Novel Technique Helps Surgeons Identify Bacteria

A faster, less expensive method has been developed for identifying bacterial infections and determining their antibiotic resistance.

The technology known as Raman spectroscopy looks at the bacteria's infrared wavelengths and pinpoint unique patterns of molecular vibration in blood samples.

Surgeons at the Detroit Medical Center at Wayne State University (Detroit, MI, USA) observed 120 spectral patterns from four strains of antibiotic resistant Staphylococcus aureus: two that were sensitive to the antibiotic methicillin, one that was resistant to methicillin and a more stubborn form of Staphylococcus infection that has a reduced susceptibility to a last-resort antibiotic called vancomycin (RVS-MRSA).

Raman spectroscopy enabled the scientists to distinguish the methicillin, sensitive S. aureus (MSSA) from methicillin resistant S. aureus (MRSA) with 90.2% accuracy. They also could tell the difference between MRSA and its more stubborn form, RVS-MRSA, with 96.3% accuracy. The S. aureus profiles were then entered into a statistical program to create a preformed model of the Raman spectra. When the surgeons tested new spectra, the program was 98% accurate in classifying the bacteria as one of the four strains.

The S. aureus profiles generated by Raman spectroscopy are among dozens of pathogen profiles being added to a database of other bacteria, viruses, malignant tumors, and fungi. The team is simultaneously developing a technology to integrate the pathogen database and the Raman spectroscopy technique into a hand-held device that would cut turnaround times for diagnostic test results from several hours to about 10 minutes.

Amy Riley Spencer, MD, who led the study said, "Currently, emergency room patients may have to wait about six hours before diagnostic tests can identify a Staphylococcus infection and another 24 to 72 hours to determine which antibiotics could treat it. Our findings suggest that Raman spectroscopy can identify the infection earlier and save money by treating the infection quicker instead of hoping an antibiotic is working and then switching when it does not."

The findings were reported on October 26, 2011 at the 2011 Annual Clinical Congress of the American College of Surgeons, held in San Francisco (CA, USA).

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