Virulence Factors

[lisapoor]

Could anyone help me please..

 

I understand that virulence factors are a microbe's structures or capabilities that allow it to establish itself in a host and cause damage. However what are some examples of virulene factors in gram positive bacteria, gram negative bacteria, viruses and parasites.

 

Can anyone help me with this please.

Thanks in advance for your help...lp

[sabbath]

Most vf of bacteria are proteins I think. I forgot the specific names though. I didn't pay much attention to our microbio classes this year.

 

Try checking this link out: http://en.wikipedia.org/wiki/Virulence

 

ttfn!

[sabbath]

If you want an example of a gram positive bacterium's vf

check this link out: http://en.wikipedia.org/wiki/Streptococcus_pyogenes

 

Toxins are virulence factors. I think the virulence factor varies relative to the specific strain, though there may be similarities in the virulence of gram positive bacterium, as there must be in gram negative.

 

Some strains I remember with noteworthy virulence factors were Streptococcus pyogenes and Pseudomonas aeruginosa...ah I forgot the rest!

[CharonY]

Well, virulence factors are, as you pointed out correctly, factors that contribute to or modulate the pathogenicity of organisms.

However, purely from this definition you can easily deduce that there is no simple way to distinguish between virulence factors and factors essential for apathogenic growth.

For example, the presence of iron transporter produced by bacrtera is essential for the acquisition of iron during host body invasion. If they are absent the bacteria won't proliferate and chances are that they are apathogenic. However, even if they live outside their hosts they need to acquire iron for survival and it might be the very same system (e.g. siderophore mediated iron transport to name an example). Therefore in a pathogenic organism a given system can be defined as a virulence factor, but the same system can also exist in apathogenic organism (and hence cannot be attributed as virulence factor anymore). The characterization as virulence factor is therefore context dependent.

 

In general virulence factors are (as already pointed out) proteins produced by the bacteria which contribute for instance to: attachment (e.g. fimbria), invasion (e.g. invasins), colonization and proliferation (e.g. subtrate uptake), host defence avoidance (e.g. hydrolases, cell envelope modifications) and finally toxins. However, toxins are often characterized as pathogenicity factors rather than virulence as they can be often directly responsible for the disease rather than contributing to its strength.

[mattbimbo]

i think you are going to end up with a long list of virulence factots. i thought i'd let you know that yeasts and mycobacteria also produce virulence factors.

 

i thought charonY's comments were very good. one could argue over definitions regarding virulence factors, especially in the context of viruses. for instance strains of influenza can be fatal to their hosts, now are these strains more virulent than other influenza strains which does not cause death to their host? surely by killing their host, the first strain is in fact reducing its chances of survival.

[CharonY]

Per definitionem every pathogenic organism posesses virulence factors. As such a long list does not make much sense (except in the context of each specific organism). Actually virulence is usually measured within a given host-pathogen interaction. Therefore strains that kill most efficiently are regarded as the most virulent ones. The resulting fitness reduction of the pathogen is usually not taken into account. For a given system there is of course some kind of optimal virulence which has the optimal fitness for the pathogen, but this is something different.

[ecoli]

yeah, there more of a very general group of proteins that are classed together more out of function then form. IN Uropathogenic E. coli, virulence factors are pili - hair-like proteins, that are secreted from the outer membrance. They bind on the cell receptors in your urinary tract, so they don't get washed away by urine. Then, they infect.