Biochemists and microbiologists: Aqueous Solutions has a mission for you.
By Josh Kearns
I recently visited two village training centers deep in the
wilds of Tenasserim district (Thailand-Burma border region), where colleagues
and I conducted follow-up inspections on water treatment systems installed by
local trainees during recent months. (Check out our Facebook
page for photos from the trip.)
On this trip and the other routine visits we make to project
sites, in addition to troubleshooting, refurbishment, and data collection to
supplement our research objectives, we perform microbiological testing to
verify drinking water safety. For this task we have been using 3M
Petrifilms, which indicate total coliforms as well as E.coli in a 1 mL water sample.
Over the years, Petrifilms have proved indispensible for
validating our treatment system designs, as they are the most practical and
economical (about US$2 per test) test for microbiological water quality that we
have yet come across.
Their main drawback, though, is the 1 mL sample volume. The
international World Health Organization (WHO) standard for water quality includes
the criteria for E.coli of less than
one colony-forming unit (CFU) per 100 mL. With a 1 mL sample volume, this
standard is thus two orders of magnitude below the detection level of the
Petrifilm test.
However, a new field-oriented commercial E.coli test kit was recently brought to our attention. This method
makes use of a 100 mL sample volume, and a simplified approach to
most-probable-number (MPN) analysis – allowing for better precision and
achieving a lower, WHO-approved detection level.
Unfortunately, at over US$10 per test, this particular E.coli testing system is priced well out
of the range of affordability for small, grassroots NGOs like Aqueous Solutions
and our community based partners. Furthermore, these test kits are rather
bulky, containing a lot of single-use plastic ware. This would make it
cumbersome, if not impossible, for example, to hike distances in remote, rugged
terrain with enough supplies for testing several water sources and treatment
systems. Moreover, the single-use plastic ware presents a safe and
environmentally responsible disposal challenge. (Where we work, it’s not a
matter of phoning up the local EH&S to come by and properly dispose of our
bio-waste!)
We have, however, devised a “hack,” that will allow us to use
the basis of this commercial method but at greatly reduced cost, and with less
bulky and reusable equipment.
The hack is nearly complete, but we lack one key ingredient: 5-Bromo-4-chloro-3-indolyl
β-D-glucuronide, also known as “X-Gluc.” X-Gluc is a chromogenic indicator
that produces a blue color in the presence of E.coli.
So, Biochemists and Microbiologists
Without Borders, your mission, should you choose to accept it, is to help
Aqueous Solutions identify a convenient and economical source of X-Gluc.
The ideal form would be a tablet pre-dosed for 100 mL sample
volume. Sigma-Aldrich
sells tablets, but they are quite expensive. We contacted the company selling
the MPN test kits described above about purchasing their E.coli media pellets but they will not sell them separately from
the test kits. And since the media pellets are proprietary, they will not
provide any information about how to acquire them directly or derive our own.
(As an editorial aside, this is an example of how
intellectual property can inhibit rather than promote innovation, as is commonly
claimed. Our goal is not to undermine the market for this company’s product,
but to build on the extant research and development to adapt the system for
other scenarios where it is currently infeasible – and therefore there
currently is no market. Making
knowledge artificially scarce by keeping the E.coli media formulation proprietary is obviously unhelpful from
the perspective of the many communities who could benefit from water testing…)
Anyway, that’s our pitch. Any leads for how we can secure a
supply of X-Gluc in a cost effective manner would be much appreciated! We are
really excited about this hack and the potential it represents to increase the
sensitivity and robustness of our water system validation field protocol!
As per usual, please feel free to
follow me on Facebook (https://www.facebook.com/joshua.kearns.399), and
“Like” Aqueous Solutions (https://www.facebook.com/AqueousSolutions)!
Thanks for all your great posts, Josh. Have you approached Sigma-Aldrich, et al., and asked them to sponsor your work by donating the X-Gluc? I have been surprised by the generosity of many companies. Peace, Bego
ReplyDeleteGood thought, Bego - I will try that... JK
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