Exploiting intrinsinc fluorescence spectroscopy to discriminate Acinetobacter calcoaceticus- Acinetobacter baumannii complex species

Abstract

Several spectroscopic techniques, as infrared, Raman, fluorescence and/or mass spectrometry, have been tested in the context of bacterial typing being the degree of success highly dependent of the taxonomic level. Instrinsic fluorescence spectroscopy, due to the natural bacterial fluorophores, have been claimed to be a reliable alternative to the standard typing methods with some published works reporting its success. In this work we evaluate the ability of this technique to discriminate four closely related species belonging to the so-called Acinetobacter calcoaceticus Acinetobacter baumannii complex. Single-point and two dimensional fluorescence spectral data were acquired at room temperature and 25ºC. Spectra were analysed by partial least squares discriminant analysis and soft independent modelling of class analogy. The percentage of correct species assignments, ranging from 4.2 - 97.7%, is highly dependent of the experimental conditions and the data analysis. It seems that the results benefit from a strictly temperature control being those achieved with two-dimensional data slightly better. Nevertheless, it was impossible to achieve a satisfactory percentage of correct assignments for the four species simultaneously pointing to several limitations of this technique for such purposes.