Label-free Raman spectrometric detection and differentiation between Bacteria Staphylococcus Aureus and Neisseria Gonorrhoeae

Staphylococcus aureus and Neisseria gonorrhoeae are two important human pathogens that are associated with multi-drug resistance. Developing a method for rapid detection and differentiation between the antibiotic resistant and responsive bacterial strains is paramount. This will enable subscription of the correct drug thus curbing antibiotic resistance. In this work, Raman spectroscopy was explored, first, in detecting and differentiating between Staphylococcus aureus and Neisseria gonorrhoeae bacteria strains. Secondly, it was used in distinguishing between drug-resistant (antibiotic resistant) and drug-responsive Staphylococcus aureus bacterial strains. Raman sample substrates were prepared by smearing conductive silver paste onto a microscope glass slide. Samples were applied onto the smear and excited with a 785 nm laser and the Stokes Raman signals recorded and analyzed. Distinct biomarker Raman bands for the two bacterial species ( Staphylococcus aureus and Neisseria gonorrhoeae ) were identified by analyzing band intensities using Principal Component Analysis (PCA) and Analysis of Variance (ANOVA). The bands exhibiting significant intensity variation were those centered around wavenumbers 800 cm −1 , 846 cm −1 and 1028 cm −1 for Staphylococcus aureus ; 635 cm −1 , 710 cm −1 , 941 cm −1 ,1232 cm −1 and 1307 cm −1 for Neisseria gonorrhoeae . These bands could act as biomarker Raman bands for detecting the two bacteria species. Besides the bands identified for drug-responsive Staphylococcus aureus, characteristic bands for the drug-resistant variant were observed around wavenumbers 720 cm −1 , 1320 cm −1 and 1440 cm −1 . The tentative vibrational assignments of these bands were: C N stretch (800 cm −1 ), ring breathing (846 cm −1 ), C C ring breathing (1028 cm −1 ), aromatic ring skeletal (635 cm −1 ), CH 2 rocking (710, 720 cm −1 ), C N ring (941, 950 cm −1 ), and NH 2 ring (1232, 1307, 1320 cm −1 ). The results reported here demonstrate a potential utility of Raman spectroscopic method in rapid (<1 min), label-free and low-cost detection and differentiation between drug-responsive and drug-resistant bacterial strains.