Do it Yourself TB Test

With a cardboard box, a light source, and some filters, roadside clinics can accurately test for tuberculosis.

By Edyta Zielinska | September 5, 2012

Mycobacterium tuberculosis bacteriaPublic Health Image Library, Ray Butler, CDC

After solving the structure of an enzyme from the tuberculosis bacterium, researchers from Stanford University in Palo Alto created a probe that lights up when the enzyme is present, potentially reducing false negatives inherent to the current diagnostic methods.  The results were published this week (September 2) in Nature Chemistry.

Mycobacterium tuberculosis, the causative agent of tuberculosis, produces and secretes the enzyme BlaC, which breaks down proteins like ß-lactams, present in many antibiotics including penicillin.  Once researchers solved the enzyme's structure, they were able to design a molecule similar to ß-lactam, but which would fluoresce a bright blue glow when broken down by BlaC.

“This method is powerful because it does not rely on access to a microscope and lab facilities,” Bill Jacobs of the Howard Hughes Medical Institute and Albert Einstein College of Medicine in New York, who was not involved in the study, told Nature, nor does it require sputum samples to be cleaned or processed. “And it is much more sensitive than the other tests currently available," able to detect as few as 10 tuberculosis bacteria in a sample.


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Avatar of: anyow


Posts: 3

September 5, 2012

There is a rather horrific textbook-level error, specifically in this fragment:
"...which breaks down proteins like β-lactams, present in many antibiotics including penicillin. "

"β-lactams" are NOT proteins - these are "moieties" (i.e., chemical substructures corresponding to cyclic amides). "β-lactamases" are enzymes (proteins) that hydrolyse ("break") β-lactam bonds in appropriate substrates. Penicillin contains a β-lactam group - but it cannot "contain" a "protein" because penicillin is a small molecule and proteins are large polymers.
Oh my...

Avatar of: Raphael Fernandez

Raphael Fernandez

Posts: 1457

September 7, 2012

As a physician in an environment where pulmonary TB is frequently diagnosed, my pet peeves in diagnosing this disease are in symptomatology and chest x-rays. I get individuals who are asymptomatic but when they undergo chest x-ray for another reason like annual physical exam, they present with one of several vague findings: "chronic inflammatory process," "fibronodular densities," and so on. In terms of x-rays, I've observed there is one PTB diagnosis out of ten vague reports. I feel that radiologists try to be particularly careful in diagnosing PTB, which, on my part, have to try and squeeze out from the patient if he or she does have TB - so a 3-day sputum exam, a lordotic chest x-ray and a patient's trip to a public health center. Having a Do-It-Yourself-TB or an in-office test would be a welcome for me since it only takes 10 minutes to process everything.

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