Streptomyces sp., a cause of fistulous withers in donkeys

Four of 10 donkeys, which showed lesions simulating fistulous withers, were examined clinically with the aim to cultivate and identify the causal agent. Aspirated purulent materials were subjected to bacterioiogical examination. The causal organisms were recovered in Tryptic Soya agar medium when incubated aerobically at 37°C for up to 5 days. These organisms were found to be actinomycetes-like, Gram positive with stable branching filaments and to form heavy aerial hyphae on colony surface. The isolated organisms were tentatively identified as Streptomyces sp. on the basis of morphological and cultural characteristics. The initial sequence analysis of the 16S rDNA gene confirmed that one of the isolates (SD551) falls within the phylogenetic clade, which encompasses the genus Streptomyces. Studies are underway to further describe the disease and its causal agent. The report represents a good evidence to incriminate Streptomyces in the aetiology of the fistulous withers.