Physiological aspects of nitro drug resistance in Giardia lamblia

• Published in: International journal for parasitology -- drugs and drug resistance Vol. 8; no. 2; pp. 271 - 277
• Main Authors: Müller, Joachim, Hemphill, Andrew, Müller, Norbert
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-08-2018; Elsevier
• Subjects: Adaptation; Anaerobiosis; Antiparasitic Agents - pharmacology; Antiprotozoal Agents - pharmacology; Diplomonads; Drug Resistance - physiology; Giardia lamblia - drug effects; Giardia lamblia - enzymology; Giardia lamblia - physiology; Giardia lamblia - ultrastructure; Giardiasis - drug therapy; Giardiasis - parasitology; Metronidazole - pharmacology; Nitro Compounds - metabolism; Nitro Compounds - pharmacology; Nitroreductases - metabolism; Oxidoreductases - metabolism; Oxidoreduction; Oxygen - metabolism; Thiazoles - pharmacology; Trophozoites - drug effects; Trophozoites - physiology; Trophozoites - ultrastructure; Anaerobiosis; MTZ; Diplomonads; NTZ; ALB; Oxidoreduction; Adaptation
• ISSN: 2211-3207; 2211-3207
• DOI: 10.1016/j.ijpddr.2018.04.008

For over 50 years, metronidazole and other nitro compounds such as nitazoxanide have been used as a therapy of choice against giardiasis and more and more frequently, resistance formation has been observed. Model systems allowing studies on biochemical aspects of resistance formation to nitro drugs are, however, scarce since resistant strains are often unstable in culture. In order to fill this gap, we have generated a stable metronidazole- and nitazoxanide-resistant Giardia lamblia WBC6 clone, the strain C4.
Previous studies on strain C4 and the corresponding wild-type strain WBC6 revealed marked differences in the transcriptomes of both strains. Here, we present a physiological comparison between trophozoites of both strains with respect to their ultrastructure, whole cell activities such as oxygen consumption and resazurin reduction assays, key enzyme activities, and several metabolic key parameters such as NAD(P)+/NAD(P)H and ADP/ATP ratios and FAD contents. We show that nitro compound-resistant C4 trophozoites exhibit lower nitroreductase activities, lower oxygen consumption and resazurin reduction rates, lower ornithine-carbamyl-transferase activity, reduced FAD and NADP(H) pool sizes and higher ADP/ATP ratios than wildtype trophozoites. The present results suggest that resistance formation against nitro compounds is correlated with metabolic adaptations resulting in a reduction of the activities of FAD-dependent oxidoreductases.
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•Physiological comparison between susceptible and nitro drug resistant Giardia lamblia trophozoites.•Resistant trophozoites exhibit lower nitroreductase activities, lower oxygen consumption and lower resazurin reduction rates.•Resistant trophozoites exhibit lower FAD and NADP(H) contents and higher ADP/ATP ratios.•Resistance formation against nitro compounds correlated with metabolic adaptations avoiding nitrosative and oxidative stress.