Assessing Drug Action in Giardia Using Hyperspectral Raman Imaging*

This study demonstrates that Raman microscopy can detect structural changes in Giardia cells under various drug treatments. Each drug acts via distinct mechanisms: oseltamivir (OSM) alters lipid and phenylalanine structures, whereas metronidazole (MTZ) triggers the release of extracellular vesicles containing toxic iron intermediates and modified triple bond moieties. While both drugs affect the heme protein environment and the conversion of ferric to ferrous iron, more pronounced changes are observed for MTZ. The MTZ-induced vesicles evolve over time, initially containing altered proteins, glycogen, and phospholipids, and later forming agglomerates of iron complexes and multi-bond structures. In contrast, OSM does not induce vesicle release but disrupts the plasma membrane and lipid raft dynamics, as confirmed by confocal fluorescence microscopy, consistent with Raman observations. By enabling label-free, simultaneous monitoring of structural changes at cellular and molecular levels, Raman microscopy provides insight into the complex mechanisms of giardiasis treatment and drug resistance.