Journal articles made easy: Detecting strep throat using mass spectrometry
Type of Activity
Detecting strep throat bacterium using touch spray mass spectrometry
Additional information from the authors
Information on the authors
Alan Jarmusch, one of the authors, answers some additional questions on his group's work.
Could you please summarise how Strep throat is currently diagnosed and explain how the system you have developed is better than those that are already available?
Strep throat is primarily diagnosed using a patient’s clinical symptoms but nearly always aided by rapid tests performed during a visit to the physician. The rapid tests (called rapid antigen detection tests – RADT) are necessary in diagnosing strep throat as the common symptoms (sore throat, fever, etc) are not unique to only strep throat. The rapid test takes about 15-20 minutes, depending on the commercial product, and gives a visual indication of the test result – similar to an at-house pregnancy test.
Our methodology aims to address gaps and expand capability, (1) we hope to match or improve diagnosis when a patient has an infection (true positive) while improving on the false negative rate, thereby improving patient care. One way we accomplish this is by using many biomolecules (specifically lipids - they are part of all bacteria cells (and our cells as well)) which are detected simultaneously and used in combination for diagnosis. (2) Our hypothesis is that (in specific circumstances) the lipids detected from bacteria allow for them to be distinguished. We hope to answer to the question, “what (if any) bacteria is present?” which should allow physicians to better treat patients.
How did the idea for the design of your system come about? What was the inspiration behind the study?
The idea originated during development of touch spray ionization which was itself motivated by a need for cancer diagnosis during tumor removal operations. The original probe used in those experiments was metallic and sharp, not practical for use in strep throat diagnosis – it was too harsh for someone’s throat. With the idea of translating touch spray ionization into a non-invasive procedure that patients could withstand in the doctor’s office we started experimenting with swabs.
The inspiration is quite personal to the author, Alan Jarmusch, who was afflicted with strep throat as a child (like many); however, his case progressed beyond most. A fairly minor case of rheumatic fever, left the author unable to walk and subjected to a sting of doctor visits and antibiotic regiments.
Could you briefly explain in simple terms how your system works. How do you get from a throat swab to a read out of whether or not you have Strep throat?
The simple answer is that we are detecting the molecules from bacteria directly from the throat swab. Mass spectrometry, the method of detection, requires ions, our methodology generates ions directly from the swab.
The read out of our mass spectrometry method is complex in its unrefined form called a spectrum (spectra plural), containing peaks which correspond to one or more ions. Currently, the read out relies only on visual pattern recognition. However, future development will include a method to automatically recognize the peaks and provide an easily read output – could be as simple as red-light, “you have strep throat” or green-light, “you do not have strep throat.”
Could you describe any problems you had during this research. Which part of the work towards this paper proved to be most challenging and how did you overcome the problems that you faced?
One major obstacle was adapting a medical device (swab) for mass spectrometry, something it was not intended. The shape and materials of the swab were critical in how well it performed this specific task. A number of different swabs were tested and the best one was pursued. The performance of the swab for MS could certainly be improved by small changes in materials and manufacturing.
How can you see the system that you have developed being used in the future? Do you expect that your system will one day become commercially available? What needs to be done before this can be achieved? What other uses do you see for your system?
The prospective application would be for point-of-care (in the physician’s office) diagnosis of strep throat and additional diseases that are tested using swabs. The increasing development of miniature mass spectrometers will certainly aid in this development allowing laboratory scale instruments, too large for most doctor’s offices, to be adapted into compact clinical instruments.
We hope that this system would become commercially available after some critical development steps. Work needs to be done to extend our method to true clinical samples, improving the methodology further, and eventually comparing our method to that or current methods. The extension of this method to additional bacteria is foreseeable as well as other common medical test that would benefit patient care done at the point-of-care.
What are the limitations of the technique you have developed? What is the next step to overcome these limitations?
Many of the limitations stem from the inexperience in using medical devices for mass spectrometry, they are not created for such a purpose and are only a number of previous examples. Overcoming the limitations should be a matter of developing a mass spectrometry-friendly swab. Another limitation is the high initial cost of a mass spectrometer and the expertise need to run such an instrument; however, future full-size and miniature mass spectrometers are likely to address these issues.
What are your plans now? What are you doing at the moment and what will you be working on in the near future?
We are planning to develop the method so that is more rigorous, extend the methodology to incorporate additional bacteria, and test our methods using real clinical samples.