Monitoring the Ecology vs. Evolutionary Biology of Phage Resistance: A Tale of Two Precisions

Stephen T. Abedon

Department of Microbiology – The Ohio State University

phage.org – phage-therapy.org – biologyaspoetry.org


An important question for those with ecological and evolutionary biological interests is when a given situation is of ecological relevance vs. when it might be more of evolutionary biological importance (Abedon, 2022b). Telling the difference can be important for all of us.

Ecology by definition is the interaction of organisms with their environments.

We can describe phage use as antibacterial agents, that is, phage therapy, as an example of community ecology, or more precisely an applied community ecology. This is community ecology because there is more than one species of organism involved, i.e., as making up an ecological community. Minimally this is the phage (species #1) and the targeted bacterium (species #2), but also of importance is the treated body (species #3).

By definition, bacterial resistance to phages is ecological, as it describes a specific type of interaction, in this case between at least two species, the phage and the bacterium. That the resistance ‘interaction’ is one of ‘non-‘ or ‘less-‘ contact by the bacterium with the phage antagonist is only a detail, just so long as this lack of interaction is phenotypic, i.e., as opposed to the phage and bacterium instead just happening to exist in different places.

Bacterial resistance to phages also of course can have evolutionary aspects.

Evolution by definition is a change in allele frequencies in at least one species, or, more precisely, changes in allele frequencies in one population, in either case as observed over time.

Often the changes in allele frequency that we care most about are consequences of the impact of natural selection, and natural selection under most circumstances has a strong ecological component. Indeed, natural selection in most cases can be defined as the impact of ecology on evolutionary biology (and hence, as an aside, the existence of the science of evolutionary ecology).

By definition yet again, changes in the frequency of phage-resistance alleles within a bacterial population is an evolutionary process and typically these changes are a consequence of natural selection. The selective agent would be that phage population that is negatively affecting a bacterial population, resulting in increases in the frequency of whatever bacterial alleles are conferring protection from this phage.

Of interest to phage therapy is that this ecology driving evolutionary biology can in turn drive ecology. Specifically, once the frequency of alleles conferring phage resistance are high enough within a targeted bacterial population, then the applied community ecology of phage therapy can be affected, e.g., phage therapy can stop working.

In addition, if the frequency of a phage-resisting allele is found to be 100% within the bacterial population, following phage treatment (i.e., a frequency of 1.0), then if nothing else this is indicative that bacterial survival – an ecological issue – in this instance likely is a function of the occurrence of phage resistance.

If the frequency of phage resistance instead is 0% following phage treatment (0.0), then if nothing else this is indicative that bacterial survival (again, an ecological issue) was not a function of the occurrence of phage resistance. In fact, any frequency of phage resistance below 100% within a targeted bacterial population means that phage-sensitive bacteria are persisting despite phage treatment. For an example of the latter, see, e.g., Box 2 of Abedon (2022c).

Phage-resistant bacteria may display reduced virulence against bodies or may be subsequently treated with a different phage. Consequently, in some ways phage-resistant bacteria are not necessarily that big of a deal as a midpoint of a phage treatment, and this can be particularly if a diversity of other treatment phages are available. Phage resistance is not desired nor welcome, of course, but evolution of phage resistance also is not a certain indication of phage therapy microbiological failure.

That, by the way, to a degree contrasts with the evolution of antibiotic resistance that can occur over the course of antibiotic treatments, which can indeed be associated with treatment failures with high likelihood. One difference is something called antagonistic pleiotropy – not to be confused with antagonistic coevolution (Abedon, 2022a)!!! – i.e., whether or not resistance alleles are otherwise costly to the carrying organism (Abedon, 2022d). If resistance is both easily attained and not ecologically costly, then, well, that can be problematic, particularly given only mono therapies. Another difference is the sheer abundance of diverse, typically safe-to-use phages that often can be available to phage therapists (Abedon and Thomas-Abedon, 2010).

In any case, the persistence of phage-sensitive bacteria despite phage treatment probably means that, for whatever reason, treatment phages are not able to successful infect targeted bacteria despite those bacteria being phage sensitive; again, see Box 2 of Abedon (2022c). This frankly should be viewed as a big deal as essentially by definition it implies a phage therapy microbiological failure, one that may or may not be easily rectified, or at least a lack of complete eradication of phage-sensitive bacteria. I mean, how does one deal with phages not being able to easily reach and/or kill the otherwise phage-sensitive bacteria they are targeting?

Perhaps, as an answer to that question, some other phage that happens to be able to do a better job of reaching and/or killing those otherwise phage-sensitive bacteria might be available for use. That certainly is possible, but at this point in time we really aren’t all that good at figuring out what might constitute a better phage for phage therapy, other than in terms of host range – though see for example Bull et al. (2002; 2019) – and particularly better than the phage that we started with, presumably assuming that the first phage tried we thought was the better phage for phage therapy, hence why it was used first.

Of course, we almost take it as a matter of faith that phage carriage of extracellular polymeric substance (EPS) depolymerases (Danis-Wlodarczyk et al., 2021b) will solve many problems of phage penetration to targeted bacteria. But whether that is actually true in all instances, e.g., such as phage distribution throughout lungs – yet again, see Box 2 of Abedon (2022c) – is in my opinion just not known.

How might use of a phage cocktail instead result in complete eradication of a phage sensitive bacteria when a monophage does not? Just better odds that at least one of the phages used will be particularly good at achieving this? As another aside (Danis-Wlodarczyk et al., 2021a; Abedon, 2022c), note that it can be helpful to just apply a phage or phages at higher or multiple doses before giving up on a given treatment strategy!

At any rate, not being able to eradicate bacteria from an infection even though those bacteria are sensitive to a given treatment can be a far greater problem than failure that get rid of bacteria that explicitly are not susceptible to a treatment protocol. That is, there exits a basic problem in the applied ecology of treatments if not even phage-sensitive bacteria can be removed in full, just as there is a basic problem for an antibiotic treatment if the antibiotic is unable to fully eliminate even antibiotic-sensitive bacteria, a.k.a., the concept of antibiotic tolerance. For a bit on the latter, see Appendix A1 of in fact yet yet again, Abedon (2022c).

So where exactly am I going with this? At the end of a phage treatment, it is important to know whether the frequency of phage-resistant bacteria among the targeted bacterial population is high (at or approaching 100%) rather than low (near 0%). But high precision in that measurement, e.g., more than just whole percentage-point differences, really is not all that important. Why not?

Especially ecologically, there likely is little difference between 0.1%, 0.01%, or even maybe 10% or 50% of the bacteria being phage resistant, as that will still leave an awful lot of phage-sensitive bacteria having escaped phages during treatment. At some probably higher frequency of phage resistance we might come to feel that the frequency of remaining phage-sensitive bacteria is less important, but exactly where that point lies is difficult to say. My gut feeling, though, is that at the point where we start having to do statistics to tell the difference, i.e., at a point where higher precision in measurements becomes important, the importance of differences in the frequencies of phage-resistant bacteria – 100% or a tiny bit less than 100% – probably are no longer all that relevant. (For consideration of the statistics of plating-based enumeration, see Abedon and Katsaounis, 2021.)

Ah, you are saying, clearly therefore I am leading up to claiming that if we are interested instead in the evolutionary biology phage resistance, then in that case we really should care about measuring resistance frequencies with higher precision. And you would be absolutely right!  Except also maybe not.

The problem here is that a key word in the definition of evolution that we are using is “Change”, and by definition change cannot be measured using only a single data point, or in the case of quantifying evolutionary change, a single time point. Thus, no matter how precisely you measure the endpoint frequency of phage-resistant bacteria, that will not tell you that evolution has occurred in the course of phage therapy treatment, much less how much evolution.

Here is the basis of this latter point: At the start of an experiment, if your population of bacteria ever is going to contain phage-resistant members, then it likely already does contain those mutants (this, by the way, is why only-qualitative determinations that phage resistance is present, e.g., such as following phage treatments, are basically meaningless). Exceptional would be if the starting number of bacteria involved is so low that this number is, e.g., less than the inverse of the rate of mutation to phage resistance. Thus, for every time a bacterium divides, let’s say that there is a probability of 10-5 that a mutation to phage-resistance will occur. If so, then in a population of 106 bacteria, on average 10 phage-resistant bacteria will be expected to be present, more or less (Abedon et al., 2021).

That last part, “More or less”, is crucial, however, as the frequency with which mutations conferring phage resistance are expected to be present is predicted to somewhat “Fluctuate” about an average (Luria and Delbrück, 1943). In practice, this means that even if you precisely know bacterial rates of mutation to resistance to a given phage, you still will not know how many phage-resistant bacterial mutants will be present prior to the start of treatments. (As yet another aside, actually calculating mutation rates, vs. just mutant frequencies, is a not trivial thing to do.)

Without knowing the frequency of phage resistance prior to the start of treatments, then you are only really guessing whether evolution has occurred in the course of a phage treatment, no matter how precisely frequencies of phage resistance may be measured after a treatment is done.

In short, ecologically, the precision of measures of frequencies of bacterial phage resistance need not be all that high to possess high value in understanding the outcome of phage treatments. I mean, either phage-sensitive bacteria have persisted despite prior treatments or they have not, without a need to describe percentages with precision past the decimal point. Thus, 50.0% vs. 50.1%? Who cares? Indeed, 50% vs. 51%, who cares?

Alternatively, if one really cares about being precise in monitoring the evolution of phage resistance, then the most important place to emphasize that precision actually should be prior to the start of treatments, i.e., prior to initial phage application, and only then should one be measuring frequencies of phage resistance after treatments as well. But don’t forget that you need to have this information for explicitly that bacterial culture that is being treated, since evolutionarily all we really will care about is how a specific bacterial culture as a population changes in allele frequencies over time, and in phage therapy that bacterial population is precisely the one that you are treating.

Even so, how much more than order-of-magnitude precision do we really need in monitoring the evolution of phage resistance during phage treatments? Will we really care for example if the frequency of phage-resistant bacteria have changed from 10-5 to 10-5.5? And how hard would we have to try to be sure that such a relatively small change is actually real? I mean, seriously, except for the most hard-core evolutionary experiments, who would really care?

For what it is worth, when I look at the outcome of a phage treatment, if all of the targeted bacteria remaining are phage resistant, then I know what went wrong (clue: the bacteria have evolved resistance to the treatment phages, i.e., an evolutionary outcome). But when I look at the outcome of a phage therapy experiment and a substantial portion of the bacteria remaining are still phage sensitive, then more often than not I can only speculate as to what might have gone wrong, except again for those bacteria that have evolved phage resistance (Abedon, 2022c).  Still, this latter scenario should be viewed at least as an ecologically relevant outcome.

But bottom line: Obtaining an additional decimal place or two in describing the frequency of phage-resisting alleles within the treated bacterial population generally will not greatly aid in improving the precision of our applied ecological speculation.

Afterthought:

You would think that this essay came into existence as a natural outgrowth of the cited publications, particularly Abedon (2022c), but you would be wrong! On the other hand, I did wait a few months until that publication was published and available open access. Thanks for your interest!

Literature Cited:

Abedon, S. T. 2022a. A primer on phage-bacterium antagonistic coevolution, p. 293-315. In Bacteriophages as Drivers of Evolution: An Evolutionary Ecological Perspective. Springer, Cham, Switzerland. https://link.springer.com/chapter/10.1007/978-3-030-94309-7_25

Abedon, S. T. 2022b. Frequency-dependent selection in light of phage exposure, p. 275-292. In  Bacteriophages as Drivers of Evolution: An Evolutionary Ecological Perspective. Springer, Cham, Switzerland. https://link.springer.com/chapter/10.1007/978-3-030-94309-7_24

Abedon, S. T. 2022c. Further considerations on how to improve phage therapy experimentation, practice, and reporting: pharmacodynamics perspectives. Phage 3:95-97. https://www.liebertpub.com/doi/full/10.1089/phage.2022.0019

Abedon, S. T. 2022d. Pleiotropic costs of phage resistance, p. 253-262. In Bacteriophages as Drivers of Evolution: An Evolutionary Ecological Perspective. Springer, Cham, Switzerland. https://link.springer.com/chapter/10.1007/978-3-030-94309-7_22

Abedon, S. T., and C. Thomas-Abedon. 2010. Phage therapy pharmacology. Curr. Pharm. Biotechnol. 11:28-47. https://pubmed.ncbi.nlm.nih.gov/20214606/

Abedon, S. T., and T. I. Katsaounis. 2021. Detection of bacteriophages: statistical aspects of plaque assay, p. 539-560. In D. Harper, S. T. Abedon, B. H. Burrowes, and M. McConville (ed.), Bacteriophages: Biology, Technology, Therapy. Springer Nature Switzerland AG, New York City. https://link.springer.com/referenceworkentry/10.1007/978-3-319-40598-8_17-1

Abedon, S. T., K. M. Danis-Wlodarczyk, and D. J. Wozniak. 2021. Phage cocktail development for bacteriophage therapy: toward improving spectrum of activity breadth and depth. Pharmaceuticals 14:1019. https://pubmed.ncbi.nlm.nih.gov/34681243/

Bull, J. J., B. R. Levin, T. DeRouin, N. Walker, and C. A. Bloch. 2002. Dynamics of success and failure in phage and antibiotic therapy in experimental infections. BMC Microbiol. 2:35. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC138797/

Bull, J. J., B. R. Levin, and I. J. Molineux. 2019. Promises and pitfalls of in vivo evolution to improve phage therapy. Viruses 11:1083. https://pubmed.ncbi.nlm.nih.gov/31766537/

Danis-Wlodarczyk, K., K. Dabrowska, and S. T. Abedon. 2021a. Phage therapy: the pharmacology of antibacterial viruses. Curr. Issues Mol. Biol. 40:81-164. https://pubmed.ncbi.nlm.nih.gov/32503951/

Danis-Wlodarczyk, K. M., D. J. Wozniak, and S. T. Abedon. 2021b. Treating bacterial infections with bacteriophage-based enzybiotics: in vitro, in vivo and clinical application. Antibiotics 10:1497. https://pubmed.ncbi.nlm.nih.gov/34943709/

Luria, S. E., and M. Delbrück. 1943. Mutations of bacteria from virus sensitivity to virus resistance. Genetics 28:491-511. https://pubmed.ncbi.nlm.nih.gov/17247100/

Virion Location of Most Phage Depolymerases

Stephen T. Abedon

Department of Microbiology – The Ohio State University

phage.org – phage-therapy.org – biologyaspoetry.org


 

Here is a something worth knowing about, from Pires, D.P., H. Oliveira, L.D. Melo, S. Sillankorva, and J. Azeredo. 2016. Bacteriophage-encoded depolymerases: their diversity and biotechnological applications.  Appl. Microbiol. Biotechnol. 100:2141-2151. [PubMed], (calls to figure and table excluded from quote):

Based on our search, the huge majority of phage depolymerases (126 proteins) are encoded in the same open reading frame of phage structural proteins (mostly on tail fibers, base plates, but sometimes also in the neck) or in close proximity to those genes, and were thus considered as structural proteins. Twenty other depolymerases found in this work might be soluble proteins since they are distant from any structural gene.

Depolymerases that are only soluble, that is, not virion attached, presumably are only useful in the immediate vicinity of phage-lysed bacteria, e.g., towards phage burrowing more deeply into biofilms. This perhaps means that phages don’t need depolymerases to initially infect biofilm bacteria (see here for that argument). Depolymerases that are associated with virions, by contrast, presumably are useful as well upon initial phage encounter with a biofilm bacterium.

That the majority of depolymerases are may not be soluble, but instead appear to be associated with virions, is suggestive that depolymerases are employed for the sake of initial encounter between virions and biofilm bacteteria. But this then begs the question of why more phages don’t encoded depolymerases?

Is it that we have trouble recognizing them in sequence data? Is it that bacteria are just too diverse in terms of extracellular polymers produced? (In addition to limiting utility, the latter may also interfere with our ability to detect depolymerase phenotypes during phage growth as plaques.) Is it because for the most part phages can infect biofilm bacteria sufficiently even without depolymerases? Or are there unexplored trade-offs associated with depolymerase encoding, perhaps especially when they are present as structural components of phage virions?

In the three previous paragraphs I am drawing on a tiny bit of past thought as to the role of depolymerases in phage interaction with biofilms, as can be found in my 2011 book, Bacteriophages and Biofilms. In particular, from p. 23 (of the revised pagination version, or p. 27 of the original… don’t ask…):

Ecologically, EPS depolymerases improve phage movement that occurs either adjacent to or distant from a phage’s parental infection. If distant, then movement towards bacteria will be enhanced by physical linkage between virions and depolymerases. Alternatively, for more localized movement, then soluble depolymerases may suffice, such as for phage dissemination out of biofilms [2004]. Scholl et al. [2005] thus found that efficiency of plating (EOP) was low for phages encoding a soluble EPS depolymerase when infecting a K1 capsule-producing strain and that an isogenic phage not encoding the depolymerase is “unable to form plaques on lawns of this strain” (p. 4872). This result is suggestive that though initiation of plaques occurred with low efficiency, once those infections commenced then subsequent EPS depolymerization presumably facilitated phage migration towards adjacent bacteria to complete plaque formation. In circumstances where enzymes may not be directly supplied, it should thus be advantageous for those enzymes to be carried by virion particles, if only to increase the efficiency of initial infection. That is, it should be advantageous to phages for enzymes to be present at the point of phage adsorption, by being virion attached, rather than present only immediately following the lyses of phage-infected bacteria [I then illustrate this argument with a figure…].

 

 

 

Attacking Biofilms: Another Quote, Plus Some Discussion

Stephen T. Abedon

Department of Microbiology – The Ohio State University

phage.org – phage-therapy.org – biologyaspoetry.org


 

This quote is from Lee Watkins and J. W. Costerton (1984). Growth and biocide resistance of bacterial biofilms in industrial systems. Chemical Times and Trends (October):35-40.

The article has nothing to do with viruses. The quote is interesting, however, since it speaks to the question of how exactly to employ viruses in the biocontrol of microorganisms, specifically in the biocontrol and indeed elimination of biofilms from surfaces (quotation marks in the original):

lt is important to be able to answer that old question “Shall we slug with a biocide, shall we continuously treat with a biocide or shall we soak with a biocide—what is the best deal for the situation?”

To me these three alternatives are distinguishable in terms of how we might think about treatment of bacteria or biofilms with phages, that is, phage-mediated biocontrol of bacteria, or phage therapy.

The first alternative I interpret as the application of large amounts of biocide over short periods, perhaps in a single dose, i.e., slugging, or what we might describe as passive treatment in the case of phage therapy. Keep in mind that passive treatment should mean that for every bacterium targeted not only should at least 10 phages be added but at least 10 phages should be adsorbing, per adsorbable bacterium.

Continuous application, to me, would imply the application of lower but still minimally effective concentrations of biocide over longer periods. Continuous application represents an extreme of multiple dosing, i.e., where the time gap between applications is reduced to zero. Key here is that something other than overwhelming amounts of biocide is being applied, what many (unfortunately) would describe as something other than high multiplicities of infection (MOI) in the case of phage application. One can view such continuous application a preventive, or prophylactic.

Lastly there is soaking, which could also be viewed as continuous application, though this is an application that takes place over a relatively short period, i.e., days or weeks rather than months or years. This would be equivalent to the application of phages by soaking bandages, soaking various absorbent material (one sees mention of “tampons” in various places in the phage therapy literature, though it’s important to realize that the word has a medical definition), or instead via the application of, e.g., Phage Bioderm (for example, as discussed here).

What’s missing, of course, are any assumptions that the biocide will replicate in situ, i.e., so-called active treatment, which is typically considered to be a hallmark of phage-mediated biocontrol/phage therapy. That absence, though, is not unexpected given that this is from a discussion of chemical and physical anti-biofilm biocides rather than of phages.

Still, it once again is nice to see that there really is little that is new under the sun. When dealing with bacterial infections, particularly chronic ones which are associated with biofilms, it can be important to keep in mind these ideas:

  1. We can hit them very hard (literally overkill) over short periods,
  2. We can hit them less hard (minimally adequate biocide concentrations) but over long periods, perhaps particularly towards prevention, or
  3. We can soak the infections over intermediate periods, presumably with periodic re-invigoration of dosing, using antibacterial levels which, also presumably, are somewhat in excess of what might be viewed as minimally adequate.

Any other approach, unless backed by hard data, should be considered to represent mostly wishful thinking.

Some additional reading:

Abedon, S.T. 2016. Bacteriophage exploitation of bacterial biofilms: phage preference for less mature targets?  FEMS Microbiol. Lett. 363:fnv246. [PubMed]

Abedon, S.T. 2016. Commentary: phage therapy of staphylococcal chronic osteomyelitis in experimental animal model.  Front. Microbiol. 7:1251. [PubMed]

Abedon, S.T. 2016. Phage therapy dosing: The problem(s) with multiplicity of infection (MOI).  Bacteriophage 6:e1220348. [PubMed]

Abedon, S.T. 2014. Bacteriophages as drugs: the pharmacology of phage therapy., p. 69-100. In J. Borysowski, R. Miedzybrodzki, and A. Górski (eds.), Phage Therapy: Current Research and Applications. Caister Academic Press, Norfolk, UK.

Abedon, S. 2011. Phage therapy pharmacology: calculating phage dosing.  Adv. Appl. Microbiol. 77:1-40. [PubMed]

Abedon, S.T., S.J. Kuhl, B.G. Blasdel, and E.M. Kutter. 2011. Phage treatment of human infections.  Bacteriophage 1:66-85. [PubMed]

Abedon, S.T. and C. Thomas-Abedon. 2010. Phage therapy pharmacology.  Curr. Pharm. Biotechnol. 11:28-47. [PubMed]

Bacterial Lawns as Biofilm-Like Environments: A New Old Quotation

Stephen T. Abedon

Department of Microbiology – The Ohio State University

phage.org – phage-therapy.org – biologyaspoetry.org


 

Way back in 2010 we (Abedon and Thomas-Abedon) suggested that the growth of phage plaques within bacterial lawns could serve as mimics of bacteriophage interaction with bacterial biofiolms. In fact, we made a rather extensive argument with six Roman numeraled points: (i) constraint of bacterial movement, (ii) bacterial growth within lawns as microcolonies, (iii) inhibition of phage movement, (iv) plaque-like phage growth within actual biofilms, (v) possible temporary shielding of bacteria within lawn microcolonies from phage attack, and (vi) variation in bacterial physiologies again as found within microcolonies within lawns and as potentially equivalent to bacterial microcolonies within biofilms. We concluded that, “Given these similarities, phage plaques as a facile laboratory model therefore could enrich our understanding of phage-bacterial interrelations as they may occur during the phage therapy of biofilm-producing bacterial infections.”

Indeed, we noted as well that Gallet et al. (2009) described phage formation of plaques also as phage growth within a “biofilm-like environment”.

Here I provide a quote from an earlier publication which serves to further these arguments. From Gilbert and Brown (1995) [Mechanisms of the protection of bacterial biofilms from antibacterial agents, p. 118-130. In J. W. Costerton and H. Lappin-Scott (ed.), Microbial biofilms. Cambridge University Press, Cambridge, UK.], p. 119:

The most simple in vitro method of generating biofilms to study antimicrobial sensitivity is to inoculate the surface of an agar plate to produce a confluent growth. Such cultures, whilst not fully duplicating the in vivo situation, have been suggested to model the close proximity of individual cells to one another and the various gradients found in biofilms. In this respect, colonies grown on agar may bе representative of biofilms at solid-air interfaces.

Of course, one cannot claim that bacteria growing within soft agar overlays are perfect representations of naturally occurring biofilm structures. Nonetheless, as we’ve noted previously, e.g., Abedon and Yin (2009), plaque formation within them is a lot more complex than people otherwise may realize.

Phage Tails as Polymeric Substance Probes: Arguments For and Against

Stephen T. Abedon

Department of Microbiology – The Ohio State University

phage.org – phage-therapy.org – biologyaspoetry.org


 

Recently I suggested that:

Phage tails, to the extent that they display smaller diameters than phage virions as a whole, might contribute to nonenzymatic virion translocation into EPS [Extracellular Polymeric Substance, i.e. as associated with biofilm matrix], perhaps with longer, narrower tails permitting deeper or faster local penetration to biofilm-surface located bacteria.

Perhaps not unexpectedly, I now find that this was not an entirely original thought. From Wilkinson (1958), p. 68:

Physical blocking of the surface receptor. Can the presence of a capsule protect the cell simply because of its physical properties? Presumably an infective phage must be able to inject its DNA through the cytoplasmic membrane and, therefore, the main body of the phage must be at a distance from the cytoplasmic membrane smaller than the length of the phage tail (rarely longer than 150 mµ [meaning 150 nm]). Therefore, any layer outside the cytoplasmic membrane which is greater in thickness than 150 mµ and is impermeable to phages will act as a nonspecific phage inhibitor. It has already been shown that a capsule is by definition greater than 150 mµ in thickness and that
it is probably impermeable to particles of the size of a phage head (about 100 mµ). An additional barrier to the phage might be the high negative charge of the polysaccharide capsular surface. In confirmation of this role, capsulate bacteria have been reported to be generally phage resistant…

In my defense, my suggestion pointed specifically to longer phage tails, and the general thrust of my article was that it is especially less mature aspects of biofilms which may be more vulnerable to phages. Less maturity, in other words, might be associated with less thick biofilm matrix, e.g., as perhaps associated with new growth on biofilm surfaces.

Indeed, Wilkinson discusses further an article, unfortunately which is not in English, suggesting that when polymeric substance material is thinner then successful phage adsorption may be more likely (as continuing directly from the previous quote):

Thus, Kauffmann and Vahlne (82) found that most capsulate strains of E. coli were resistant to phage and that when capsulate strains were attacked, there was a proportionality between the thickness of the capsule and the resistance.

One could speculate therefore that it could be, conversely, that shorter tails would be less able to penetrate thicker “capsulate”.

It should be noted that I am making no claims that phage tails exist solely for the sake of penetrating extracellular polymers towards adsorption of bacteria, though it is entirely possible that such penetration could serve as a benefit of possessing especially “longer, narrower tails”.

Freezing Selects for Phage T7 Deletion Mutations… Not!

Stephen T. Abedon

Department of Microbiology – The Ohio State University

phage.org – phage-therapy.org – biologyaspoetry.org


 

Myth: Freezing phage T7 can select for deletion mutations…

From Clark and Geary (1973), with emphasis added:

ATCC freeze-dries phages for distribution (Clark and Geary, 1969). Davis and Hyman (1971) have reported the existence of at least two authentically different T7 phage strains, T7M (Meselsohn) and T7L (Luria) (ATCC 11303-B7). They also stated that T7L lyophilized stock from ATCC contained a high percentage of deletions in the DNA molecule, and they attributed this to lyophilization selecting for DNA deletions. However, since this publication, ATCC prevailed upon these authors to test the ATCC broth stock of T7L, which had been maintained at 4° C unlyophilized or unfrozen since its deposit in the Collection by Luria in 1952. They reported in a letter to W. A. Clark that the T7L stock before freeze-drying contained the same deletions as the freeze-dried product.

In other words, the evidence is not consistent with freezing selecting for deletion mutations in phage T7…

REFERENCES

Clark, W. A., and D. Geary. 1969. The collection of bacteriophages at the American Type Culture Collection, p. 179-187. In T. Nei (ed.), Freezing and Drying Microorganisms. University Park Press, Baltimore.

Clark, W. A., and D. Geary. 1973. Preservation of bacteriophages by freezing and freeze-drying. Cryobiology 10:351-360.

Davis, R. W., and R. W. Hyman. 1971. A study of evolution: The DNA base sequence homology between coliphages T3 and T7. J. Mol. Biol. 62:287-301.

d’Hérelle, F. (1918). Sur le rôle du microbe filtrant bactériophage dans la dysentérie bacillaire. Compt. rend. Acad. Sci. 167:970-972.

Stephen T. Abedon

Department of Microbiology – The Ohio State University

phage.org – phage-therapy.org – biologyaspoetry.org


 

I’ve been meaning to post machine-translated articles for some time now. Here is what you are seeing:

  • The posts are broken up by paragraphs with three sections per
  • The first section is the paragraph more or less retaining original page breaks (for easier reconciliation with the original document)
  • The second section is the paragraphs minus those page breaks
  • The third section, in bold, is the translation generated by Google with occasional help from a human being (e.g., moi)

Please feel free to make suggestions as to how to improve transcriptions and/or translations.

Oh, yes, and feel free to skip to the last “sentence” (actually, fragment), which, I think, is historically the most important point of the article.

BACTÉRIOLOGIE. – Sur le rôle du microbe filtrant bactériophage dans la

dysenterie bacillaire. Note de M. F. D’HÉRELLE, présentée par M. Roux.

 

BACTÉRIOLOGIE. – Sur le rôle du microbe filtrant bactériophage dans la dysenterie bacillaire. Note de M. F. D’HÉRELLE, présentée par M. Roux.

BACTERIOLOGY. – On the role of the filter microbe bacteriophage in bacillary dysentery. Note to Mr. F. D’HÉRELLE, by Mr Roux.

 

Dans une Note préliminaire (1) j’ai décrit un microbe filtrant trouvé

dans les déjections des convalèscents de dysenterie bacillaire. L’emploi

d’une technique moins imparfaite que celle dont je m’étais servi tout

d’abord (2) joint à l’examen systématique des selles de trente-quatre

malades, tous atteints de dysenterie à bacilles de Shiga, et dont plusieurs

ont pu être suivis journellement depuis le début de la maladie jusqu’à la fin

de la convalescence, m’ont permis d’etudier d’une manière plus complète

le mode d’action du microbe bactériophage et de préciser son rôle dans

l’évolution de la maladie.

 

Dans une Note préliminaire (1) j’ai décrit un microbe filtrant trouvé dans les déjections des convalèscents de dysenterie bacillaire. L’emploi d’une technique moins imparfaite que celle dont je m’étais servi tout d’abord (2) joint à l’examen systématique des selles de trente-quatre malades, tous atteints de dysenterie à bacilles de Shiga, et dont plusieurs ont pu être suivis journellement depuis le début de la maladie jusqu’à la fin de la convalescence, m’ont permis d’etudier d’une manière plus complète le mode d’action du microbe bactériophage et de préciser son rôle dans l’évolution de la maladie.

In a preliminary Note (1) I wrote [of] a filter[able] microbe found in excreta of dysentery bacillary [from] convalescents. The use of a technique less imperfect than the one I had used first (2) attached to the systematic examination of stools of thirty-four patients, all dysentery bacilli Shiga, and several of were followed daily from the beginning of the disease until the end of convalescence, allowed me to study in a more complete way the mode of action of the microbe bacteriophage and clarify its role in evolution of the disease.

 

(1) Comptes rendus, t. 165, 1917, p. 373.

(2) Comptes rendus de la Société de Biologie, séance du 7 décembre rg18.

 

Dans les cas de dysenterie bacillaire, même très graves, mais dans lesquels

l’état du patient s’améliore ‘rapidement, le microbe ,bactériophage

manifeste sa présence d’une· manière très active d’emblée, tant sur les cultures

du bacille isolé des déjections du patient que sur les souches du Shiga

du laboratoire, à partir du moment où les symptômes commencent à

s’amender. Le pouvoir bactériophage vis-à-vis du bacille dysentérique cesse

brusquement d’être décelable au début de la convalescence. A· partir de ce

moment, des examens répétés montrent également l’absence de bacilles

pathogènes.

 

Dans les cas de dysenterie bacillaire, même très graves, mais dans lesquels l’état du patient s’améliore ‘rapidement, le microbe ,bactériophage manifeste sa présence d’une manière très active d’emblée, tant sur les cultures du bacille isolé des déjections du patient que sur les souches du Shiga du laboratoire, à partir du moment où les symptômes commencent à s’amender. Le pouvoir bactériophage vis-à-vis du bacille dysentérique cesse brusquement d’être décelable au début de la convalescence. A partir de ce moment, des examens répétés montrent également l’absence de bacilles pathogènes.

In cases of bacillary dysentery, even very serious but in which the patient’s condition is improving quickly, the microbe, bacteriophage demonstrates its presence in a very active from the outset, both cultures of isolated bacillus excreta of the patient as the Shiga strains of laboratory, from the time symptoms begin to mend. Bacteriophage power vis-à-vis the dysentery bacillus suddenly ceases to be detectable in early convalescence. From that moment, repeated examinations also show the absence of pathogenic bacilli.

 

Dans les cas où la maladie se prolonge, le microbe bactériophage ne

manifeste qu’une action mille ou peu marquee, tant que l’état du patient

reste stationnaire. Si, dans quelques cas, l’action bactéricide est reiativement élevée sur les souches ayant subi de nombreux passages sur les

milieux de culture, par contre, elle est toujours inappréciable ou très faible

sur les cultures du bacille provenant du malade en observation. L’amélioration

se manifeste dès que l’action bactériophage devient énergique vis-à-vis de ce dernier.

 

Dans les cas où la maladie se prolonge, le microbe bactériophage ne manifeste qu’une action mille ou peu marquee, tant que l’état du patient reste stationnaire. Si, dans quelques cas, l’action bactéricide est relativement élevée sur les souches ayant subi de nombreux passages sur les milieux de culture, par contre, elle est toujours inappréciable ou très faible sur les cultures du bacille provenant du malade en observation. L’amélioration se manifeste dès que l’action bactériophage devient énergique vis-à-vis de ce dernier.

In cases where the disease is prolonged, the microbe bacteriophage manifesto that an action or a thousand little marquee as long as the patient remains stationary. If, in some cases, the bactericidal action is relatively high stem having undergone many passages on culture media, by cons, it is always invaluable and very low on the cultures of the bacillus from the observation sick. The improvement was evident as soon as the bacteriophage action becomes strong vis-à-vis the latter.

 

Dans les formes de longue durée et à rechutes, le pouvoir bactériophage

du microbe filtrant peut, à certains moments, être très énergique vis-à-vis

des bacilles de culture et variable d’un jour à l’autre, quoique toujours

relativement faible, vis-à-vis du bacille du malade. La guérison suit de près

le moment où l’action du microbe bactériophage se manifeste d’une manière

aussi intense pour l’une comme pour l’autre souche. Cette action persiste;

avec des fluctuations dans l’activité, aussi longtemps que le patient reste

porteur de germes. Ce dernier fait serait même de nature à faciliter le dépistage

des porteurs de germes, la mise en évidence du microbe bactériophage

étant plus simple et plus sûre que la recherche du bacille pathogène dans

les selles.

 

Dans les formes de longue durée et à rechutes, le pouvoir bactériophage du microbe filtrant peut, à certains moments, être très énergique vis-à-vis des bacilles de culture et variable d’un jour à l’autre, quoique toujours relativement faible, vis-à-vis du bacille du malade. La guérison suit de près le moment où l’action du microbe bactériophage se manifeste d’une manière aussi intense pour l’une comme pour l’autre souche. Cette action persiste; avec des fluctuations dans l’activité, aussi longtemps que le patient reste porteur de germes. Ce dernier fait serait même de nature à faciliter le dépistage des porteurs de germes, la mise en évidence du microbe bactériophage étant plus simple et plus sûre que la recherche du bacille pathogène dans les selles.

In the forms of long-term and relapsing, the bacteriophage of the filter microbe authority may, at times, be very aggressive vis-à-vis the bacilli culture and varies from one day to another, though still relatively low, vis-à-vis the bacillus of the patient. Healing closely when the action of the microbe bacteriophage manifests an intense way for the one as for the other strain. This action persists; with fluctuations in activity, as long as the patient remains buoyant germs. The latter would be able to facilitate the screening of carriers, the detection of the bacteriophage microbe is simpler and safer than the search for the pathogenic bacterium in the stool.

 

J’ai pu vérifier que , l’action du microbe bactériophage était prépondérante,

non pas seulement en ce qui touche à la disparition du bacille dysentérique

de l’intestin une fois la maladie déclarée, mais encore lors de son

éclosion. Au cours de la récente épidémie, j’ai eu l’occasion d’observer

plusieurs cas extrêmement bénins dans lesquels les symptômes se limitèrent

à quelques épreintes et à deux ou trois selles diarrhéiques: or, dans

tous ces cas, le microbe bactériophage fut, dès le début, présent et doué

d’un pouvoir antagoniste élevé. Malgré la bénignité de l’affection, il s’agissait

bien de dysenterie car, dans trois de ces cas, je pus isoler de la

première selle diarrhéique émise un bacille de Shiga typique.

 

J’ai pu vérifier que , l’action du microbe bactériophage était prépondérante, non pas seulement en ce qui touche à la disparition du bacille dysentérique de l’intestin une fois la maladie déclarée, mais encore lors de son éclosion. Au cours de la récente épidémie, j’ai eu l’occasion d’observer plusieurs cas extrêmement bénins dans lesquels les symptômes se limitèrent à quelques épreintes et à deux ou trois selles diarrhéiques: or, dans tous ces cas, le microbe bactériophage fut, dès le début, présent et doué d’un pouvoir antagoniste élevé. Malgré la bénignité de l’affection, il s’agissait bien de dysenterie car, dans trois de ces cas, je pus isoler de la première selle diarrhéique émise un bacille de Shiga typique.

I could verify that the action of the bacteriophage was dominant microbe, not only as it relates to the disappearance of dysentery bacillus bowel disease once declared, but during its outbreak. In the recent outbreak, I had the opportunity to observe several extremely mild cases in which symptoms were limited to a few tenesmus and two or three loose stools: gold, in all these cases, the microbe was bacteriophage, from the beginning, and now endowed with a high antagonistic power. Despite the mildness of the disease, it was good of dysentery because in three of these cases, I could isolate the first loose stool issued a typical Shiga bacillus.

 

Le microbe bactériophage préexiste dans l’intestin ou il vit narmalement

aux dépens du B. coli. Dans les selles normales, son pouvoir antagoniste

vis-à-vis de ce dernier bacille est toujours très faible; il peut devenir

considérable dans divers états morbides, dans certaines formes d’entérites

et de diarrhée banales, par exemple. La présence de bacilles dysentériques

dans l’intestin détermine en premier lieu une exaltation considérable de

la virulence du microbe bactériophage vis-à-vis du B. coli, puis, par une

accoutumance plus ou moins rapide, cette virulence s’exalte vis-à-vis du

bacille dysentérique; elle atteint d’emblée ou graduellement une puissance

considérable amenant la disparition rapide ou graduelle du bacille pathogène. Si la virulence du microbe bactériophage s’exalte d’emblée, les

bacilles dysentériques sont détruits dès le début de leur culture dans le

contenu intestinal, la maladie avorte avant tout symptôme ou se borne à

quelques troubles passagers. Si, pour une cause qui reste à déterminer, la

virulence du microbe bactériophage vis-à-vis du microbe pathogène ne se

manifeste pas d’emblée ou ne se manifeste que faiblement, une lutte s’établit

entre les deux organismes, les bacilles dysentériques se multiplient

dans le contenu intestinal, infiltrent la’ muqueuse, la maladie èclate et

l’état du patient enregistre ensuite fidèlement les fluctuations de la lutte.

 

Le microbe bactériophage préexiste dans l’intestin ou il vit narmalement aux dépens du B. coli. Dans les selles normales, son pouvoir antagoniste vis-à-vis de ce dernier bacille est toujours très faible; il peut devenir considérable dans divers états morbides, dans certaines formes d’entérites et de diarrhée banales, par exemple. La présence de bacilles dysentériques dans l’intestin détermine en premier lieu une exaltation considérable de la virulence du microbe bactériophage vis-à-vis du B. coli, puis, par une accoutumance plus ou moins rapide, cette virulence s’exalte vis-à-vis du bacille dysentérique; elle atteint d’emblée ou graduellement une puissance considérable amenant la disparition rapide ou graduelle du bacille pathogène. Si la virulence du microbe bactériophage s’exalte d’emblée, les bacilles dysentériques sont détruits dès le début de leur culture dans le contenu intestinal, la maladie avorte avant tout symptôme ou se borne à quelques troubles passagers. Si, pour une cause qui reste à déterminer, la virulence du microbe bactériophage vis-à-vis du microbe pathogène ne se manifeste pas d’emblée ou ne se manifeste que faiblement, une lutte s’établit entre les deux organismes, les bacilles dysentériques se multiplient dans le contenu intestinal, infiltrent la’ muqueuse, la maladie èclate et l’état du patient enregistre ensuite fidèlement les fluctuations de la lutte.

The microbe bacteriophage pre-exists in the intestine where it normally lives at the expense of B. coli. In normal stool, his antagonist power vis-à-vis the latter bacillus is still very low; it can become considerable in various disease states, in some forms of enteritis and diarrhea mundane, for example. The presence of dysentery bacilli in the intestine first determines considerable exaltation of the virulence of the microbe bacteriophage vis-à-vis the B. coli, and by a more or less rapid habituation, this virulence exalts vis-à -vis the dysentery bacillus; she reached immediately or gradually considerable power causing the rapid or gradual disappearance of pathogenic bacillus. If the virulence of the microbe bacteriophage exalts the outset, the dysentery bacilli are destroyed at the beginning of their culture in the intestinal contents, disease aborted before any symptoms or merely some temporary disturbance. If, for reasons yet to be determined, the virulence of the bacteriophage vis-à-vis the pathogen microbe does not manifest itself immediately or appears only faintly, a struggle takes place between the two organizations, dysentery bacilli multiply in the intestinal content, infiltrate the mucosal, the disease breaks out and the patient then records faithfully the fluctuations of the struggle.

 

En résumé, la pathogénie et la pathologie de la dysenterie pacillaire sont

dominées par deux facteurs agissant en sens contraire: le bacille dysentérique,

agent pathogène, et le microbe filtrant bactériophage, agent d’immunité.

 

En résumé, la pathogénie et la pathologie de la dysenterie pacillaire sont dominées par deux facteurs agissant en sens contraire: le bacille dysentérique, agent pathogène, et le microbe filtrant bactériophage, agent d’immunité.

In summary, the pathogenesis and pathology of dysentery pacillaire are dominated by two factors working in opposite directions: the dysentery bacillus, pathogen, and the filter microbe bacteriophage immunity agent.

 

Comme corollaire, l’expérimentation sur le lapin montre que les cultures

du microbe bactériophage jouissent d’un pouvoir préventif et curatif

dans la maladie expérimentale; d’autre part, le microbe bactériophage se

trouve invariablement présent dans l’intestin des malades dès que les symptômes s’amendent; il semble donc logique de proposer comme traitement

de la dysenterie bacillaire l’administration, dès l’apparition des premiers

symptômes, de cultures actives du microbe bactériophage.

 

Comme corollaire, l’expérimentation sur le lapin montre que les cultures du microbe bactériophage jouissent d’un pouvoir préventif et curatif dans la maladie expérimentale; d’autre part, le microbe bactériophage se trouve invariablement présent dans l’intestin des malades dès que les symptômes s’amendent; il semble donc logique de proposer comme traitement de la dysenterie bacillaire l’administration, dès l’apparition des premiers symptômes, de cultures actives du microbe bactériophage.

As a corollary, testing on rabbits showed that cultures of bacteriophage microbe enjoy a preventive and curative power in the experimental disease; secondly, the microbe bacteriophage is consistently present in the intestine of patients as soon as symptoms make amends; so it seems logical to propose as a treatment for shigellosis administration, from the onset of symptoms, active cultures of the microbe bacteriophage.

 

 

 

Archaeal Virus as Cat Toy

Stephen T. Abedon

Department of Microbiology – The Ohio State University

phage.org – phage-therapy.org – biologyaspoetry.org


 

This post is/was inspired by Stedman, K. M., M. DeYoung, M. Saha, M. B. Sherman, and M. C. Morais. 2015. Structural insights into the architecture of the hyperthermophilic fusellovirus SSV1. Virology 474:105-109. (ncbi.nlm.nih.gov/pubmed/25463608)

Turns out this spindle-shaped virus of Sulfolobus, potentially resembling “two fused fullerene cones”, is an almost perfect prolate spheroid, which (apparently) is the shape of a pig’s bladder, which in turn is the shape of the American football.

The virus itself, however, possesses a “hexameric tail”, which sort of looks like streamers emanating from one end of the “football”. And that, in turn, sure looks an awful lot like this, particularly were the tail trimmed:

http://www.entirelypets.com/jw-pet-cataction-football-streamers.html

“Art” imitates life belongs to cats!

For my renderings on this subject – archaeal virus as football – see:

https://www.facebook.com/pages/Bacteriophage-Ecology-Group/111721928901953

 

 

Virologica Sinica special issue on “Phages and Therapy”

Note: Open access to this special issue no longer appears to be available…

2015, Volume 30, Issue 1

EDITORIAL

Bacteriophages, revitalized after 100 years in the shadow of antibiotics [pubmed]
Hongping Wei
In this issue, readers will not only find that bacteriophage research is a booming field but also learn about the diverse applications currently being explored for bacteriophages. The biggest driving force behind these applications is the serious threat of bacterial antibiotic resistance that is emerging in the current era.

REVIEWS

Bacteriophage secondary infection [pubmed]
Stephen T Abedon
Phages are credited with having been first described in what we now, officially, are commemorating as the 100th. anniversary of their discovery. Those one-hundred years of phage history have not been lacking in excitement, controversy, and occasional convolution. One such complication is the concept of secondary infection, which can take on multiple forms with myriad consequences. The terms secondary infection and secondary adsorption, for example, can be used almost synonymously to describe virion interaction with already phage-infected bacteria, and which can result in what are described as superinfection exclusion or superinfection immunity. The phrase secondary infection also may be used equivalently to superinfection or coinfection, with each of these terms borrowed from medical microbiology, and can result in genetic exchange between phages, phage-on-phage parasitism, and various partial reductions in phage productivity that have been termed mutual exclusion, partial exclusion, or the depressor effect. Alternatively, and drawing from epidemiology, secondary infection has been used to describe phage population growth as that can occur during active phage therapy as well as upon phage contamination of industrial ferments. Here primary infections represent initial bacterial population exposure to phages while consequent phage replication can lead to additional, that is, secondary infections of what otherwise are not yet phage-infected bacteria. Here I explore the varying meanings and resultant ambiguity that has been associated with the term secondary infection. I suggest in particular that secondary infection, as distinctly different phenomena, can in multiple ways infl uence the success of phage-mediated biocontrol of bacteria, also known as, phage therapy.

Bacteriophage therapy against Enterobacteriaceae [pubmed]
Youqiang Xu, Yong Liu, Yang Liu, Jiangsen Pei, Su Yao, Chi Cheng
The Enterobacteriaceae are a class of gram-negative facultative anaerobic rods, which can cause a variety of diseases, such as bacteremia, septic arthritis, endocarditis, osteomyelitis, lower respiratory tract infections, skin and soft-tissue infections, urinary tract infections, intra-abdominal infections and ophthalmic infections, in humans, poultry, animals and fi sh. Disease caused by Enterobacteriaceae cause the deaths of millions of people every year, resulting in enormous economic loss. Drug treatment is a useful and effi cient way to control Enterobacteriaceae infections. However, with the abuse of antibiotics, drug resistance has been found in growing number of Enterobacteriaceae infections and, as such, there is an urgent need to find new methods of control. Bacteriophage therapy is an efficient alternative to antibiotics as it employs a different antibacterial mechanism. This paper summarizes the history of bacteriophage therapy, its bacterial lytic mechanisms, and the studies that have focused on Enterobacteriaceae and bacteriophage therapy.

Survival and proliferation of the lysogenic bacteriophage CTXΦ in Vibrio cholerae [pubmed]
Fenxia Fan, Biao Kan
The lysogenic phage CTXΦ of Vibrio cholerae can transfer the cholera toxin gene both horizontally (inter-strain) and vertically (cell proliferation). Due to its diversity in form and species, the complexity of regulatory mechanisms, and the important role of the infection mechanism in the production of new virulent strains of V. cholerae, the study of the lysogenic phage CTXΦ has attracted much attention. Based on the progress of current research, the genomic features and their arrangement, the host-dependent regulatory mechanisms of CTXΦ phage survival, proliferation and propagation were reviewed to further understand the phage’s role in the evolutionary and epidemiological mechanisms of V. cholerae.

Phage lytic enzymes: a history [pubmed]
David Trudil
There are many recent studies regarding the efficacy of bacteriophage-related lytic enzymes: the enzymes of ‘bacteria-eaters’ or viruses that infect bacteria. By degrading the cell wall of the targeted bacteria, these lytic enzymes have been shown to efficiently lyse Gram-positive bacteria without affecting normal fl ora and non-related bacteria. Recent studies have suggested approaches for lysing Gram-negative bacteria as well (Briersa Y, et al., 2014). These enzymes include: phage-lysozyme, endolysin, lysozyme, lysin, phage lysin, phage lytic enzymes, phageassociated enzymes, enzybiotics, muralysin, muramidase, virolysin and designations such as Ply, PAE and others. Bacteriophages are viruses that kill bacteria, do not contribute to antimicrobial resistance, are easy to develop, inexpensive to manufacture and safe for humans, animals and the environment. The current focus on lytic enzymes has been on their use as anti-infectives in humans and more recently in agricultural research models. The initial translational application of lytic enzymes, however, was not associated with treating or preventing a specifi c disease but rather as an extraction method to be incorporated in a rapid bacterial detection assay (Bernstein D, 1997).The current review traces the translational history of phage lytic enzymes-from their initial discovery in 1986 for the rapid detection of group A streptococcus in clinical specimens to evolving applications in the detection and prevention of disease in humans and in agriculture.

RESEARCH ARTICLES

Selection of phages and conditions for the safe phage therapy against Pseudomonas aeruginosa infections [pubmed]
Victor Krylov, Olga Shaburova, Elena Pleteneva, Sergey Krylov, Alla Kaplan, Maria Burkaltseva, Olga Polygach, Elena Chesnokova
The emergence of multidrug-resistant bacterial pathogens forced us to consider the phage therapy as one of the possible alternative approaches to treatment. The purpose of this paper is to consider the conditions for the safe, long-term use of phage therapy against various infections caused by Pseudomonas aeruginosa. We describe the selection of the most suitable phages, their most effective combinations and some approaches for the rapid recognition of phages unsuitable for use in therapy. The benefi ts and disadvantages of the various different approaches to the preparation of phage mixtures are considered, together with the specifi c conditions that are required for the safe application of phage therapy in general hospitals and the possibilities for the development of personalized phage therapy.

Molecular dissection of phage lysin PlySs2: integrity of the catalytic and cell wall binding domains is essential for its broad lytic activity [pubmed]
Yanling Huang, Hang Yang, Junping Yu, Hongping Wei
The novel phage lysin PlySs2, is reported to be highly active against various bacteria, including staphylococci, streptococci and Listeria. However, the molecular mechanisms underlying its broad lytic spectrum remain to be established. In the present study, the lytic activity of the catalytic domain (CD, PlySc) and binding specificity of the cell wall binding domain (CBD, PlySb) of PlySs2 were examined. Our results showed that PlySc alone maintains very limited lytic activity. Enhanced green fluorescent protein (EGFP)-fused PlySb displayed high binding affinity to the streptococcal strains tested, including S. suis, S. dysgalactiae, and S. agalactiae, but not staphylococci, supporting its utility as a good CBD donor for streptococcal-targeted lysin engineering. EGFP-fused intact PlySs2 similarly displayed high affinity for streptococci, but not staphylococci. Notably, four truncated PlySb fragments showed no binding capacity. These fi ndings collectively indicate that integrity of the PlySc and PlySb domains is an essential determinant of the broad lytic activity of PlySs2.

Isolation and characterization of glacier VMY22, a novel lytic cold-active bacteriophage of Bacillus cereus [pubmed]
Xiuling Ji, Chunjing Zhang, Yuan Fang, Qi Zhang, Lianbing Lin, Bing Tang, Yunlin Wei
As a unique ecological system with low temperature and low nutrient levels, glaciers are considered a “living fossil” for the research of evolution. In this work, a lytic cold-active bacteriophage designated VMY22 against Bacillus cereus MYB41-22 was isolated from Mingyong Glacier in China, and its characteristics were studied. Electron microscopy revealed that VMY22 has an icosahedral head (59.2 nm in length, 31.9 nm in width) and a tail (43.2 nm in length). Bacteriophage VMY22 was classifi ed as a Podoviridae with an approximate genome size of 18 to 20 kb. A one-step growth curve revealed that the latent and the burst periods were 70 and 70 min, respectively, with an average burst size of 78 bacteriophage particles per infected cell. The pH and thermal stability of bacteriophage VMY22 were also investigated. The maximum stability of the bacteriophage was observed to be at pH 8.0 and it was comparatively stable at pH 5.0-9.0. As VMY22 is a cold-active bacteriophage with low production temperature, its characterization and the relationship between MYB41-22 and Bacillus cereus bacteriophage deserve further study.

LETTERS

Variation of resistance and infectivity between Pseudomonas fluorescens SBW25 and bacteriophage Ф2 and its therapeutic implications [pubmed]
Hanchen Chen, Guohua Chen
Studies of the coevolutionary dynamics between Pseudomonas fluorescens SBW25 and bacteriophage Ф can explore host resistance and parasite infectivity with applications in the ecological and therapeutic fields.Coevolutionary dynamics determine the efficacy of phage-based therapy. In the study described here, bacterial resistance and phage infectivity fluctuated with culturetime, perhaps resulting from random mutation and temporaladaptation, which reminds us of the necessity toconsider evolutionary mechanisms when applying phageto treat bacterial infections.

A novel transposable Mu-like prophage in Bacillus alcalophilus CGMCC 1.3604 (ATCC 27647) [pubmed]
Junjie Yang, Yimeng Kong, Xuan Li, Sheng Yang
In this letter, we provide evidence for the first transposable prophage BalMu-1 in Bacilli. The transposable prophage (BalMu-1, Genbank No. KP063902 and KP063903) was identified in Bacillus alcalophilus CGMCC 1.3604(ATCC 27647) through high throughput genome sequencing and PCR-dideoxy chain-termination(Sanger) sequencing.

Isolation and characterization of a lytic bacteriophage φKp-lyy15 of Klebsiella pneumoniae [pubmed]
Yinyin Lu, Hongyan Shi, Zhe Zhang, Fang Han, Jinghua Li, Yanbo Sun
In conclusion, the lytic bacteriophage φKp-lyy belonging to the Siphoviridae family specific for K. pneumonia was isolated and characterized. φKp-lyy displayed a short latent period, stability to a wide pH rang, high thermal resistance, and lytic activity toward a relatively broad range of K. pneumonia isolates. Thus, phage φKplyy should be considered as a candidate for inclusion in phage cocktails to control K. pneumoniae-associated nosocomial infections.

Expression and purification of recombinant lyase gp17 from the LSB-1 phage in Escherichia coli [pubmed]
Taiwu Wang, Hui Lin, Lu Zhang, Guorong Huang, Long Wu, Lei Yu, Hongyan Xiong
In this study, we successfully expressed and purified the recombinant gp17 protein from the LSB-1 phage and also confirmed its bacteriostatic effect. Assays also showed that the recombinant enzyme was soluble and had signifi cant lyase effects on the host bacterium, EIEC8401. A preliminary study demonstrated that the enzyme did not have inhibitory effects on other strains (unpublished data), which might indicate that the exclusive antibacterial effect of gp17 on EIEC8401 could have a special significance in practical application in bacterial therapy.

T4-like coliphage φKAZ14 virulent to pathogenic and extended spectrum β-lactamase-producing Escherichia coli of poultry origin [pubmed]
Kaikabo Adamu Ahmad, Abdulkarim Sabo Mohanmmed, Faridah Abas, Sieo Chin Chin
The aim of the present study was to isolate bacteriophages for the pre-harvest biocontrol of APEC 01 and ESBL-producing E. coli in chicken, in order to mitigate the risk of these pathogens to the food chain. Isolation and characterization of the T4-like coliphage KAZ14, lytic to APEC 01 and ESBL-producing E. coli, is reported and discussed.

Isolation and complete genome sequence of a novel virulent mycobacteriophage, CASbig [pubmed]
Tieshan Teng, Junping Yu, Hang Yang, Hongping Wei
In this study, we report the isolation and the complete genome of a novel mycobacteriophage, CASbig, which has an icosahedral head (diameter 50 ± 2 nm) and a long, non-contractile tail (length 160 ± 5 nm) with transverse striations, ending in a small knob. The length of the tail includes the middle of the baseplate, and the head measurements were taken between opposite apices. These characteristics indicate that the phage belongs to the family Siphoviridae morphotypes.

INSIGHT

Experience of the Eliava Institute in bacteriophage therapy [pubmed]
Mzia Kutateladze
The rapid propagation of multidrug resistant bacterial strains is leading to renewed interest in bacteriophage therapy. With challenges in the treatment of bacterial infections, it is essential for people worldwide to understand how alternative approaches, such as bacteriophages, could be used to combat antibiotic resistant bacteria. The Eliava Institute of Bacteriophages, Microbiology and Virology (Tbilisi, Georgia) is arguably the most famous institution in the world focused on the isolation, study, and selection of phages active against a variety of bacterial pathogens.

Phages vs. Potato Soft Rot

Stephen T. Abedon

Department of Microbiology – The Ohio State University

phage.org – phage-therapy.org – biologyaspoetry.org


 

Here’s an interesting news item, from only a couple of years back (April 4, 2013): “Taking a greener approach to managing potato spoilage”

http://www.farmersguardian.com/home/arable/arable-news/taking-a-greener-approach-to-managing-potato-spoilage/54554.article

Here are some quotes:

The innovative, eco-friendly product is called Biolyse and works by using naturally-occurring bacteriophage

APS chief executive Dr Alison Blackwell says now the product is proven to work on a large scale in potatoes, there is potential for it to be rolled out to other areas within the food processing industry.

Dundee-based APS has been developing bacteriophage since 2004.

Three years ago, APS received a Scottish Enterprise Research and Development grant and was then able to work closely with a team from Branston’s Abernethy site in Perthshire, Scotland, to identify the bacteria causing rots and develop a suitable bacteriophage.

Biolyse was launched in the Abernethy factory in November 2011 and rolled out across Branston’s other two sites in Lincolnshire and Somerset in 2012. The product is also used by QV Foods and Albert Bartlett.

There is a consistent five to tenfold reduction in rots pre and post bacteriophage treatment.

Installing the application equipment for Biolyse cost about £10,000 and was fairly simple, according to Kevin Imrie, site manager at Abernethy.

Anybody have any idea how this product currently is doing?

Here is APS Biocontrol’s web site: http://www.advancedpestsolutions.co.uk/

Further reading:

T4-related bacteriophage LIMEstone isolates for the control of soft rot on potato caused by ‘Dickeya solani’

Phage-Mediated Biocontrol of Plant Pathogens (2001 to “current”)

Phage therapy for plant disease control

Bacteriophage Ecology and Plants