Molecular studies of metronidazole resistance development in Giardia intestinalis

Abstract: Giardia intestinalis is a two-staged flagellated protozoan parasite which infects the lumen of the small intestine causing the gastrointestinal disease called giardiasis. This disease infects millions of people per year, commonly caused by inadequate water treatment and proximity to livestock. The main line of treatment against this disease has been metronidazole, a member of the nitroimidazole family of prodrugs, which when activated cause non-specific damage to the proteins and genetic material within anaerobic cells. Until recently, G. intestinalis has shown little resistance to metronidazole, but as resistance climbs it has become clear that genetic regulation is key. This study attempts to investigate a select number of key genes through the use of modified transfected plasmids for overexpression and with knockdown using morpholino oligos. Wild type (WB) G. intestinalis cells, transfected with plasmids modified to both overexpress specific genes and incorporate the human influenza hemagglutinin tag (HA-tag) were seen to change in survival rate when exposed to metronidazole. Localization of a select group of these genes was also found using the HA-tag. Two of these genes (quinone oxidoreductase and nitroreductase 1) had protein folding simulations run in order to be visualizee and compare their structures to closely matching equivalents. Finally, morpholino oligo nucleotides were used to knockdown expression in these two genes, leading to a significant decrease in survival for those targeted against quinone oxidoreductase when exposed to metronidazole.