Bacteria virulence

Studies on S-layers present on the cell envelopes of a great variety of pathogenic organisms [100] revealed that these crystalhne arrays can represent important virulence factors. Most detailed studies have been performed on the fish pathogenic bacteria Aeromonas salmonicida and Aeromonas hydrophila [102] and the human pathogen Campylobacter fetus uh p. fetus [103] and Bacillus anthracis [104]. For example, whole-cell preparations or partially purified cell products are currently used as attenuated vaccines against various fish pathogens [102,105]. 

BCG Cultures of live BCG cells in liquid or on solid media 1 Bacteria centrifuged from medium 2 Resuspension in stabilizer 3 Freeze-drying Viable count induction of sensitivity to tuberculin in guinea-pigs Exclusion of virulent mycobacteria absence of excessive dermal reactivity... 

In some cases pectinolytic enzymes have been associated with virulence and it is generally accepted that pectinolysis by these bacteria facilitates their entry and spread in plant tissue. In Rhizohium, these enzymes may play a role in the root infection process that precedes nodule formation (Hubbell et al 1978). A. irakense has never been reported to be pathogenic on plants. It can therefore be speculated that moderate and strictly regulated pectinolysis of A. irakense facilitates entry in the outer cortex of plants roots, since A. irakense has been isolated from surface-sterilized roots. It is likely that breakdown of plant polysaccharides by root colonizing bacteria can provide them with extra carbon source. 

There are several other host factors present that should be mentioned that inhibit what are known as bacterial virulence factors. In general, these virulence factors are mechanisms that bacteria utilize to cause infection and/or ensure their survival. 

Although bacteria have a single essential chromosome, one DNA molecule responsible for their genetic material, they may also contain extrachromosomal DNA. One variety of such DNA is viral DNA. This DNA can become incorporated into the chromosome and reproduced with it (lysogenic bacteria) or can become virulent — produced independently from the chromosome DNA — when it will cause lysis i.e. cell breakdown. The compound cis-[Pt(NH3)2Cl2] causes the change from... 

Low-iron stress in the host is a signal for pathogenic bacteria to induce virulence factors, such as Shiga-like toxin and haemolysins (although haemolysins could also help to obtain iron from lysed cells and could be grouped under iron uptake ). 

Pathogenic bacteria often make use of siderophores to obtain iron from their host organisms, and consequently the ironbinding capacity of the siderophore is closely related to the bacterial virulence. Enterobactin (1) is the natural siderophore... 

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