Isolation of Crithidia spp. from lesions of immunocompetent patients with suspected cutaneous leishmaniasis in Iran.

Leishmania major has been considered as the main aetiological agent of cutaneous leishmaniasis in Iran. However, there are recent reports about the existence of Crithidia spp in cutaneous lesions in southern Iran. Therefore, this study was designed to decipher some morphological, biological and molecular aspects of this phenomenon. Clinical isolates were obtained from 167 patients with cutaneous ulcers. A set of specific primers based on GAPDH (Glyceraldehyde-3-Phosphate Dehydrogenase) gene were used to distinguish between Crithidia and Leishmania genera. For molecular analysis, Pulsed Field Gel Electrophoresis and Mi-Seq Illumina platform were applied. Then, morphological analysis and some biological features (including potential growth at 37 °C and the ability of infecting mammalian macrophages) were studied. In 92.8% of clinical cases, L. major was the only causative microorganism isolated; in 5.4% of cases, co-infection of L. major and Crithidia spp. was identified; and in 1.8% of lesions, only Crithidia spp. were found. We isolated Crithidia spp. from clinical samples of patients suspected of cutaneous leishmaniasis in Iran, indicating that Crithidia spp. are capable of surviving at human body temperature and infecting macrophage cells. This raises questions on the influence of this phenomenon on pathogenicity, therapeutic outcome and disease control strategies.