Dermatophilus congolensis infection in sheep and goats in Delta region of Tamil Nadu
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Date
2017-11
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Abstract
Aim: The study was conducted to isolate and identify Dermatophilus congolensis (DC) using conventional and molecular
diagnostic techniques in scab materials collected from skin infections of sheep and goats in the Delta region of Tamil Nadu.
Materials and Methods: A total of 20 scab samples collected from 18 goats and 2 sheep from Nagapattinam, Thanjavur, and
Tiruvarur districts of Tamil Nadu. Smears were made from softened scab materials and stained by either Gram’s or Giemsa
staining. Isolation was attempted on blood agar plates, and colonies were stained by Gram’s staining for morphological
identification. Identification was also done by biochemical tests and confirmed by 16S rRNA polymerase chain reaction
(PCR), followed by sequencing and phylogenetic analysis of the amplified product.
Results: The peculiar laddering arrangement of coccoid forms in stained smears prepared from scab materials revealed the
presence of DC. Isolated colonies from scab materials of sheep and goats on bovine blood agar plate were small, hemolytic,
rough, adherent, and bright orange-yellow in color, but some colonies were white to cream color. Gram-staining of cultured
organisms revealed Gram-positive branching filaments with various disintegration stages of organisms. 16S rRNA PCR
yielded 500 bp amplicon specific for DC. Sequence analysis of a sheep DC isolate showed 99-100% sequence homology
with other DC isolates available in NCBI database, and phylogenetic tree showed a close cluster with DC isolates of Congo,
Nigeria, and Angola of Africa. Genes for virulence factors such as serine protease and alkaline ceramidase could not be
detected by PCR in any of the DC strains isolated of this study.
Conclusion: The presence of dermatophilosis in Tamil Nadu was established from this study.
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Keywords
Veterinary Science, Veterinary Microbiology