A bug’s death

A rapid, non-invasive device to diagnose bacterial infections is being developed by an international team of engineers and clinicians, with the help of a €1.67m (£1.2m) grant from the EC.

A trauma or burns patient may show no signs of infection, but bacteria could be beginning to colonise their wounds. Results of microbiological swab tests typically take three days to arrive, but in the meantime the patient may have become critically ill. The aim of the project is to design a sensor that would give results in half an hour, so any infection can be treated before it takes hold. Bacteria give off specific cocktails of volatile chemicals as they grow, and the organism could be identified by ‘sniffing’ these.

‘We’ve combined forces with sensor labs in Italy and Lithuania to create a hybrid gas sensing array to discriminate the volatiles,’ said Prof Krishna Persaud of the University of Manchester‘s school of chemical engineering and analytical science. ‘The idea is to create an array of sensors, each of which has a different response to the volatiles. By using pattern recognition based on neural networks, we hope to create a system that will give real-time diagnosis.’

Two different forms of gas sensor are being combined. One is based on metal oxides, typically tin oxide combined with rare metal oxides, which become semiconductors on heating. The other uses organic semiconductors — conducting polymers that work at room temperature. A hybrid mixture would create a gas sensing array that detects a wide range of different volatiles. ‘We are using the two together because the organic semiconductors detect polar chemicals, and the oxides non-polar ones,’ explained Persaud. ‘Although the techniques are both well-established, no one has brought them together to make a hybrid array before.’

Another technical challenge is posed by getting the volatiles into the sensors. ‘We are dealing with very low concentrations of compounds, in the low parts per million or even parts per billion,’ he added. ‘We have to be very careful not to lose them on the way to the sensors.’

Persaud hopes that a prototype will be ready within two years, and by the end of the three-year project the device should be ready to submit for regulatory approval.