© 2006 DBI Europe
Design door Serif
Think about the problems that might occur and then select the right BART™ to get to the heart of that problem.
BART™ testers provide a very easy way to test for active bacteria in water, Why is that?
Active bacteria are the ones that can cause problems in the water and to the people using the water. There are several different bacteria that be active in water but under different circumstances. Selecting the right BART™ tester(s) to determine the activities can be very important. Think about the problems that might occur and then select the right BART™ to get to the heart of that problem.
The BARTs™ are classified into several product groups that look for specific bacterial activity. If you analyze the problem, you can narrow the possibilities of activity, then select the appropriate BART™(s) for the category of bacterial activity.
How can the BART™ tester help?
The BART is easy to use, tells you something about how active the bacteria, which types of bacteria are active in the water sample. Additionally, if you are applying a treatment then the effectiveness of that treatment can be measured using the selected BART™ testers.
The BART testers can provide a variety of information that can be useful in understanding bacterial activity. They provide three key features to bacterial water analysis. First, they can provide you an interpretation on the bacterial activity in a given water source. Secondly, they can address what types of bacteria are currently active in the water source. And finally, they are easy to use in both laboratory and field study.
How do you measure bacterial activity?
In setting up a BART tester leave it at room temperature and look periodically. That time interval is called the time lag and can be used to determine activity. Remember that the shorter the time lag then the greater is the activity and the bigger the population.
The BART testers operate at room temperature to stimulate bacterial reactions. These reactions are listed in reaction charts to help identify, and classify, the bacteria. The tests produce the various reactions that are noted by the technician by recording the reaction code, time and date. The lag time from start date to reaction is then used to calculate the approximated activity. Remember that the quick the lag time the higher the population.
What temperature should I use to test the water samples?
When the BART is being used in the field or office, no extra equipment is needed to operate at room temperature (nominally 22oC) and so that is a preferred temperature. However, water samples can commonly come from sources as cold as 0oC or as hot as 45oC. Room temperature is in the middle of that range and will tend trap much of the activity. If you have a special need or a BART reader then 28oC or 37oC can be applied
What makes a BART™ tester work?
The tester has been designed to provide a range of environments from very reductive in the base cone to very oxidative around and under the floating ball. This means a gradient is created vertically in the tester that can encourage many different types of bacteria to grow. To encourage different communities of bacteria to grow then a crystallized pellet of chemicals that are selective nutrients are placed in the base cone of the tester. These selective nutrients diffuse up and cause only the bacteria being investigated to grow and trigger reactions. The BART tester is therefore a very “friendly” environment created to maximize the detection of the active bacteria. This is done by a combination of looking for a reaction and timing that event to gauge the activity
How accurate are the BART™ testers?
Common trends do emerge although every 15mL sample used for a BART test will be a little different. On a water sample when duplicate tests are performed, the time lags commonly vary by less than 5% and the same sequence of reactions is observed. Some operators use a staged approach to testing using BARTs. They will set a minimal time lag (such as 4 days) that would indicate that the water was OK and no treatment is required. When a test comes in with a time lag of 3 days then this could be a problem since the bacteria are getting more active. Before running an expensive treatment these operators will now run duplicate tests to determine whether that result was not typical. If the duplicates also show shorter time lags (in this case, less than 4 days) then a treatment is undertaken. After treatment the tests should show the activity now at 4 days or better. Some operators therefore do routine BART tests to monitor the activity reacting with duplicate tests when a problem may be emerging (i.e. time lags shortening)
Are these BART™ tests considered regulatory tests?
Getting any new test accepted by the regulatory process is a long and complicated
process. For the BART testers, this is a particularly challenging process because
there are no easy comparative tests. In microbiology, the agar plate remains a standard
but it does not allow the variety of bacteria to grow that will grow in a BART tester.
Membrane filtration is another standard but it suffers from serious overgrowth issues.
ATP (adenosine triphosphate) analysis has become a new standard but it only quantifies
the total number of active cells regardless of their relevance to the test. The BART
tester’s process of getting regulatory approval has been slow while we build up the
perfect the systems. Three testers have got Environmental Verification (IRB-
What is the shelf life on a BART™ tester?
The standard shelf life for most BART testers is four years provided that the aluminum foil pouch has not been breached. Once the foil pouch has been opened then it is recommended that (1) you use the BART testers from that opened pouch as quickly as possible; and (2) that the unused BART testers are kept in a refrigerator with the foil pouch closed shut with tape. Note that these pouches hold either three field testers or five laboratory testers.
Is it better to load the BART™ testers in the field and then take then back for testing or take the sample back and fill the BART™ testers where the tests are going to be done?
Once the BART™ tester has been filled with the sample it is very important to keep the testers upright (within 5o of vertical) and avoid vibration. This is to ensure that the different environments set up quickly within the tester. Minor vibration or a gentle motion (such as at sea) does not appear to affect the performance of the BART testers. If you are going to transport the water sample then let it come up (or down) to room temperature as it is shipped (less than four hours). If shipping is going to be over four hours then ship over ice. The answer then depends upon the local conditions but setting the sample up as quickly as possible with no subsequent major disturbance of the tester is the prime concern.
What are the advantages of me doing BART™ tests when I could send the samples to all labs?
If you want be to in control of bacterial problems then the sooner that you find out then the quicker you can take action. BART testers give you the opportunity to keep right on top of the events without having to wait for a laboratory to complete the tests and send you the results. Remember the laboratory can always confirm (or deny) what you have found using the BART testers but the bottom line is that you are “in the trenches” and you need to know quickly when there are incoming bacterial challenges. You will get familiar with the reactions and time lags that means the water is not biofouled but you will also see when a problem is beginning to emerge sometimes even before your instruments tell you.
Would a BART™ tester be economical to use compared to sending the sample to a laboratory?
The savings are twofold. First you can set the test up straight away when the sample has been freshly taken (shipping the sample to a laboratory takes time and the microbes in the sample would change in their activity level during the shipping to create a compromised sample). Second you do not have to pay the costs of shipping the sample to a laboratory or the laboratory fees for the testing. The costs are your time and the cost of the BART tester itself. Remember that you have a concern with the results and want a confirmatory you can either repeat the test yourself (preferably in duplicate) or you can send the test properly packaged to a certified microbiology laboratory.
What is the sensitivity of the BART™ tester to detecting bacteria?
If you were to take a one liter water sample, the sensitivity of the tester would be to detect down to 67 bacteria in that one liter of sample if it was all tested. For the BART tester, the limit of detection would be one cell in 15mL or 0.07 active cells per mL BART sensitivity is dependent upon the cells inside the sample being active. It is these active cells that can present the greatest risk and that is one reason why the term “predicted active cells” is used.
Is the 15mL of water sample used in the BART™ tester enough to get accurate results?
15ml is an odd number but through about five years of research in the 1980s it was found the smaller volumes did not allow the various environments within the tester to get established (even when 10mL was used!) and so that volume is the minimal volume to achieve repeatable and interpretable data.
What does p.a.c mean and how does it relate to colony forming units?
Time lags are converted by standard formulae to cell population numbers. Traditionally, the colony forming units have been the standard because they relate to a count of individually growing colonies on an agar plate. For the BART tests, the colonies are not counted because activity can be recorded as time lags. From this the predicted active cells (p.a.c.) can be calculated which is similar to a colony count.
Does the occurrence of bubbles on the walls and scattered under the ball have any meaning?
Bubbles can be a menace in a BART test due to a number of reasons. These include:
(1) oxygen coming out of solution as a cold water sample warms up the room temperature;
(2) covert gas production such as carbon dioxide, methane and hydrogen by indigenous
bacteria in the water that is not a part of the recognized reactions; and (3) geomagnetic
effects wherein packets of gas bubbles are seen to cluster on one side of the tester.
The only gas events recognized are those that occur when a gas foam ring forms around
the ball (common when anaerobic bacteria are present during an IRB-
What unusual places have the BART™ testers been used?
BART™ testers have been used extreme environments such as at depths of 10,000’ in the deep ocean, down 1,500’ in experimental mines, in icy conditions with the temperatures just above freezing and in brines approaching saturation. The have also been used to detect bacteria in rain and snow and also in the gas hydrates in the Gulf of Mexico. The robustness of the design extends the ability to detect the “undetectable!”