New, easy-to-adapt analytical procedure can quickly identify bacteria in hospitals

Soon in virtually every hospital it will be possible to identify the bacterial species responsible for an infection developing in a patient in a matter of just a few minutes. A new, easy-to-adapt and inexpensive analytical procedure has been developed by researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. The main role is played by innovative bioconjugates - luminescent, magnetic microparticles coated with appropriately selected bacteriophages.

When a patient is admitted to hospital with advanced bacterial infection, such as sepsis, time becomes crucial. The sooner it is possible to determine the species of the intruder ravaging the body, the greater the chance of successful treatment. Meanwhile, commonly used analytical methods still require the multiplication of bacteria (which often takes several days) or specialized equipment available in only a few laboratories. The identification of the bacteria can, however, be carried out in almost any hospital analysis laboratory and the waiting time for the result reduced to minutes, according to researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw in the pages of the respected scientific journal Bioconjugate Chemistry.

Before starting the work on the new analytical technique, researchers from the IPC PAS assumed that it should allow for significantly faster identification of bacteria than existing methods and be easy to introduce in a large number of hospital laboratories, but without any sacrifice of measurement accuracy. An additional requirement was that the analysis should be inexpensive.

"Faster, better, cheaper - we managed to achieve all of these objectives. This can be seen by any interested party as, in full awareness, we relinquished patent protection," says Dr. Jan Paczesny (IPC PAS), who led the research project funded by a grant from the Polish National Science Centre.

The detection device in the new technique for identifying bacteria is a flow cytometer. Despite the seemingly formidable name it is quite a simple and relatively inexpensive piece of equipment, available in many hospitals, where it is used commonly in blood tests. In the cytometer the sample is passed through a nozzle from which the stream that flows is so narrow that all the larger particles in the solution, particularly cells, have to flow one by one. The stream is lit by lasers and surrounded by detectors that record the light reflected from individual particles, scattered to the sides and emitted by them.

The main problem was to develop a method for labelling the bacteria to be easy to intercept them in the test sample and identify them with great certainty with the aid of the cytometer. To do this, researchers decided to construct special bioconjugates, i.e. complexes formed by the combination of microparticles with biomolecules. The biological element was a bacteriophage, which is a virus infecting a particular species of bacteria (the IPC PAS experimenters used the T4 bacteriophage, attacking Escherichia coli bacteria). The bacteriophages were coupled with microparticles capable of emitting light that could be easily registered on the cytometer and exhibiting magnetic properties. The latter was essential, because it made it possible to separate the bioconjugates from other particles in the sample with a simple magnet.

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