Molecular Study of Recovered Dermatophilus congolensis DNA from Archival Eosin-stained and Gram-stained Slides

ackground: Dermatophilosis is a significant livestock disease and a zoonotic agent of economic importance. Dermatophilosis is an exudative, pustular dermatitis of animals. The disease has been reported worldwide, with a broad host range that includes domestic, wild and aquatic animals. Humidity and ticks are predisposing factors. The principal causative agent is Dermatophilus congolensis. Objectives: This study investigated the reliability of using stained slides for DNA amplification. Genetic detection of the Dermatophilus species by molecular methods and comparison of the detected genome to the entire National Center for Biotechnology Information (NCBI) gene bank to detect the percentage of similarity of D. congolensis and other related class microorganisms. Materials and Methods: In May 2002, samples were collected from 3 out of 55 goats from Awdalok Village, Koysinjaq District, Erbil Governorate, Iraq. The diagnostic slides, which had been well preserved since then, were used in this study. This study was performed in 2015. The DNA was extracted from the slides using a modified Motazedian procedure. Polymerase chain reaction (PCR) amplification is performed using primers specifically designed for the 16S rRNA gene. Sanger sequencing and gene bioinformatics were used to confirm the genus and species of the D. congolensis. Results: Four of the five slides gave positive PCR results for amplification of the 16S rRNA gene. The PCR product was 470 bp in size. Sanger sequencing was done for the positive samples. The sequenced data were successfully deposited in the NCBI site. Conclusion: The 16S rRNA gene is a highly conserved gene that can be used for the diagnosis of microorganisms. The scraped material from stained slides could be used for diagnosis. DNA sequencing is the most accurate method for species detection, especially when multiple genera within the same class share genomic similarities.