Reduced Metronidazole Susceptibility in Trichomonas gallinae Strain Isolated from North of Iran

Objectives: Trichomonasgallinae, the causative agent of avian trichomoniasis is located in the upper digestive and respiratory tracts of a large variety of birds, mainly in the Columbiformes. The parasite has significant health and economic impacts on the poultry industry especially pigeons rearing and breeding. Nitroimidazoles are the drugs of choice for treatment of trichomoniasis. Subtherapeutic doses and preventive use of these drugs resulted in emergence of resistant strains of T. gallinae. Metronidazole resistant isolates of T. gallinae are reported from different parts of the world but till now there is no report on metronidazole susceptibility in T. gallinae isolated from Iranian pigeons. The present study aimed to evaluate in vitro metronidazole susceptibility of T. gallinae strain isolated from pigeons in north of Iran. Materilas Methods: T. gallinae was recovered by wet mount method from infected native pigeons. Smears were examined under a light microscope at ×400 magnification to confirm presence of T. gallinae. Parasite culture was prepared by immersing oral swabs intryptone/ yeast extract/ maltose (TYM) medium and incubated at 37ºC. To examine the susceptibility of T. gallinaeto metronidazole, sterile multi well plates were used. A volume of 100 µl of culture medium containing 1× 10^4 parasites pipetted into each well, as well as predilutedmetronidazole to give final concentrations of 1, 2, 5, 10, 20, 50, and 100 μg/ml. The wells were examined with an inverted microscope every 24 h for 3 competitive days. The MIC was the lowest concentration of the drug in the well at which no motile parasite was observed. All assays were done in triplicate and 24, 48 and 72 MIC values were measured.Results Conclusion: Results of the present study showed reduced metronidazole susceptibility in T. gallinaestrains isolated from north of Iran which can serve as serious threat endangering birds’ lives particularly birds of the wildlife.