Sensitivity of Kinetoplastids to Aminoglycoside: Correlation with the 3’ Region of the Small Subunit rRNA Gene


Abstract: In vitro culture systems were used to assess the growth inhibition of kinetoplastids by a variety of aminoglycosides. The parasites were allowed to grow to the stationary phase in the presence of varying concentrations of the drugs. The IC-50 for every drug was calculated by comparison with the control. The sensitivity of various leishmanial strains to these drugs was in the order of: G418 > hygromycin > paromomycin > neomycin; however, under our assay conditions gentamycin and kanamycin were non-leishmanicidal. The effects of the drugs on the intracellular form of the parasite in the macrophage cell line were also tested. Other kinetoplastids, such as Crithidia spp., and Blastocrithidia culicis, were tested and showed resistance to all these drugs. Secondary structures for the 3´ region of the SSUrRNA genes for these organisms were constructed, and correlations between drug sensitivity and the secondary structures are presented. In Leishmania it is a T-A pair in the secondary structure instead of a C-G pair at position 1409-1491 (E. coli), as reported in other organisms, which is responsible for paromomycin sensitivity. The residue responsible for hygromycin sensitivity remained G(1494). The 3´ loop-stem U-structures are different for organisms in this family, which might be of significance in determining the overall sensitivity to these aminoglycosides. This might provide rational approaches to the development of drugs specific for Leishmania. Because of the sensitivity of mammalian cells to this drug, we suggest that paromomycin may be used for testing against leishmaniasis.

Keywords: Kinetoplastids, aminoglycosides, SSUrRNA, Leishmania

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