Monitoring the identity of bacteria using their intrinsic fluorescence

Three different fluorescence spectra were recorded following excitation at 250 nm (aromatic amino acids+nucleic acids), 270 nm (tryptophan residues) and 316 nm (NADH) for 25 strains of bacteria in dilute suspensions. Evaluation of the spectra using principal component analysis and hierarchical clustering showed a good reproducibility from culture to culture and a good discrimination of the bacteria. Applying the method of Mahalanobis distances to the spectra of lactobacilli species recorded following excitation at 250 nm, a good classification was observed for 100% and 81% of calibration and validation groups, respectively. The developed method allows the discrimination and identification of the investigated bacteria at the genus, species and strain levels.