Identification of Dermatophilus congolensis From Colony Morphology Variants Resulting From Antimicrobial Pressures

Indianapolis, IN

Dermatophilus congolensis is the leading cause of Dermatophilosis, a disease found in a variety of mammals including horses, cattle, sheep, and polar bears. In a previous study by Hoke, presumed bacterial contaminants were found after photosensitization. This raised questions as to whether or not these contaminants were in fact D. congolensis colony morphology variants. The objectives of the current study were to repeat the past experiments by exposing D. congolensis to Rose Bengal and light to again generate the supposed contaminants. Each variant then underwent colony identification, gram staining, cellular morphology documentation, and biochemical testing. Finally DNA extraction was performed for genetic identification via PCR assay. There were varying results however; all variants were gram positive and had β-hemolytic activity on blood agar plates. The variation in other characteristics could be attributed to adaptation to antimicrobial pressures. From the micromorphology and PCR results of the current study it was concluded that the majority (5 of 7) of the isolates are morphological variants of Dermatophilus congolensis.