The Compartment Bag Test (CBT)

Quantitative E. coli Water Quality Test Kits

The Aquagenx CBT E. coli Kit simplifies on-site water quality testing where it was previously too difficult, impractical and costly. It is a field-level test that is optimized for low resource, rural and disaster/emergency areas.

Easy color-match scoring lets you determine Most Probable Number (MPN) of E. coli in a 100 mL sample.


  • Compact and lightweight
  • Anyone can use with little training
  • No electricity, labs, cold chain, expensive equipment required
  • Works at variable temperatures, constant temperature control not required
  • Ambient temperature incubation at 25° Celsius and above
  • Test results in 24-48 hours depending on ambient temperature
  • Meets World Health Organization (WHO) Guidelines for Drinking Water Quality


The Compartment Bag Test was developed by Dr. Mark D. Sobsey.

CBT E. coli Kit – 10 Pack

Sold by the kit. 10 tests per kit.
Product Number: ECCBT10
Shelf life of E. coli medium: 2-years from date of manufacture

Kit includes:

  • 10 compartment bags
  • 10 E. coli test buds
  • 10 100 mL plastic sample bottles
  • 30 chlorine tablets for sample disinfection
  • 1 seal clip (extra clips sold separately)

Kit Dimensions: 8 x 8 x 4.5 inches
Kit Weight: 1 pound 7 ounces

CBT E. coli Kit – 50 Pack

Aquagenx CBT II Kit

Sold by the kit. 50 tests per kit.
Product Number: ECCBT50
Shelf life of E. coli medium: 2-years from date of manufacture

Kit includes:

  • 50 compartment bags
  • 50 E. coli test buds
  • 50 100 mL Stand-Up Whirl-Pak Thio Bags
  • 1 seal clip (extra clips sold separately)

Kit Dimensions: 7.5  x 7.5 x 4 inches
Kit Weight: 1 pound 8 ounces

CBT Kit + Mobile Data Collection

Comparison of Testing Methods for E. coli


 Presence/AbsenceMultiple TubePlate and Film MethodsMembrane FiltrationAQUAGENX CBT KIT
Electricity (see footnote 1)YesYesYesYesNo
Controlled Incubation (see footnote 1)YesYesYesYesNo
Ambient Temperature Incubation (see footnote 2)MaybeMaybeNoMaybeYes. 25 degrees Celsius and above.
UV LightMaybe; variesMaybe; variesMaybe; variesMaybe; varies (see footnote 3)No
Extra and/or Bulky Equipment and Other MaterialsYesYesYesYesNo
Cold StorageNoMaybeMaybeMaybe (see footnote 4)No
Quantified Test ResultsNoYesYesYesYes
Trained TechniciansNoYesYesYesNo
Compact, Easy Transport in FieldNoNoNoNoYes
Sterilize Reusable PartsNoYesYesYesNo
Decontamination IncludedNoNoNoNoCBT E. coli Kit 10-Pack includes chlorine tablets for sample disinfection.

(1) Most tests specify incubation at a specific temperature, which requires use of an incubator powered by electricity; some tests have heat-sensitive bacteriological media which requires temperature control, often refrigeration, for storage.

(2) Most tests recommend specific temperatures for incubation, such as 35-37° Celsius or 44.5° Celsius. Use of ambient temperatures is not recommended and many tests have not been validated for performance at ambient temperature.

(3) Many tests rely on detecting E. coli growth by the blue fluorescence produced by the hydrolysis product of a specific fluorogenic Beta-D-glucoronide substrate.

(4) Many tests come with prepared culture media that must be stored cold or else they will degrade. Those tests that do not usually require that the dehydrated bacteria culture medium provided be reconstituted in reagent water and either boiled or steam sterilized (autoclaved) for use.

“Being able to perform our own reliable quantitative testing saved our organization time and money. We will continue to use the CBT because we routinely test water sources for the presence of E. coli, and we now prefer to have a clear, quantitative understanding of the magnitude of fecal contamination.”

Ted Barlow

Operation Blessing International

“The CBT builds trust for our beneficiaries by providing evidence that makes them confident our water filters generate safe drinking water. Because of its efficiency. It enables our staff to test water on-site rather than having to collect samples to be sent to a lab. We’ll continue using the CBT as our ongoing microbiological water quality test.”

Vann Chhorvy Vanny

Clear Cambodia