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"In silico"


From Wikipedia
If the target host* of a phage therapy treatment is not an animal the term "biocontrol" (as in phage-mediated biocontrol of bacteria) is usually employed, rather than "phage therapy".

In silico
From:"Genomics,Proteomics and Clinical Bacteriology",N.Woodford and Alan P.Johnson

Phrase that emphasizes the fact that many molecular biologists spend increasing amounts of their time in front of a computer screen, generating hypotheses that can subsequently be tested and (hopefully) confirmed in the laboratory.


Phage Therapy is influenced by:

Phage therapy is influenced by:

Country : the epidemiological situation is different from country to country in terms of circulating bacteria and bacteriophages. Example: lytic phages from Italy may be no active on the same bacteria (genus and species) isolated from another country and vice versa.
Temporariness
Mutation rate
Phenotypical delay
Phage cocktail

My point of view

Wednesday 2 September 2009

Phenotypical Delay in detail


A lot of
scientific works regarding Phage Therapy when describe the disadvantages of this application immediately list the appearance of bacterial resistance to used phages. The authors do not explain the cause and they consider the bacterial resistance as an immediate process but this is not true.

The probability of appearance of bacterial resistance to phages is real but it is important to know how it reveals itself.

When there is a bacterial mutation before the appearance of the corresponding phenotypical effect in the bacterial cell it is necessary a bacterial growth for a long time ( this is the phenotypical delay phenomenon).

For one phage there are about 200 specific receptors on the bacterial cell wall.

If one bacterial cell has a mutation regarding one specific type of phage receptor this bacterial cell requires a long time both for the mutation appearance in its receptors and for a complete dilution of the old phage receptors.

In this moment this bacterial cell is still sensible to phage.


This bacterial cell is sensible to phage up to a complete replacement of all receptors ( 200 ) with the new receptors. This will happen after 12 bacterial cell divisions ( R.Y.Stainier, M.L.Wheelis, J.L.Ingraham and P.R.Painter: “The Microbial World”, 1975) and for this reason we have the time for phage cocktail action.