The characterized supramolecular structures of endo- and exospores become a target for modern biotechnologies on the principle of “learning from Nature”. The relevance of the research and the prospectiveness of the study of spores mediates the need to disclose their biochemical structure, molecular mechanisms of steadiness, as well as detection and indication using modern analytical tools. cereus (toxicoinfection), as well as representatives of the genus Clostridium – C. Spores are an infectious form of spore-forming bacteria, among which the most dangerous are B. As soon as spores get into human or animal organisms, as well as into canned foods, they germinate and become a source of serious infectious diseases. The unique properties of bacterial spores cause increased scientific and medical interest associated with the epidemiological significance of resting cell forms that can be in a metabolically inactive state for tens and hundreds of years. The extraordinary resistance of spores to extreme physical and chemical conditions of existence is the main distinguishing feature from vegetative forms, and their life cycle contributes to the wide spread of spore-forming bacteria in various ecosystems. These resting (dormant) cells, recognized as the most stable form of life on Earth, are formed in the mother cell with a lack of nutrients. Bacterial controversies have been studied for a long time and yet they remain not fully recognized as objects of the microworld. can exist in two alternative states: vegetative and in the form of endospores, which are divided into two types: having an outer shell (exosporium) and not having it. nodosus is given in Table 15.2.Some gram-positive bacteria of the genus Bacillus spp. A summary of major virulence factors of F. nodosus may have importance as a source of alternative fimbrial antigens. Such events would explain some of the difficulties encountered in control of footrot by vaccination and suggest that benign strains of D. 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. Its major virulence factor is a leukotoxin. ![]() 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. ![]() 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.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |