title: Phenotypic and transcriptional profiling in Entamoeba histolytica reveal costs to fitness and adaptive responses associated with metronidazole resistance.
abstract: Antimicrobial chemotherapy is critical in the fight against infectious diseases caused by Entamoeba histolytica. Among the drugs available for the treatment of amebiasis, metronidazole (MTZ) is considered the drug of choice. Recently, in vitro studies have described MTZ resistance and the potential mechanisms involved. Costs to fitness and adaptive responses associated with resistance, however, have not been investigated. In this study we generated an HM-1 derived strain resistant to 12 μM MTZ (MTZR). We examined its phenotypic and transcriptional profile to determine the consequences and mRNA level changes associated with MTZ resistance. Our results indicated increased cell size and granularity, and decreased rates in cell division, adhesion, phagocytosis, cytopathogenicity, and glucose consumption. Transcriptome analysis revealed 142 differentially expressed genes in MTZR. In contrast to other MTZ resistant parasites, MTZR did not down-regulate pyruvate:ferredoxin oxidoreductase, but showed increased expression of genes for a hypothetical protein (HP1) and several iron-sulfur flavoproteins, and downregulation of genes for leucine-rich proteins. Fisher's exact test showed 24 significantly enriched GO terms in MTZR, and a 3-way comparison of modulated genes in MTZR against those of MTZR cultured without MTZ and HM-1 cultured with MTZ, showed that 88 genes were specific to MTZR. Overall, our findings suggested that MTZ resistance is associated with specific transcriptional changes and decreased parasite virulence.
authors.affiliation: Department of Parasitology, National Institute of Infectious Diseases Tokyo, Japan ; Department of Parasitology, Gunma University Graduate School of Medicine Maebashi, Japan.
authors.forename: Gil M
authors.initials: GM
authors.lastname: Penuliar
authors.affiliation: Department of Parasitology, National Institute of Infectious Diseases Tokyo, Japan.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Nakada-Tsukui
authors.affiliation: Department of Parasitology, National Institute of Infectious Diseases Tokyo, Japan ; Graduate School of Life and Environmental Sciences, University of Tsukuba Tsukuba, Japan.
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Nozaki
keywords: Entamoeba histolytica; drug resistance; metronidazole; transcriptome