1. What are some important microbial safety tests of water samples?
2. What materials are required for counting colonies?
3. What materials are required for identifying bacteria in the water?
4. Is it important to identify fungal yeasts and molds in water samples?
5. Is it important to identify bacteria found in non-drinking water?
6. What are some approaches to tracking the source of contaminated drinking water?

1. What are some important microbial safety tests of water samples?

• Counting bacteria and yeast colonies in water samples.
• Identifying bacteria that are potentially from human feces.
• Tracking potential sources of human feces contamination using antimicrobial resistance profiles.

2. What materials are required for counting colonies?

Agar petri plates inoculated with a water sample. If the water appears to be significantly contaminated, several dilutions of the water sample should be plated separately, e.g. 1/10 and 1/100 dilutions. The colonies can be counted manually, or automatically using the BIOMIC V3 Microbiology System or TRINITY V3 Microbiology System.

3. What materials are required for identifying bacteria in the water?

Many bacteria commercial test kits are available. Some broth based kits only detect lactose fermenter gram negative bacteria, and thus give a positive or negative reaction, indicating a probable Enterobacteriaceae (fecal flora). If positive, the broth can be inoculated into a gram negative fermenter kit to speciate the bacteria. API^® (bioMerieux) identification panels are commonly used. Chromogenic agar plates (available from several commercial vendors) can also be used for colony counts, and to determine the identity of the species that are lactose fermenters. The BIOMIC V3 Microbiology System automatically reads and interprets most commercial bacteria species identification panels (API^®, RapID™, Crystal™) , and counts and identifies the colonies on chromogenic agars (CHROMagar™ from BD, etc).

4. Is it important to identify fungal yeasts and molds in water samples?

Probably not. These do not tend to be pathogens transmitted by drinking waters.

5. Is it important to identify fungal yeasts and molds in water samples?

Sometimes. When looking for a possible source of contamination of drinking water, testing of underground and surface water supplies can be important. The testing procedures above are used. However, testing water supplies that do not contribute to drinking supplies, for example, water in swimming pools, lakes, streams, and supplies for plant irrigation, animal drinking, and industrial purposes can be very costly and provide results that are not likely to be useful, and may be misleading.

6. What are some approaches to tracking the source of contaminated drinking water?

One relatively simple cost effective approach to tracking bacterial contaminants back to their source is using antibiograms. The standard antibiotic disk diffusion test provides antibiotic resistance pattern phenotype “fingerprints”. These antiobiograms can then be compared with isolates from many water samples in an attempt to identify common sources with the same pattern. The BIOMIC V3 Microbiology System can be very useful in automatically reading, interpreting and storing this antibiotic resistance pattern information.

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References

The following references may be useful to provide more details on the above test methods.

 

Analytical Methods for Microbiological Water Quality Testing (World Health Organization)

Indicator of Microbial Water Quality (World Health Organization)

United States Environmental Protection Agency (US EPA) Microbiological Methods/Online Publications

US EPA Home Water Testing

Water Education from www.freedrinkingwater.com

Water Testing Bacteria, Coliform, Nuisance Bacteria, Viruses, and Pathogens in Drinking Water (Wilkes College)

Bacteria in Drinking Water (University of Missouri)

Test Your Water For Coliform Bacteria And Nitrate (University of Illinois)

View Main Microbiobial Water Testing

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