Trichomonas vaginalis is a sexually transmitted human parasite causing trichomoniasis, leading to vaginitis or cervicitis in many patients. Furthermore, infections can lead to premature labour or loss of child as well as an increase in the risk of contracting HIV. For treatment the antibiotic 5-nitroimidazole metronidazole is commonly used, however antibiotic resistance in TV is on the rise, and the mechanism of how the parasite becomes resistant is not yet known. The aim of the study thus was to unravel the mechanism of resistance formation, by understanding the change in protein expression of the parasite. For this we studied different clinical isolates (i.e. various strains of TV) that were either sensitive or resistant to metronidazole, or resistance has been induced in a lab strain. It was previously known, that when sensitive TV cells are depleted of iron, they appear to have the same characteristics as resistant cell lines, however remained sensitive to the drug. Several proteins were identified, where the protein expression differed between the same cell line where either cells were depleted of iron, or resistance was induced. These proteins (mainly reductive agents) were studied on more detail. To understand the mechanism of metronidazole resistance.