Microbiological Media

What makes BTI Products media different from other commercially available media?
There are several reasons why BTI Products’ media is different from competitors’ media and ultimately provides more accurate and reliable testing of industrial samples:

1. Relevance to industrial testing - BTI Products’ media has been developed through years of research and testing to provide conditions favorable to the growth of specific groups of real-world microbes.  Other commercially available media is typically formulated to grow laboratory strains of bacteria which often limits its ability to grow microbes found in real-life industrial environments.
2. Sensitivity - BTI Products’ approach allows for detection of many more microbes than is possible using other methods, while still having the broadest detection range of any test method (one microbe per milliliter to as high a detection limit as you may want).
3. Detection/recovery - Putting our media into sealed glass bottles allows us to control the gases in the liquid medium and in the headspace, which provides an environment even more favorable to rapid growth of microbes of the desired types.  This sealed environment also prevents drying of media, which is a problem with agar plates and dipsticks).   
4. Eliminates contamination - The enclosed environment inside the glass bottles eliminates contamination of the media due to exposure to air, dust, and contact with surfaces and/or fingers.
5. Tests any type of sample - Liquids, biofilms, swabs, corrosion products, soils, effluent, fuels, etc. can all be tested using BTI Products’ media.
6. Ease of interpretation - Positive reactions are definite and rely upon color change or clouding of media.

 
Which type of media should we use to test?
The type of media best-suited to your testing application depends upon the type of environment you are testing.  Because different groups of bacteria thrive under different conditions, it is helpful to know what the predominate conditions are of the sample you are testing.  For example, locations that are consistently exposed to air and/or oxygenated soils are likely to have higher numbers of bacteria that require oxygen for growth (e.g., aerobic bacteria).  Locations that are consistently devoid of oxygen tend to have more bacteria that thrive in anaerobic conditions (e.g., anaerobic bacteria, acid-producing, and sulfate-reducing bacteria).  The best way to determine which groups of bacteria are most prevalent in the environment you are testing, is to test using media belonging to all the various bacterial groups.  BTI Products MICkit® Comprehensive allows testing of a wide range of bacterial groups and chemistries and is appropriate for many different applications.

Once problematic bacteria have been identified using one of our Diagnostic Test Kits, ordering trays of media or custom test kits like our MICkit® 3-C will allow you to test for those particular bacterial groups.


Which types of samples can be tested using BTI Products’ media?
Our media can be used to test any type of sample including liquids, biofilms, swabs, corrosion products, soils, effluent, fuels, etc.


What is the detection limit/range of BTI Products’ media?
Our media has a detection range of one microbe per milliliter to as high a detection range as you want. 


How can the detection range of media be extended or changed?
The detection limit of a media dilution series (i.e., two or more bottles of one type of media) can be extended in many ways:

1. Add more bottles of media to the series.
2. Change the volume of sample you test (e.g., instead of inoculating 1 milliliter (ml) of sample into the first media bottle, you might use 0.1 ml (one-tenth ml) of sample to increase the detection range 10-fold.
3. Change the volume of the amount of media/sample mixture transferred from bottle to bottle (e.g., instead of transferring 1.0 ml of media/sample mixture from bottle to bottle, you might transfer 0.1 ml, or one-tenth ml, of media/sample mixture to increase the detection range 1,000-fold.
4. Combine any of the above three options to create even more options for changing the dilution series.

 
What is a serial dilution and how does it work?
Serial dilution is the stepwise dilution of a substance in solution—in the case of BTI Products media, growth media in which a specific group of microbes (e.g., SRB) can grow.  The first bottle in the dilution series contains the most microbes.  Depending upon how much sample is transferred from the first bottle to the second bottle, the second bottle contains one-tenth (1/10) or one-hundredth (1/100) as many microbes as the first bottle.  The third bottle contains 1/10 or 1/100 as many microbes as the second bottle, and so on.  This allows detection limits of one microbe per milliliter (ml) of sample to unlimited numbers of bacteria in samples, depending on how the dilution series are done and how many bottles are used.


How are media results interpreted?
BTI Products’ media relies upon clouding or color change of media to indicate a positive reaction.  Following are brief descriptions of positive reactions in BTI Products’ media. 

• BTI-AERO (yellow-capped bottles) detect the presence of aerobic bacteria (AERO).  These bottles will turn cloudy and/or have slime, which appears as sheets or clumps of material, if aerobes are present.
• BTI-ANA (blue-capped bottles) detect anaerobic or facultatively anaerobic bacteria (ANA).  These bottles will turn cloudy if anaerobes are present.
• BTI-APB (red-capped bottles) detect organic acid-producing bacteria (APB).  These bottles will turn cloudy orange or cloudy yellow if APB are present.  A color change without cloudiness is not a positive reaction for APB.
• BTI-IRB (white-capped bottles) detect iron-related bacteria (IRB). A  positive reaction for IRB results when the media turns rust-colored or green-black (either with or without the formation of deposits) or when iron is deposited in the bottom of the bottle, usually turning the media from golden to clear.  Iron deposits may be rust, white, black, gray, or green in color.  A cloudy appearance, formation of slime in the bottle, or a combination of both is not a positive reaction for IRB.
• BTI-LNB (purple-capped bottles) detect viable low nutrient bacteria (LNB).  These bottles will turn cloudy if LNB are present.
• BTI-SRB (green-capped bottles) detect sulfate-reducing bacteria (SRB).  These bottles will turn black or will have black slime form on the iron nail along the bottom of the bottle if SRB are present. The presence of black or gray flecks is not a positive reaction for SRB.

These descriptions, along with pictures of positive reactions, are also included in our Diagnostic Test Kit Instructions.  In addition, for clients using our Diagnostic Test Kits, we offer MICkit® & MIPkit™ Test Kit Reports which provide written reports on test results and interpretations of the data.


What types and levels of bacteria should be of concern?
Numbers and types of bacteria that should be a cause for concern depends upon several factors, including:  the type of facility being tested, the type of sample (e.g., liquid, soil), and whether or not the facility is being treated specifically for bacteria.  To discuss levels of concern for your particular application, please contact us.


Is your media toxic or hazardous to personnel using it?
As received (i.e., uninoculated), BTI Products’ media is not toxic or hazardous to either personnel or the environment.  Please refer to the Material Safety Data Sheets (MSDS) for individual media for further information.

The types of bacteria recovered and grown using BTI Products’ media are not known to be harmful to humans or the environment (since the bacteria grown in the media are non-pathogenic types typically found in our everyday environments).  Once media has been inoculated and contains living bacteria, disposal of media bottles should be done according to the regulations provided in the Product Disposal section of this website.

Our fixative solution (PBS/F) contains a very small amount of formalin to kill the microbes in the sample for microscopic examination.  However, because of the way the PBS/F is packaged, the user should never come into contact with the solution in this bottle.


How should the media bottles be disposed of after they’ve been used?
Please see the Product Disposal section of this website which addresses this question.