Researchers at Colorado State University have developed a simple and inexpensive paper-based test that can quickly identify fake or substandard antibiotics.
The test can indicate in around 15 minutes whether an antibiotic sample is the correct strength or whether it has been diluted with filler substances such as baking soda. It works in a similar way to a home pregnancy test as the strip of paper turns a distinctive colour if a fake antibiotic is present and it can be used by an untrained professional.
This is the latest paper-based chemical assay that has been developed by Professor Chuck Harry. His research team included Dr Kat Boehle, who is the first author of the study.
The manufacture and distribution of substandard medicines is widespread. The World Health Organization (WHO) estimates that up to 10% of all drugs worldwide could be falsified, with up to 50% of those being antibiotics. Counterfeit antibiotics are not only dangerous for patients but they also contribute to the escalating antimicrobial resistance problem.
Boehle said: “In this country, we take for granted that our antibiotics are good, we don’t even think twice, but counterfeit and substandard antibiotics are an extremely common thing in other parts of the world. The goal of this project has been to make a cheap detection device that is easy to use; our device costs literally a quarter to make.”
The test uses bacteria which naturally produce an enzyme that can give them resistance to antibiotics by chemically binding to portions of the antibiotic molecule. This enzyme, called beta-lactamase, enabled the device to detect the presence of antibiotics in a given sample.
Users of the test dissolve the questioned antibiotic in water and add the solution to the small paper device. The paper contains nitrocefin so changes colour when it reacts with the enzyme. This is because the antibiotic and the nitrocefin on the paper are in competition to bind with the enzyme in a detection zone.
A good antibiotic dose will result in the paper strip turning slightly yellow because the antibiotic has outcompeted the nitrocefin. Fake or weakened antibiotics will cause the paper to turn red because the enzyme is reacting with the nitrocefin instead.
The device also includes a pH indicator, to determine if a sample is acidic or alkaline and subsequently alert the user to whether a sample has been falsified with filler ingredients.
In the future, the researchers are hoping to make the test more accurate when trying to identifying aspirin.