Utilization of laser induced fluorescence for the discrimination between two bacterial strains

The present work reports on the evaluation of laser induced fluorescence (LIF) for the discrimination between different microbial strains. Pseudomonas aeruginosa and Staphylococcus aureus are important pathogenic bacteria for which therapeutic options are lacking nowadays. These microbial strains were selected due to their medical relevance as they are commonly found in human diseases infections. LIF is a spectrochemical analytical technique that was used in the present study to obtain bacteria spectral fingerprints in the liquid phase. Two laser wavelengths, 266 nm (UV) and 405 nm (violet), have been used as excitation light sources delivering output power 5 mW and 100 mW, respectively. The results of LIF analysis showed that the differences in fluorescence bands intensity can be used as a fingerprint for each bacterial species. In addition, the fluorescence emission intensities of the two strains were exponentially related to the concentration of the bacteria. Confocal laser scanning microscopy was used successfully to visualize the fluorescence emission of the cells in comparison with the LIF measurements. The obtained results demonstrate the potential of LIF as a fast, noninvasive, and easy technique for bacterial discrimination. The technique can be also used for the determination of bacteria concentration after performing proper calibration.