In vivo and in vitro sensitivity of Trichomonas gallinae to some nitroimidazole drugs.

A study was carried out in order to establish the in vivo efficacy of two nitroimidazole drugs against the flagellate Trichomonas gallinae. The results obtained showed a high proportion of therapeutic failures. Thus, carnidazole and dimetridazole failed to eliminate infection in 13 of 17 and 20 of 21 racing pigeons, respectively. The in vitro susceptibility of four T. gallinae isolates to five nitroimidazolic drugs, that is, carnidazole, dimetridazole, metronidazole, ornidazole and ronidazole, was also determined. Minimal lethal concentrations (MLCs) of these drugs were obtained. One of the isolates tested had already proved to be resistant in the first in vivo tests, while the other three had been obtained from wild birds. We were able to confirm in vitro the resistance of the racing pigeon isolate to all the nitroimidazole drugs tested. For carnidazole, dimetridazole, metronidazole and ornidazole the MLC ranged between 93.75-500 microg ml. Although ronidazole showed a greater potency than the other nitroimidazole derivatives against this isolate (MLC: 15.62-31.25 microg ml), 8-22 times more drug was necessary for efficacy against this isolate compared to the others. These other three parasite isolates proved to be sensitive to the five drugs tested (MLC: 0.97-7.81 microg ml).