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General Water Sampling Procedures - click here
SAMPLE TYPES: Drinking Water, Cooling Tower Water, Recreational Water, Swimming Pools and Spa Water, Reclaimed Water, Soil, Fuel, Dialysate fluid, Air-conditioning Surfaces, Dust and Air, Food, Food Processing Surface Hygiene, Food Processing Facility Audit
Note that CFU = Colony Forming Unit and means Organisms and mL = millilitres.

Drinking Water
The testing for any specific pathogen in a drinking water sample is not indicated in general situations, either because the laboratory methods are unreliable, the organisms are in too low concentration to be detectable, or the costing for such analyses is excessive. This methods of evaluating drinking water for the likely presence of pathogens is best performed by testing for indicator bacteria of contamination be that faecal or non-faecal in origin. Australian drinking water guidelines recommend that plate count, total coliforms and faecal coliforms be performed, in addition a faecal streptococci count and E. coli count may be useful. For chlorinated water the plate count should be less than 100 CFU/mL for water that is not disinfected the plate count should be less than 500 CFU/mL. Total and faecal coliforms, E. coli and faecal streptococci should be less than 1 CFU/100mL.

Packaged (Bottled) Water, Packaged Ice and Mineral Water
The Australian Food Standards Code requires that microbial quality packaged water and packaged ice meets the following requirements; plate count <100 CFU/mL, Coliforms <1 CFU/250mL and Pseudomonas aeruginosa <1 CFU/250mL. Mineral water must have Coliforms <1 CFU/250mL and Pseudomonas aeruginosa <1 CFU/250mL.

Cooling Tower Water
The plate count of a cooling tower is recommended to be less than 100,000 CFU/mL and a Legionella count to be less than 10 CFU/mL. These analyses should be performed monthly.

See our article reviewing cooling tower contamination of by Legionella

Recreational Water
Recreational water can be categorised into primary (where head immersion is likely) and secondary (where only wading is performed). The National Health and Medical Research Council of Australia (NHMRC) recommends that primary contact recreational water should have a median (of 5 samples collected within a four week period) faecal coliform count not exceeding 150 CFU/mL and that secondary contact water should have a faecal coliform count not exceeding 1,000 CFU/mL for a random sample. However multiple sampling is recommended within a one month period and acceptable results differ for these analyses.

Water used for Washing Produce
The water used to wash fruit and vegetable should meet the standards set by the Australian Drinking Water Guidelines. Australian drinking water guidelines recommend that plate count, total coliforms and faecal coliforms be performed, For chlorinated water the plate count should be less than 100 CFU/mL for water that is not disinfected the plate count should be less than 500 CFU/mL. Total and faecal coliforms should be less than 1 CFU/100mL, although occasional results for total coliforms may be up to 10 CFU/100mL. In regional and rural areas tank, dam, lake, stream or bore water often has high plate count levels and may require some form of disinfection, such as chlorination. It is important to remember that water storage tanks must regularly be cleaned and disinfected.

Swimming Pools and Spa Water
The NHMRC recommends for heated spa pools that the plate count should be less than 100 CFU/mL and that a Pseudomonas aeruginosa count be less than 1 CFU/100mL. Other authorities recommend a total coliform count, faecal coliform count, coagulase positive staphylococci count and E. coli count of less than 1 CFU/100mL. In some situations a Legionella count should also be performed where the result should be less than 10 CFU/mL. 

Reclaimed Water
The NHMRC and the Australian Water Resources Council recommend that unless otherwise approved by appropriate authorities, treated reclaimed water should have a faecal coliform count not exceeding 1,000 CFU/100mL. However multiple sampling is recommended at half hourly intervals and acceptable results differ for these analyses.

Soil
Whether to investigate soil contamination or based on government requirements bacterial analyses for faecal coliforms and/or Escherichia coli are often performed on environmental soil samples. Potting mixes can also be analysed for the presence of Legionella.

Fuel
The fungus Cladosporium resinae and other fungi can propagate in kerosine, diesel and aviation fuel; this can cause serious engine damage. This analysis can be performed on fuel storage tanks to detect this and other fungal elements.

Dialysate
The Australian Kidney Foundation and the Australian and New Zealand Society of Nephrology Joint Subcommittee on Dialysis and Transplantation. 1993, and The American National Standards for Haemodialysis systems (RO-5-1992) state that water used for the preparation of dialysate should have a plate count not exceeding 200 CFU/mL and that the dialysate plate count should not exceed 2,000 CFU/mL.

Air-conditioning surfaces, dust and air
The examination of dust and air-conditioning surfaces (including ducts) for a quantitative measurement of bacteria and fungi per gram or per square centimetre, respectively, can be of assistance when investigating a dysfunctional building or being proactive in air quality maintenance. Air samples for microbiological analysis are based on either a filtered air sample (eg 20 litres) or an equivalent sampling technique utilizing a centrifugal air sampler. Results are given as organisms per cubic metre. Analyses include bacteria, yeast and moulds and thermoactinomycetes. Identification of dominant bacteria and fungi can also be provided.

Food Quality
The microbial quality of food is constantly under review by both the public and health authorities. All food processors (from manufacturing firms to school tuck shops) are required to ensure that safe food is supplied to customers. Bacterial food poisoning is the most common cause of food borne illness. Generally more than 90% of the cases of food poisoning each year are caused by Salmonella, Staphylococcus aureus, Clostridium perfringens, Campylobacter, Listeria monocytogenes, Vibrio parahaemolyticus, Bacillus cereus and pathogenic Escherichia coli. These analyses and other organisms, both pathogenic and indicator organisms are routinely performed by our laboratory. For specific information on food poisoning try one of these sites: "The Bad Bug Book",   The Australian Food Safety Web and Bacterial Food Poisoning by Al Wagner Jr., Texas Agricultural Extension Service.

Food Shelf Life Evaluation
When evaluating the microbial quality of a food, to be held at a controlled temperature, there are two variables to consider, the time interval of performing the analyses and the organisms to be analysed.

It is recommended that as a minimum the food be evaluated at Day 0 (day of production), Day Max (day at which expected shelf life is complete) and Day Max+50% (Day Max plus half the number of the expected shelf life). For example, if a shelf life was set for 10 days, testing would be performed at Day 0, Day 10 and Day 15. Obviously by increasing the number of samples taken on a day and increasing the frequency of evaluation during the period more information and greater accuracy of results will occur. The Day Max+50% sample provides valuable data to the manufacturer that the product will remain in good microbial quality if consumed (as often is the case) after the "Use By", "Best By" or "Expiry Date".

When evaluating shelf life there are three groups of organisms to consider; indicator (such as plate count, yeast and moulds, coliforms, Enterobacteriacae, faecal coliforms etc.), spoilage (such as lactic acid bacteria, Brochothrix thermosphacta, Pseudomonas, yeast and moulds etc.) and food pathogens (Salmonella, Staphylococcus aureus, Clostridium perfringens, Campylobacter, Listeria monocytogenes, Vibrio parahaemolyticus, Bacillus cereus and pathogenic Escherichia coli etc.) In general, Day 0 to Day Max samples are only tested for indicator and spoilage organisms and Day Max+50% samples are tested for all three groups. The specific organisms selected from each group will depend on the type of product under evaluation.

There is also a form of shelf life evaluation called "Temperature Abuse Shelf Life Evaluation" where the product is held at higher temperatures to mimic consumer abuse of storage conditions. In this situation Day 0 and Day Max are only performed and the analyses performed on Day Max includes all three groups of organisms.

Food Processors Surface Hygiene
A major component of the hygiene of a kitchen, processing line or food production plant is the control of the cleaning of equipment, storage tray, utensils and preparative benches. A simple inexpensive test provides a quantitative test with has a sensitivity down to 0.4 CFU/square centimetre. The Australian standard (AS 2997-1987) states that an acceptable limit to indicate satisfactory cleaning operations by this method is less than 6 CFU/square centimetre.

Food Processors Laboratory Audit
Many large food processors have in-house laboratories to perform some or all of their quality control evaluations. When these laboratories are not NATA accredited, an audit can yield useful information on the quality of the facility, training requirements of staff, and areas in which new technology could be used. Even though these laboratories may not meet, or may be preparing to meet NATA requirements for testing, it is useful to be aware of areas where simple changes can be made that will improve the specificity, sensitivity and reproducibility of analyses.

Food Processors Facility Audit
Another service offered is the performance of external audits of kitchen/food preparation facilities. Our experience in performing this service for a national food outlet for all its stores in Queensland and the Northern Territory has been well developed. The audit takes approximately one to three hours depending on the customers requirements. The full audit evaluates the facility based on food and surface microbiological sampling, temperature logging and area inspections ensuring both hygiene and our customers standards are being maintained.