A summary of major virulence factors of F. nodosus may have importance as a source of alternative fimbrial antigens. The anaerobic, gram negative, nonsporing and non-motile bacilli, ranging from. Such events would explain some of the difficulties encountered in control of footrot by vaccination and suggest that benign strains of D. (a) Facultative anaerobes - Can grow in the presence or absence of oxygen. It has been suggested that serogroup conversion, possibly due to recombination following natural transformation, may occur in the field ( Kennan et al. The fimA gene is essential for virulence in sheep and antigenic diversity of the fimbriae is based on variation in the carboxy-terminal of this gene. nodosus may be classified as virulent, benign or of intermediate virulence according to the clinical lesions and proteases produced. The fimbriae are highly immunogenic and are classified into 10 major serogroups, designated A to I and M. Virulence of Dichelobacter nodosus, the primary causal agent in footrot of sheep, is dependent on the presence of Type IV fimbriae and the production of proteases (Kennan et al. Other important virulence attributes include the production of high levels of endotoxin, haemagglutinin production, and dermotoxic activity which may be due to a collagenolytic cell wall component ( Okamoto et al. This toxin, encoded by the gene lktA, is particularly effective against ruminant leukocytes and induces activation and apoptosis of these cells ( Narayanan et al. Phosphatase activity of aerobic and facultative anaerobic bacteria. Its major virulence factor is a leukotoxin. The subgingival prevalence of gram-negative facultative rods not usually inhabiting. are described in Chapter 31 and Actinomyces bovis and Actinobaculum suis in Chapter 10.ĭiseases caused by non-spore-forming anaerobesįusobacterium necrophorum is a normal inhabitant of the gastrointestinal tract and is a major cause of necrobacillosis in animals, particularly calf diphtheria, liver abscesses in cattle and necrotic and suppurative conditions of the foot in ruminants, pigs and horses (Table 15.1). being isolated from ruminant foot conditions and other necrotic or suppurative lesions. The major pathogens of veterinary significance described in this chapter are Fusobacterium necrophorum and Dichelobacter nodosus, with organisms such as Prevotella spp. Some of the more common infections are shown in Table 15.1. The conditions caused by these non-sporing anaerobes include soft tissue abscessation and cellulitis, post-operative wound infections, periodontal abscesses, aspiration pneumonia, lung and liver abscesses, peritonitis, pleuritis, myometritis, osteomyelitis, mastitis and footrot. This can occur through trauma and necrosis, ischaemia, parasitic invasion or concomitant multiplication of facultative anaerobes. Six genera of Gram-negative rods (Bacteroides, Prevotella, Porphyromonas, Fusobacterium, Bilophila and Sutterella spp.) 2. For these strict anaerobes to multiply at a focus in animal tissue the redox potential of the tissues must be lowered. The infections are often endogenous from normal flora at the site or may be wounds contaminated by nearby flora.
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