Measuring bacterial heat could reduce cost of diagnosing TB

Researchers in Switzerland hope to reduce the time and cost of diagnosing tuberculosis (TB) by measuring the heat bacteria produce as they grow.

A team led by Dr Olivier Braissant from Lausanne University is developing a method using microcalorimeters, which produce unique electrical signals based on the heat given off by different chemical, physical or biological processes.

This could remove the need for scientists to grow samples of TB bacteria in a lab for examination, which can take up to 57 days — the microcalorimeter method takes less than two weeks.

Other faster methods have been developed but the researchers say that these are expensive and require equipment and materials often not available in developing countries.

This can include consumables such as fluorescent or radioactive probes, adding to the initial cost of equipment, which can be around $39,000 (£23,700).

Simple calorimeters can be built for around $1,000 (£600). The researchers used a computer to amplify the microcalorimeter signal and produce a graphical footprint that is unique to each species of bacteria.

Dr Braissant’s team has shown that this method works in a laboratory — results are published today in the Journal of Applied Microbiology  — and the team are now planning to test it in the field.

‘Microcalorimeters have already been shipped to Tanzania and we hope to start a first validation of our approach in the field before the end of the year,’ said Braissant.

The method could also be used to test the effects of new types of antibiotic on the bacteria, as multiple samples from the same person can be tested for bacteria growth at the same time.

One third of the world’s population is infected with TB and in 2009 there were 1.7 million deaths from the disease. The highest number of these deaths was in Africa.