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April 15, 2012

Writing center

Bacterial Phage Therapy

Bacterial phage therapy is the use of bacteriophages to treat pathogenic bacterial

infections. Bacteriophages are special viruses that are very specific in the bacteria that they can

kill. This is important because the uses of phages hypothetically are so specific that they won’t

harm the host. The use of phages are becoming more important within society since many

antibiotics are so strong they do more harm than good.

Bacterial phage therapy was founded in 1915 by British bacteriologist Frederick W.

Twort, who found the small organism that can infect bacterial cells and in turn kill them from its

infection. After he found this small virus. Twort decided not to pursue any more research about it

and left it for some other scientist to discover. Felix d'Hérelle in September 3, 1917, was able to

isolate the bacterial phage without any previous knowledge of Frederick W. Twort’s research

which happened two years previously. In August 1919 d'Hérelle successful use of phages on

humans was administered, he was able to cure dysentery, which is a bacterial infection of

intestine and colon.

In 1923 George Eliava, an associate of d'Herelle, was able to found Eliava Institute in

Georgia. This institute has been one of the leaders in phage therapy’s research since its founding.

All these findings of using bacterial phages to heal infections led to a massive pharmaceutical

race between all of the major world powers; this lead many major corporations to invest large

amounts of money on banks on phage therapy, which was considered the new pharmaceutical

future. Unfortunately, in 1939 the discovery of penicillin and the major production of antibiotics

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because of World War Two caused the Western world to forget about phage therapy. However,

with the blockade of information about antibiotics to the eastern world, the USSR and Germany

still researched much about phage therapy for their troops to prevent bacterial infection. The end

of the Second World War and the end of the Cold War truly hurt phage therapy research because

of the spread of antibiotic information. Fortunately,

For 80 years Georgian doctors have been treating local people, including babies

and newborns, with phages. As a result of the development of antibiotic resistance

since the 1950s and an advancement of scientific knowledge, there has been

renewed interest worldwide in the ability of phage therapy to eradicate bacterial

infections and chronic polymicrobial biofilm, along with other strategies.

(Brussow 2005)

The Georgian doctors have been keeping phage therapy alive ever since 1923 and this has been

very influential now during our time where more and more bacteria are gaining resistance to our

antibiotics. Now with dangerous and controversial antibiotics being used more and more the

need for a safer way to take care of these super strains of bacteria are necessary.

The main types of bacteriophage are used and research either for human or agricultural reasons

are Enterobacteria phage T4/T5/T7. The way the bacteriophage affects the bacteria is during

replication which can be defined in four steps. Attachment, integration, synthesis, and release

these steps all happen in the to bacteriophage life cycles.

Bacteriophages have a lytic cycle or a lysogenic cycle; some of the phages may even

have both cycles if needed for its environment. The first cycle is the lytic cycle: “bacterial cells

are broken open and destroyed after immediate replication of the virion. As soon as the cell is

destroyed, the phage progeny can find new hosts to infect. Lytic phages are more suitable for

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phage therapy. The second cycle is lysogenic pathway: where the viral dna is integrated into the

host but doesn’t go through the lytic path since conditions aren’t favorable (Brussow 2005).

These pathways and knowing how the phage interacts with the cell we can now

determine how to effectively infect bacteria.The two major infections that I will be talking about

are Escherichia coli in acute diarrhea in children and E Coli infections within commercial cow

farms:

The World Health Organization estimates that 5 million children die each year as

a consequence of acute diarrhoea(Snyder & Merson, 1982). Escherichia coli is the

cause of a third of cases of childhood diarrhoea in developing and threshold

countries (Albert et al., 1995) and is also the most prominent cause of diarrhoea in

travelers to developing countries (Black, 1990). Due to its malleable genetic

character, E. coli has one of the widest spectra of disease of any bacterial species

(Donnenberg,2002). The recent emergence of E. coli O157 as a major food

pathogen is a lively reminder of its dynamic character. Furthermore, Shigella

species, the cause of dysentery, taxonomically constitute a subspecies of E. coli.

In addition, effective treatment and prevention measures are lacking for E. coli

diarrhoea. The mainstay of treatment is oral rehydration (Bhan et al., 1994). This

simple and inexpensive measure has saved countless lives, but it does

Not influence the natural course of disease and has no intrinsic antibacterial

activity. (Bru¨ssow et.all,2005)

The World Health organization was able to determine that the majority of all acute diarrhea

deaths of children had been as a result of an E.Coli infection in the bowls. From the research they

were able to see many things about the viability of phage therapy for acute diarrhea. The

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experiments that were held to regulate how well phage cocktails worked on humans with

diarrhea used many different strains of phages that were isolated. This was done first by

isolating two major subcategories of E.Coli phages, lambda like Siphoviridae that were isolated

from healthy stool in hospitals and T4-like Myoviridae in children who had acute diarrhea.

These two major groups of E coli helped give the cocktail a larger range host range meaning it

could affect more different strains of E coli in a person’s system therefor helping them get over

the diarrhea faster. The results were astonishing,

Phage administration was associated with a 3 to 8-fold decrease in dysentery

incidence (1to8 vs 6to7 episodes per 1000 children from treatment and placebo

group, respectively). The culture-confirmed incidence was decreased 2?6-fold by

phage application (0?7 vs 1?8 episodes, respectively). Phage exposure also

decreased the incidence of any form of diarrhoea (15 vs 45 episodes per 1000

children 6 to 12 months old in treatment and placebo group, respectively).

This latter observation suggests a protective effect of the anti-Shigella phage

preparation against other serotypes of E. coli. Protective effects were most

pronounced in children younger than 3 years. (Bru¨ssow,2005)

Even with these field changing results there were three major problems that the researches had to

overcome either back when phages were discovered or during the trials practicality, safety, and

clinical versus actual.

The Practicality of phage therapy was first addressed back during the time of Felix

d'Hérelle. The issue was in what form the phage therapy should be administrated in either a

liquid or in a lyophilized form (freeze-dried powder) and how these forms will affect the

medicine’s effectiveness. In the end the lyophilized from was found to be superior. The reason

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for this is that it could be stored in massive quantities in a relatively low amount of volume, the

shelf life was stable in a room temperature room for about fourteen months without losing it

potency, and with the freeze-dried from it could be given orally instead of intravenously (through

veins). The only down side to this form is that in extreme temperatures the phages became too

acidic and became less effective. Even to this day the oral applications of bacteriophages are

used. Even though some techniques have changed such as using gel casuals instead of

lyophilized pills. In these gels capsule pills the bacteriophages are repressed from activation until

they are introduced to the GI tract.

The next concern that need to be address was that of the mutation of the phage itself.

When phage therapy first was performed, many researchers did not know that there were many

different type of phages that just like their bacterial counterparts can adapt with time to

counteract each other. The major players in E coli bacteriophages would be T4/T7/T2 strains.

When these bacteria would mutate and change their binding sites to counter act the phage. The

specific phages that effect that bacteria would also go through an alteration themselves and

enlarging the host range which made them lose some of its specificity so it could infect the

bacteria. Meaning when bacterial host changes some of the phages will change with it to attack

the cell.

The last and most crucial aspect of phage therapy that researchers had to deal with was

safety. The reason that there is so much concern about phage therapy is that when one uses this

bacterial virus it tends to stay within the body for several years. This gives the person added

protection, but also could give the body problems just in case it mutates. The years of research

had shown that these genes didn’t mutate with formation of any toxic genes that could harm us.

The phages were found to be even better than most antibiotics that kill and harm your body

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organs. Also it is extremely cost effective if you look at from an economic point of view. This is

because Bactria can replicate extremely fast and make many phages when harvested.

All of this research being done shows that phage therapy is safe for humans, but still

there are not many companies or countries using them against human infection because of the

chance of mutation. Though we do not like to use it on ourselves we will use them on animals we

eat such as cows. The use of phages on cows led to the same results as they did on humans

except for two exceptions. Researchers found that the use of low dosages of phages at the first

sign of diarrhea was the best way of action since the phages were able to reproduce exponentially

in 30 minutes about ten to the ten of what was put in. In comparison where high dosage did the

something but it not administer in the right time frame it was ineffective. The second difference

the cows had in comparison to the humans is that: “Calves held in a room previously occupied

by phage exposed calves could no longer be infected with the entero-pathogen, coming close to

d’He´relles’s initial idea of ‘infectious protection’ by phages”(Bru¨ssow,2005). This shows that

instead of bacteria gaining resistance to the antibiotic, which normally happens, the cow gains

resistance to the bacteria from the phage.

The use of bacteriophage therapy is becoming more and more prevalent within our

society. Many people do not even know that many of our vegetables, cheese, and other food

products are already treated with bacteriophages. “In August, 2006 the FDA approved LMP-102

as a food additive to target and kill Listeria monocytogenes. LMP-102 was approved for treating

RTE poultry and meat products. In October of that year the FDA approved a product by EBI

using bacteriophages on cheese to kill the Listeria monocytogenes bacteria, giving them GRAS

status (Generally Recognized As Safe). In July 2007, the same bacteriophages were approved for

use on all food products” (FDA et.all 2008). The future that bacteriophage therapy has in store

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for us could be limitless. With the use of stronger and stronger antibiotics on the rise, the need

for a different means of preventing or dealing with infections is need. Also with the added

benefit of being treated with phages, the body can obtain resistance to many strains of E coli and

other bacteria. This could mean that antibiotics would be useless. Even though phage therapy

may be used more and more our children’s children will come to the same problem that phage

therapy and antibiotics are not enough. But we have a long way to go before that happens

because the only place in the world where phage therapy on humans is legal is in Georgia. Soon

the world will have to realize that phage therapy is actually a good means to kill bacterial

infections rather than using harmful antibiotics ( Brussow 2005).

Referance

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Brussow, H. "Phage Therapy: the Escherichia Coli Experience." Microbiology 151.7

(2005): 2133-140. Print.

USA. FDA. FDA GRAS. Web. <http://google2.fda.gov/search?

q=phage+page&spell=1&client=FDAgov&lr=&proxystylesheet=FDAgov&output=xml_no_dtd

&ie=UTF-8&site=FDAgov&access=p>.

Zuber, S., C. Ngom-Bru, C. Barretto, A. Bruttin, H. Brussow, and E. Denou. "Genome

Analysis of Phage JS98 Defines a Fourth Major Subgroup of T4-Like Phages in Escherichia

Coli." Journal of Bacteriology 189.22 (2007): 8206-214. Print.

Abstracts

The specter of antibiotic-resistant bacteria has provoked renewed interest in the possible use of bacteriophagesto control bacterial infections. We argue that clinical application of phage therapy has been heldback by a failure to appreciate the extent to which the pharmacokinetics of self-replicating agents differfrom those of normal drugs. For self-replicating pharmaceutical agents, treatment outcome depends criticallyon various density-dependent thresholds, often with apparently paradoxical consequences. An abilityto predict these thresholds and associated critical time points is a necessity if phage therapy is to become

clinically practicable. (Clin Pharmacol Ther 2000;68:225-30.)The relationship between endemic bacteriophages infecting E. coli O157:H7 (referred to as “phage”) and

levels of shedding of E. coli O157:H7 by cattle was investigated in two commercial feedlots in southern Alberta,Canada. Between May and November 2007, 10 pens of cattle were monitored by collection of pooled fecal pats,water with sediment from troughs, manure slurry from the pen floor, and rectal fecal samples from individualanimals (20 per pen) at two separate times. Bacteriophages infecting E. coli O157:H7 were detected morefrequently (P < 0.001) after 18 to 20 h enrichment than by initial screening and were recovered in 239 of 855samples (26.5% of 411 pooled fecal pats, 23.8% of 320 fecal grab samples, 21.8% of 87 water trough samples,and 94.6% of 37 pen floor slurry samples). Overall, prevalence of phage was highest (P < 0.001) in slurry.Recovery of phage from pooled fecal pats was highest (P < 0.05) in May. Overall recovery did not differ (P >0.10) between fecal grab samples and pooled fecal pats. A higher prevalence of phage in fecal pats or watertrough samples was associated (P < 0.01) with reduced prevalence of E. coli O157:H7 in rectal fecal samples.There was a weak but significant negative correlation between isolation of phage and E. coli O157:H7 in fecalgrab samples (r _ _0.11; P < 0.05). These data demonstrate that the prevalence of phage fluctuates in amanner similar to that described for E. coli O157:H7. Phage were more prevalent in manure slurry than otherenvironmental sources. The likelihood of fecal shedding of E. coli O157:H7 was reduced if cattle in the pen

harbored phage. DOI 10.1128/AEM.02100-08.Phages have been proposed as natural antimicrobial agents to fight bacterial infections inhumans, in animals or in crops of agricultural importance. Phages have also been discussed ashygiene measures in food production facilities and hospitals. These proposals have a longhistory, but are currently going through a kind of renaissance as documented by a spate ofrecent reviews. This review discusses the potential of phage therapy with a specific example,

namely Escherichia coli. DOI 10.1099/mic.0.27849-0