Raman Spectroscopic Characterization of Packaged L. pneumophila Strains Expelled by T. thermophila

The intracellular lifestyle of L. pneumophila within protozoa is considered to be a fundamental process that supportsits survival in nature. However, after ingesting the cells of L. pneumophila some protozoa expel them as compressed live cells inthe form of small rounded pellets. The pellets of tightly packed viable but not culturable forms (VBNCFs) as well as highly infectiousmature intracellular forms (MIFs) of L. pneumophila are considered as infectious particles most likely capable to cause humaninfection. Since L. pneumophila cells are hardly culturable from these pellets, detection methods for packaged live L. pneumophilaforms remaining in water should be cultivation free. Hence, we demonstrate the potential of Raman microspectroscopy to directlysort pellets containing L. pneumophila cells, expelled by T. thermophila, and to characterize them based on their Raman spectra.