I used to work in the phage field and apart from regulation (phages are near impossible to get approved by the FDA), the big problem is the phages people have isolated have a very narrow specificity - most target only individual strains of a specific bacterial species (i.e. they have a very narrow host range). This means you need to have hundred or thousands of different phages to treat even a single bacterial species.
The really interesting thing is that there are phages that have a broad host range (multi-species or even multi-genera), but due to the nature of how phages are typically isolated they are not often found by researchers. Phages, like other living organisms, show differences in ecological adaption with some being specialists (leopards) while others are generalists (rats). The specialists grow faster in their specific hosts than the generalists do so in the normal isolation process which uses a single host bacteria strain (plaque plate assay) and so they appear first. The generalists grow slightly slower and so are typically missed by the scientists.
In my lab we developed a different assay that favoured the isolation of generalist phages and we were really successful in finding broad host range phages (many were multi-genera in host range). I no longer work in this area and it is something I miss as it is such an interesting topic :(
In my lab we developed a different assay that favoured the isolation of generalist phages and we were really successful in finding broad host range phages (many were multi-genera in host range).
Did your group publish anything on this approach? If so, could you share a link to one or some of the papers?
Yes we did, but we didn’t make a huge deal about it in the papers (it is just in the methods sections). If you want to find my phage papers just have a look at my profile on ResearchGate [1].
The basic idea is pretty straightforward. Rather than plating a filtered sample directly onto a overlay plate of a single bacterial strain, we pre-enriched for phages in a mixed culture of multiple bacterial strains (we would sometime use up to 50 different strains/species in the one enrichment flask). What this does is give the broad host range phages a competitive advantage since they can reproduce in multiple hosts and outgrow the narrow host range phages. When you plate out onto a specific strain for isolation of the phages you end up with mostly broad host range phages.
The idea is so obvious I am surprised it is not more widely used in the field. It seems to be the norm to just use a single bacterial strain for the phage isolation. I think most people just assume all phages are narrow host range.
The really interesting thing is that there are phages that have a broad host range (multi-species or even multi-genera), but due to the nature of how phages are typically isolated they are not often found by researchers. Phages, like other living organisms, show differences in ecological adaption with some being specialists (leopards) while others are generalists (rats). The specialists grow faster in their specific hosts than the generalists do so in the normal isolation process which uses a single host bacteria strain (plaque plate assay) and so they appear first. The generalists grow slightly slower and so are typically missed by the scientists.
In my lab we developed a different assay that favoured the isolation of generalist phages and we were really successful in finding broad host range phages (many were multi-genera in host range). I no longer work in this area and it is something I miss as it is such an interesting topic :(