Use of Padlock Probes and Rolling Circle Amplification (RCA) for Rapid Identification of Trichophyton Species, Related to Human and Animal Disorder

Zakeri, Hamideh; Shokohi, Tahereh; Badali, Hamid; Mayahi, Saba; Didehdar, Mojtaba

The Trichophyton species were not easily differentiated from each other based on mycological criteria. Of the 61 clinically isolated samples, 31 isolates (50.8%) were identified as T. mentagrophytes var interdigitale, 11 isolates (18.2%) as T. rubrum, 9 isolates (14.7%) as T. tonsurans, and 1 isolate as (1.8%) T. violaceum. Moreover, 9 isolates (14.7%) were identified as non-Trichophyton species. RCA and subsequent detection by gel electrophoresis yielded positive results, and the test proved to be 100% specific for each species. Neither cross-reaction between the examined species of Trichophyton nor false positive or false negative results were observed (Figure 1 ). Positive RCA reactions were visualized by UV irradiation as ladder-like, strongly illuminated smears on 1.2% agarose gels, while the background remained clean for negative reactions (Figure 1 ). RCA reactions were performed for all isolates; 45 isolates (73.3%) were positive for the probe specific to T. mentagrophytes, 8 isolates (13.1%) for the probe specific to T. rubrum, and 4 isolates (6.6%) for the probe specific to T. tonsurans (Figure 1 ). However, four isolates (8.6%) did not test positive using any of the three species-specific padlock probes and probably represented separate dermatophyte species.