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Rapid methods for detecting bacteria at the bedside

Published: Fri 27 Nov 2015
Rapid methods for detecting bacteria at the bedside

Professor Stephen Rimmer, Head of School of Chemistry and Forensic Sciences.

Over use of antibiotics is probably the biggest heath issue facing the world in the 21st century.

Failure to address the problem will lead to a post antibiotic era in which people die of common ailments such as tooth decay and serious diseases such as TB will range unchecked. A key requirement for better control of antibiotics is providing faster and greater information to clinicians.

At the moment too much time is lost while laboratories work on infected samples obtained from swabbing and the central technique is to grow bacteria in the laboratory. Trained staff then use their skills to identify the type of bacteria using microscopy but other laboratory techniques such as staining are used as well. All of this takes time and for the seriously ill this is time that cannot be wasted. The result is that antibiotics have to be prescribed with only symptom level knowledge of the patient’s condition. Of course a microbiology laboratory may not be available anyway and this is especially the situation in the developing regions such as rural India. So there is a growing realisation that technologies that can be used to rapidly analyse samples from infected tissues in the clinic would provide the vital information that a clinician needs, hopefully in a much shorter timeframe than the current laboratory based culture methods. What is required are devices and materials that can provide both indications of the presence of bacteria and some level of identification. A good step forward would to have a system that can distinguish between the two main classes of bacteria: Gram –positive or Gram-negative.

Our multi-national team of scientists and clinicians including chemists at the University of Bradford, Biologists at the University of Sheffield and clinicians and scientists at the LV Prasad Institute and University of Hyderabad, India are developing advanced polymers that can disclose the two classes bacteria work is currently funded by both the Wellcome Trust, the MRC and DBT. We have also just completed a productive research programme in the area with global healthcare corporation Smith and Nephew. Much of the work is aimed at providing simple to use devices that can provide indications of infection within one hour and although much remains to be done considerable progress is being made that will be of major benefit to clinicians attempting to prescribe the correct and optimum treatments.

One of the advantages of this system is that it can be fabricated into many different types of device. This means that systems appropriate to most disease states can be developed. Much of the current work is aimed at infections in eyes and our estimates are that a successful adoption in India could save around 50% of eyes that are currently lost.

The system builds on some ground breaking observations made by us in the over the last 20 years. We were the first to show that a synthetic polymer could respond to the presence of bacteria and critically whether the polymer responds or not depends on its design. Using a synthetic polymer we can design polymers that only respond to Gram-positive bacteria and others that respond only to Gram-negative bacteria. It should also be possible, with a good deal of further research, to develop specific systems for particular species or even strains. Obviously we would very much like to be able to different between normal strains and multiple resistant strains such as MRSA. However, we need first to probe the detail of the biochemistry of targets such as MRSA because we need specific sites on the bacteria that are unique to that strain and then we will need to develop a polymer that binds only to these features. None-the-less with enough effort it should be possible to do this.

Simply differentiating between Gram-positive and Gram-negative provides very powerful information to the clinician, who armed with this information, can select appropriate antibiotics. This can have a big impact in the fight against resistance developing bacteria.

*The polymer system is a branched water soluble polymer (poly(N-isopropyl acrylamide) with groups that bind to bacteria at the chain ends. When the ends bind to the bacteria water is lost from polymer and it shrinks from an open coil to a collapsed globule. Detection of the bacteria relies on methods that can detect the change from open coil to collapsed globule.

Prof Stephen Rimmer, Head of Chemistry and Forensic Sciences reacting to BBC News article.

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