The present study reports on the location of major foci of footrot in goats in the Extremadura region of Spain by the determination of locally occurring strictly anaerobic microorganisms involved in the pathogenesis and development of this disease. The most commonly isolated microorganisms belonged to the genera Dichelobacter, Fusobacterium, Porphyromonas and Prevotella; these were found in conjunction with other species of minor importance. The species most frequently isolated were Fusobacterium necrophorum (40%), Dichelobacter nodosus (31.7%), Porphyromonas asaccharolytica (21.1%) and Prevotella melaninogenica (12.9%). Virulence factors identified in the isolated microorganisms included haemolysins, elastases and lecithinases, which enabled the organisms involved to initiate and/or aggravate the disease. Serotyping was performed for Dichelobacter nodosus isolates, since this species is responsible for triggering the process of infection. A and C were the most frequently isolated serovarieties (representing 40.7% and 25.9% of the cases, respectively).

The in vitro antimicrobial susceptibility of Gram-negative anaerobic bacilli commonly isolated from footrot in goats was studied. A total of 97 isolates belonging to the genera Dichelobacter, Fusobacterium, Prevotella, Porphyromonas and Bacteroides, obtained from clinical cases of footrot in south-western Spain between March 2000 and May 2001, were tested against 25 antimicrobial agents comprising β-lactams, aminoglycosides, macrolides, chloramphenicol, quinolones, lincosamides, sulphonamides and tetracyclines in order to optimise antibiotic treatment of this disease in goats. β-lactams, tetracyclines and metronidazole displayed the highest in vitro efficacy against the species involved in the pathogenesis of footrot.

Footrot is widely considered the most severe and most common foot pathology in small ruminants. This study tested the ability of a molecular typing system based on polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay of the 16S rRNA gene to discriminate between the strict anaerobe genera most commonly isolated from footrot (Bacteroides, Dichelobacter, Fusobacterium, Porphyromonas and Prevotella) in goats in Extremadura (Spain), with a view to facilitating identification for diagnostic purposes and thus providing a useful tool for future epidemiological studies. Although the electrophoretic patterns obtained with the enzyme Tru1I were more readily interpreted, and may thus be the best initial option, results may be confirmed by a second enzyme (RsaI). The PCR-RFLP assay of the 16S rRNA gene may therefore prove a useful addition to conventional biochemical identification techniques, providing taxonomic information at genus level.