do not cause illness, but are nuisance bacteria. Sulfate reducing bacteria and iron bacteria can co-exist in the same environment. The most important group of sulfur bacteria are those that reduce sulfate to sulfuric acid, which leads to corrosion of water conducting systems (well casings, pipes, cement, etc.). These bacteria cause an unpleasant sulfur (i.e. a "rotten egg") odor in the water. The laboratory assay involves the culturing of live bacteria from a 100 ml sample. The sample must be shipped under 10°C and cultured within 24 hours of collection to insure any bacteria will be alive to grow in the medium. A 21-day incubation period is required before the sample can be called negative.

Cryptosporidium and Giardia Testing:
These are parasites that must be swallowed in order to cause disease. The organisms are spread by the fecal-oral route. The illness caused by Cryptosporidium is characterized by watery diarrhea and abdominal cramps. The illness caused by Giardia is characterized by nausea and fatigue, followed by watery diarrhea that can last more than 10 days. The detection method recovers both organisms. Contact the Water Microbiology Unit for specific information about the tests, or to discuss other possible routes of infection.

Swimming Beach Testing:
Beaches where swimming is allowed should be tested for water quality before the swimming season begins, to get a baseline of contamination due to natural wildlife or run-off, and each week thereafter until the area closes. A membrane filtration test is used to give a fecal coliform or E.coli count per 100ml of water. A general rule for quality maintenance is that no one fecal coliform count should exceed 400 CFU/100 ml, and that the average of 5 samples over 30 days should not exceed 200 CFU/100 ml. A general rule for guality maintenance is that no one E.coli count should exceed 235 CFU/100ml and the average count of 5 samples over 30 days should not exceed 126 CFU/100 ml for E. coli. Counts will vary during the season depending on usage and environmental factors. Beaches are regulated by local ordinance.

Video - Beach Water Collection for E. Coli Testing

Using the appropriate sampling protocol to collect beach water samples for E. coli testing is critical to effectively protect the health of public beach users.  This 12 minute video provides instructions on how to properly collect beach water samples for E. coli testing.  Public health sanitarians, resort owners and anyone required to test swimming beaches for E. coli will find this video a valuable resource. (Windows Media Player is required for viewing).

High-bandwidth video (2 Mbps)

Low-bandwidth video (81 Kbps)

The video was produced by the Wisconsin State Laboratory of Hygiene, with funding provided by the State Lab of Hygiene, the Wisconsin Department of Natural Resources and the Wisconsin Department of Health and Family Services.

Total Coliform Testing for Drinking Water:
"Coliform" are gram negative rod-shaped bacteria that posses the enzyme b-D-galactosidase allowing them to ferment lactose. This is a large group of organisms that includes several genera. The most common genera are Escherichia, Klebsiella, Serratia, Enterobacter, and Citrobacter. These organisms are not pathogenic, but their presence indicates the water system has been contaminated from an outside source and may contain organisms that can cause disease. The test routinely used at WSLH to detect total coliform bacteria is a presence-absence enzymati days . Water must be tested within 48 hours of collection (preferably 24 hours).

E.coli Testing for Drinking Water:
E.coli is an indicator organism of fecal contamination. The only natural habitat for E.coli is the intestinal tract of warm blooded animals. Therefore, the presence of E. coli in a drinking water sample is an indication of fecal contamination of the water supply. The test for detecting E.coli in a water sample is run simultaneously with the Total Coliform test (see above).

Surface Water Testing:
Various tests are used to investigate recreational water, stream or lake pollution, and wastewater treatment systems. Aliquots from water samples are filtered and analyzed with selective media where only the target organisms will grow. The tests take between 24 to 48 hours to complete and the results are reported as the number of colony forming units (CFU) per 100ml of water. Samples must be tested within 8 hours of collection for enforcement purposes and within 24 hours for monitoring purposes. All samples must be received under 10°C. Tests for the following bacteria in surface water are available:

• Fecal Coliform: This test detects all E.coli and some Klebsiella bacteria.
• E. coli: This test detects only E. coli, who's only natural habitat is the intestinal tract of warm blooded animals. The recreational water guideline is 126 CFU/100ml, averaged from 5 samples during a 30-day period.
• Fecal Streptococci: This test detects a number of species of the genus Streptocococcus that give a positive reaction with Lancefield's Group D antisera and have been isolated from the feces of warm-blooded animals. The common species are S. faecalis, S. faceium, S. avium, S. bovis, S. equinus and S. gallinarum. This test has a false-positive rate ranging from 10 to 90%.
• Enterococci: This refers to a subgroup of the fecal streptococci that includes S. faecalis, S. faecium, S. gallinarum and S. avium. The enterococci are used to indicate water quality. The recreational water guideline is 33 CFU/100ml, averaged from 5 samples during a 30-day period.

Heterotrophic Plate Count:
This test estimates the number of live heterotrophic bacteria and measures changes during water treatment and distribution. Samples must be received under 10°C and within 8 hours of collection for enforcement.

Pseudomonas aeruginosa:
This test is generally used to measure the disinfection efficiency of whirlpools, pools and spas.

Salmonella and E.coli O157:
The WSLH provides tests for these specific pathogens. However, the methods are still experimental. Contact the Water Microbiology Unit for specific information about the tests.

Helicobacter pylori are a bacteria species that cause peptic ulcers in humans. Currently, the human and animal (warm-blooded) stomach and intestinal tract is the only proven domain of the pathogen. However, research shows evidence that H. pylori also exists in the environment (surface & ground water, manure, vegetables, etc.) and could be transmitted to humans who unintentionally consume the contaminants.