Isolation and identification of Dichelobacter nodosus and Fusobacterium necrophorum using the polymerase chain reaction method in sheep with footrot

Footrot is an important infectious disease of small ruminants leading to severe economical losses. The aim of the present study was to determine isolation and identification rates of Dichelobacter nodosus and Fusobacterium necrophorum in the culture techniques and reveal the specificity and sensitivity of the culture technique based on the polymerase chain reaction (PCR) method in sheep with footrot. Dry swabs and swabs with Amies medium from 83 sheep were subjected to PCR and culture analyses. In dry swabs, 4 samples were positive for F. necrophorum and all were negative for D. nodosus . Colonies in Eugon and Fusobacterium selective agars from swabs with Amies medium were evaluated. Polymerase chain reaction analysis was conducted on macroscopically and microscopically unidentified samples. The positivity rate was 55.4% for D. nodosus and 69.8% for F. necrophorum in cultures from Fusobacterium selective agars. The positivity rate for D. nodosus in Fusobacterium selective agars was higher than that in Eugon agar. Performing PCR and culture methods increased positivity as compared to performing them alone. In comparison with the PCR method, culturing in Fusobacterium selective agars had moderate sensitivity and low specificity for D. nodosus (71.7 and 28.7%) and F. necrophorum (61.3 and 80.0%), respectively. In conclusion, Fusobacterium selective agar (without antibiotics) for isolation and identification of D. nodosus is superior to Eugon agar. Fusobacterium necrophorum should also be considered as a provoking agent for footrot in small ruminants. The PCR method on culture increases elucidation of definitive aetiology.