The effects of metronidazole on sensitive and resistant strains of Trichomonas vaginalis : ultrastructural studies and minimum inhibitory concentration determinations
Kesling, Patricia F.
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Metronidazole sensitive and resistant strains of Trichomonas vaginalis were exposed to 1.4 μg/ml metronidazole for periods of 1, 3 and 6 hours and examined ultrastructurally. The metronidazole sensitive strain, after 1 hour exposure, showed an increased vacuolization resulting in the formation of large vacuoles containing numerous small vacuoles. Lysosomes became more oval in outline and exhibited a decrease in matrix density. Cisternae of the endoplasmic reticulum (ER) became distended and the cavity more electron translucent. Exposure of the sensitive organism to metronidazole for 3 hours resulted in an enhancement of these alterations as well as an increase in the granularity of the cytoplasm, the latter due to an increased deposition of glycogen and free ribosomes. The 6 hour exposure resulted in similar but considerably more enhanced alterations. The metronidazole resistant strain remained essentially unchanged when compared to untreated organisms after 1 and 3 hour exposures. The first discernable alteration, occurring after 6 hours of exposure, involved a widening of the ER cisternae and a decreased electron density of the cavity. An increase in the density of the cytoplasm was also noted due to an increased deposition of glycogen and free ribosomes. Morphometric analysis on the progression of vacuolization in the sensitive strain showed that the vacuoles initially increased in number and then became progressively larger in size with increased time exposure to metronidazole. Minimum Inhibitory Concentration (M.I.C.) levels also were obtained for each of the strains. Concentrations of 2 μg/ml and 6 μg/ml were shown to be the M.I.C. levels for the sensitive and resistant strain, respectively. The ultrastructurally discernable alterations in regard to induced matabolic changes within Trichomonas vaginalis were found to be consistent with both the results of previous investigators and the proposed mode of action of metronidazole.