Mass spectrometry technique could speed up UTI treatment

Researchers using a new method for identifying bacteria claim it will lead to faster, cheaper and more effective urinary tract infection (UTI) treatment.

Scientists at University Hospital Essen in Germany have been able to separate and identify bacteria in urine using a type of mass spectrometry in 30 minutes — much quicker than the traditional biochemical methods that typically take 12 hours or more.

The Matrix-Assisted Laser Desorption Ionisation-Time of Flight (MALDI-TOF) technique is also unaffected by any antibiotics the patient may have taken and the bacteria sample doesn’t need to be cultured before testing.

‘Identifying bacteria quickly and accurately using MALDI-TOF means treatment for UTIs can be started at an early stage and with an antibiotic targeted at the correct bacterial culprit,’ said research leader Dr Frank Mosel.

‘This should mean less patient suffering, fewer complications and a reduction in the costs of both diagnosis and therapy. What’s more, the sensitivity of the test is nearly 100 times higher than the minimum clinical threshold for UTI diagnosis.

‘This means that developing infections can be identified in routine urine samples before clinical symptoms appear. This is particularly helpful for catheterised hospital patients who may have weakened immune systems and may therefore be more susceptible to infection.’

The technique involves measuring the speed at which particles of a biological sample travel when pulses of UV light are fired at it. From this, scientists can calculate the mass and so the identity of each molecule.

When the light hits the particles, they all become either positively or negatively charged and are then forced down a tunnel by an electrical force. Because the particles have the same charge, their speed is dependent on their mass.

The study, published in Journal of Medical Microbiology, also revealed some limitations of MALDI-TOF in identifying bacteria.

‘Bacteria in urine samples from patients who had undergone surgery for lower urinary tract (e.g. bladder) cancers could not be detected. The human proteins produced interfere with the urine analysis, causing detection problems,’ said researcher Hedda Köhling.

Mosel believes that the use of MALDI-TOF mass spectrometry could be extended more widely as a medical analysis tool.

‘This method could quite feasibly be extended to blood, cerebrospinal fluid and other bodily fluids to detect bacteria or even fungi,’ he said.

‘One of the big advantages is that every sample can be processed independently without any prior assumptions about what microbes will be found.’