Abstract

Many infective agents are implicated as causal agents of mastitis. Miscellaneous causes of mastitis in bovine due to actinomycetes such as nocardiae have been described but neither Rhodococcus nor Dietzia species have been reported. The aim of this study was to report the isolation and characterization of rhodococcus-like actinomycetes as causal agents of mastitis in cattle. Milk samples (n = 100) collected from cattle suffering from mastitis in Sudan were subjected to microscopic examination using modified Ziehl Neelsen stains and cultured on Trpytic Soya agar medium. Out of the 100 milk samples collected from cattle suffering from mastitis in Sudan, five (5%) revealed rhodococcus-like growth which showed gram-positive coccobacilli. Two of the five samples showed partially acid-fast coccobacilli when milk samples were directly stained with modified Ziehl Neelsen method. The isolates were tentatively identified as members of the genusRhodococcus on the basis of morphological, biochemical and mycolic acids pattern. Comparative analysis of the 16S rDNA gene sequence confirmed that the strains fall within the phylogenetic branch which accommodates members of the genus Dietzia, but well separated from the validly described Dietzia spp. The isolation of 5% Dietzia sp. could represent a new significant cause of clinical mastitis in cattle.

Key words: Actinomycetes, nocardioform, Dietzia, Sudan, mastitis, cattle.