Military Could Use Hand-Held Spectroscopy for Pathogen Detection

It is feasible to use surface-enhanced Raman spectroscopy (SERS) for the detection of microorganisms. Further, the use of the technology to generate a "molecular fingerprint" of infection-causing pathogens is potentially clinically "valuable" to either prevent or more effectively treat high rates of wound infections in military personnel, according to a military technical report.

Current diagnostic assays used to identify the infection-causing pathogen and select appropriate treatment are limited in their sensitivity and take too long due to the need to isolate and culture bacteria. While molecular approaches have aided pathogen identification in traditional settings, they are not yet point-of-care field deployable. Researchers from the Naval Medical Research Unit-San Antonio (NAMRU-SA; Ft. Sam Houston, Texas) believe that SERS could meet a critical unmet need for rapid, sensitive diagnosis, even in field conditions.

The NAMRU-SA scientists recently demonstrated that the SERS device could identify five bacterial species from pure culture and bacteria recovered from human serum using a proprietary lysis filtration procedure. The technique was utilized on 16 bacterial isolates. Quantitative polymerase chain reaction with melting curves was used to validate the SERS spectra. The spectra (or fingerprints) demonstrate shifts in the frequency of a fixed light as a result of structures in the bacterial cell wall. Libraries of bacterial SERS spectra can serve as a reference. A hand-held SERS biosensor system could not only generate unique "molecular fingerprints" for these organisms in under 30 seconds, but it could also discriminate between bacterial species. Additionally, mixtures of gram-negative and gram-positive bacterial species can be differentiated from either species alone.

The researchers believe the SERS biosensor will be able to aid caregivers in selecting appropriate antibiotic treatments. They say that after successful identification of an infecting microbe, drug resistance can be evaluated by observing shifts in SERS peak intensity after incubation on antibiotic coated nanoparticles. John Simecek, D.D.S., from NAMRU-SA, tells DTET that the group is working on additional refinements with a particular emphasis on improving the methods of isolation during sample preparation. This will increase bacterial extraction yields, reduce component equipment requirements, and cut total time from sample receipt to pathogen detection.

"The data demonstrate that SERS can be used to accurately discriminate between bacterial species in a quick and efficient manner," writes lead author Rene Alvarez, Ph.D., in the technical report. "This report sets the foundation for the utilization of a SERS platform for rapid detection of microorganisms of military relevance, which may ultimately lead to the development of a field deployable point-of-care handheld detection system."

Takeaway: Hand-held development of SERS technology could transform care for wound treatment in combat-injured military personnel and may ultimately have civilian applications at the bedside or clinic.