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Abstract

Introduction: Current identification and antibiotic resistance profiling techniques for Staphylococcus aureus (S. aureus) are slow, requiring the use of broad spectrum, expensive antibiotics while waiting for cultures to return. In addition, tests to detect isolates with reduced susceptibility to vancomycin are often not performed. Raman Spectroscopy uses near infrared light to develop a spectral pattern that is unique to a specimen. This can be advantageous in bacterial identification in that it is quick, and can be used for real-time assessment. Hypothesis: The purpose of this study was to determine the ability of Raman Spectroscopy to identify S. aureus, as well as its antibiotic susceptibilities. Methods: Raman Spectroscopy was applied to samples of S. aureus to obtain spectral patterns. One hundred-twenty spectra were obtained from 4 different strains of S. aureus – 2 sensitive to methicillin (MSSA), 1 resistant to methicillin (MRSA), and 1 strain of MRSA with reduced susceptibility to vancomycin (RVS-MRSA). The spectra were pre-processed using BacLearner software, and analyzed with SPSS(r) Statistics 19. Results: Raman Spectroscopy can correctly distinguish between strains of S. Aureus with 83% accuracy. However, Raman Spectroscopy can correctly classify a specimen as MRSA vs. MSSA with 90.2% accuracy, with a sensitivity of 96% and specificity of 85%. RVS-MRSA vs. MRSA was correctly classified with 96.3% accuracy, with a sensitivity of 100% and specificity of 93%, while RVS-MRSA vs. MSSA was correctly classified with 96.5% accuracy, with a sensitivity of 100% and specificity of 94.8%. Test-train analysis was performed to train the program to classify new samples according to a pre-formed model, with 98% accuracy for MRSA vs. MSSA, and 98% accuracy for RVS-MRSA vs. MRSA. Conclusions: Raman Spectroscopy is a reliable method for identifying and determining antibiotic resistance of S. aureus strains. This method can have broad applicability for fast and easy detection, as well as appropriate antibiotic selection, for the initial treatment of S. aureus infections.