Reinvevtion of Phage Therapy

7/31/2019 Reinvevtion of Phage Therapy

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Acknowledgement:I am Gurpreet Kaur , the student of M.Sc.(hons) microbio-M.Phil seel highly inducted to

the person cooperated with me during my work The person to whom I am highly thankful

for his expert guidance is DR: RAVINDER SINGH NAGPAL.

I could not express my feelings in words for love, effection ,

blessing rended by my parents.

Above all I highly inducted to God without whose grace this

little work could never seen the light of the day.


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Summary:

It is the method of antibacterial treatment that harnesses the bacteria killing properties of

otherwise harmless viruses or other parts. Phage therapy is use to treat antibiotic

resistant bacteria. There fore, they are preferred over antibiotics. Along with humans it

alsohelps in bio-control of bacteria in food and feed. Phage therapy is widely used to

Vancomycin resistence Enterococcus in experimental mice. Phage therapy is also used to

treat Staphylococcal skin disease. Various diseases caused by Pseudomonas aeruginose

by administerating KPPIO/X3/d orally. Bacteriophages lytic cycle which means that the

phage destroys its life cycle without integerating into host genome. The take up metabolic

machinery of bacteria and lysis the cell wall and results in death of bacteria. Now phages

are widely use in the bio-control of food and feed.


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Now, phages are considered to be the future of microbiology.

These are preferred over the antibiotics because they have low probability of developing

resistence.

What are bacteriophages?

lBacteriophages (viruses that infect bacteria) are fascinating organisms that have playedand continue to play a key role in bacterial genetics and molecular biology. Phage canconfer key phenotypes on their host, for example converting a non-pathogenic strain intoa pathogen, and they play a key role in regulating bacterial populations in all sorts of environments. The phage-bacterium relationship varies enormously: from the simplepredator-prey model to a complex, almost symbiotic relationship that promotes thesurvival and evolutionary success of both. While infection of bacteria used in thefermentation industry can be very problematic and result in financial losses, in other senarios phage infection of bacteria can be exploited for industrial and/or medicalapplications. In fact interest in phage and phage gene products as potential therapeuticagents is increasing rapidly and is likely to have a profound impact on thepharmaceutical industry and biotechnology in general over the coming years. Onepotential application is the use of phage to combat the growing menace of antibiotic-resistant inf .

A bacteriophage (from ' bacteria ' and Greek phagein "to eat") is any one of anumber of viruses that infect bacteria. The term is commonly used in its shortened form,

phage.

Typically, bacteriophages consist of an outer protein hull enclosing genetic material . Thegenetic material can be ssRNA (single stranded RNA), dsRNA , ssDNA , or dsDNA

between 5 and 500 kilo base pairs long with either circular or linear arrangement.Bacteriophages are much smaller than the bacteria they destroy - usually between 20 and200 nm in size.
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Phages are estimated to be the most widely distributed and diverse entities in the biosphere .[1] Phages are ubiquitous and can be found in all reservoirs populated by bacterial hosts, such as soil or the intestines of animals. One of the densest naturalsources for phages and other viruses is sea water, where up to 910 8 virions per milliliter have been found in microbial mats at the surface, [2] and up to 70% of marine bacteria may

be infected by phages.
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ORDER FAMILY Nucleic acid

Siphoviridae Non-enveloped, long non-contractile tailLinear dsDNA

Podoviridae Non-enveloped, shortnoncontractile tailLinear dsDNA

Tectiviridae Non-enveloped, isometric Linear dsDNA

Corticoviridae Non-enveloped, isometric Circular dsDNA

Lipothrixviridae Enveloped, rod-shaped Linear dsDNA

Plasmaviridae Enveloped, pleomorphic Circular dsDNA

Rudiviridae Non-enveloped, rod-shapedLinear dsDNA

Fuselloviridae Non-enveloped, lemon-shapedCircular dsDNA

Inoviridae Non-enveloped,filamentousCircular ssDNA

Microviridae Non-enveloped, isometric Circular ssDNA

Leviviridae Non-enveloped, isometric Linear ssRNA

Segmented
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The linear double-stranded DNA bacteriophage lambda genome contains about 50,000nucleotide pairs and encodes 50-60 different proteins. When the lambda DNA enters thecell the ends join to form a circular DNA molecule. The bacteriophage can multiply in E.coli by a lytic pathway, which destroys the cell, or it can enter a latent prophage state.

Damage to a cell carrying a lambda prophage induces the prophage to exit from the hostchromosome and shift to lytic growth (green arrows). The entrance and exit of thelambda DNA from the bacterial chromosome are site-specific recombination events.
http://en.wikipedia.org/wiki/Cystoviridae


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Phage therapy:

Phage therapy is the therapeutic use of lytic bacteriophages to treat pathogenicbacterial infections. Phage therapy is an alternative to antibiotics being developedfor clinical use by research groups in Eastern Europe and the U.S. After havingbeen extensively used and developed mainly in former Soviet Union countries for about 90 years, phage therapies for a variety of bacterial and poly microbialinfections are now becoming available on an experimental basis in food science andagriculture.

U.S. Th An important benefit of phage therapy is derived other countries, including the eprinciples of phage therapy have potential applications not only in human medicine,but also in dentistry, veterinary science, from the observation that bacteriophagesare much more specific than most antibiotics that are in clinical use. Theoretically,phage therapy is harmless to the eucaryotic host undergoing therapy, and it shouldnot affect the beneficial normal flora of the host. Phage therapy also has few, if any,side effects, as opposed to drugs, and does not stress the liver. Since phages areself-replicating in their target bacterial cell, a single, small dose is theoreticallyefficacious. On the other hand, this specificity may also be disadvantageousbecause a specific phage will only kill a bacterium if it is a match to the specificsubspecies. Thus, phage mixtures may be applied to improve the chances of success, or clinical samples can be taken and an appropriate phage identified andgrown.

Phages are currently being used therapeutically to treat bacterial infections that donot respond to conventional antibiotics, particularly in the country of Georgia. Theyare reported to be especially successful where bacteria have constructed a biofilmcomposed of a polysaccharide matrix that antibiotics cannot penetrate.

. Phage therapy has many potential applications in human medicine as well as dentistry ,veterinary science , and agriculture .[1] If the target host of a phage therapy treatment is notan animal , however, then the term " biocontrol " (as in phage-mediated biocontrol of

bacteria) is sometimes employed rather than "phage therapy".

An important theoretical benefit of phage therapy is that bacteriophages can be muchmore specific than more common drugs , so can be chosen to be harmless to not only thehost organism (human, animal, or plant ), but also other beneficial bacteria , such as gut flora , reducing the chances of opportunistic infections . They also have a high therapeutic index , that is, phage therapy gives rise to few if any side effects , as opposed to drugs, anddoes not stress the liver . Because phages replicate in vivo , a smaller effective dose can beused. On the other hand, this specificity is also a disadvantage: A phage will only kill a
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bacterium if it is a match to the specific strain . Thus, phage mixtures are often applied toimprove the chances of success, or samples can be taken and an appropriate phageidentified and grown.

Phages are currently being used therapeutically to treat bacterial infections that do not

respond to conventional antibiotics, particularly in the country of Georgia .[2][3] [4]

Theytend to be more successful than antibiotics where there is a biofilm covered by a polysaccharide layer, which antibiotics typically cannot penetrate. [citation needed ] In the West,no therapies are currently authorized for use on humans , although phages for killing food

poisoning bacteria ( Listeria ) are now in use. [5]

HISTORY:

Following the discovery of bacteriophages by Frederick Twort and Felix d'Hrelle[6]

in1915 and 1917, phage therapy was immediately recognized by many to be a key wayforward for the eradication of bacterial infections. A Georgian, George Eliava , wasmaking similar discoveries. He travelled to the Pasteur Institute in Paris where he metd'Hrelle, and in 1926 he founded the Eliava Institute in Tbilisi , Georgia , devoted to thedevelopment of phage therapy.

In neighbouring countries including Russia , extensive research and development soon began in this field. In the USA during the 1940s, commercialization of phage therapy wasundertaken by the large pharmaceutical company, Eli Lilly .

Whilst knowledge was being accumulated regarding the biology of phages and how touse phage cocktails correctly, early uses of phage therapy were often unreliable. Whenantibiotics were discovered in 1941 and marketed widely in the USA and Europe,Western scientists mostly lost interest in further use and study of phage therapy for sometime. [7]

Isolated from Western advances in antibiotic production in the 1940s, Russian scientistscontinued to develop already successful phage therapy to treat the wounds of soldiers infield hospitals . During World War II , the Soviet Union used bacteriophages to treat manysoldiers infected with various bacterial diseases e.g. dysentery and gangrene. The successrate was as good as, if not better than any antibiotic. [citation needed ] Russian researchers

continued to develop and to refine their treatments and to publish their research andresults. However, due to the scientific barriers of the Cold War , this knowledge was nottranslated and did not proliferate across the world. [8][9]

There is an extensive library and research center at the Eliava Institute in Tbilisi, Georgia.Phage therapy is today a widespread form of treatment in neighbouring countries. For 80years Georgian doctors have been treating local people, including babies and newborns,with phages.
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As a result of the development of antibiotic resistance since the 1950s and anadvancement of scientific knowledge, there is renewed interest worldwide in the abilityof phage therapy to eradicate bacterial infections and chronic polymicrobial biofilm,along with other strategies.

Phages have been explored as means to eliminate pathogens like Campylobacter in rawfood [10] and Listeria in fresh food or to reduce food spoilage bacteria. [11] In agricultural practice phages were used to fight pathogens like Campylobacter , Escherichia andSalmonella in farm animals, Lactococcus and Vibrio pathogens in fish from aquacultureand Erwinia and Xanthomonas in plants of agricultural importance. The oldest use was,however, in human medicine. Phages were used against diarrheal diseases caused by E. coli , Shigella or Vibrio and against wound infections caused by facultative pathogens of the skin like staphylococci and streptococci . Recently the phage therapy approach has

been applied to systemic and even intracellular infections and the addition of non-replicating phage and isolated phage enzymes like lysins to the antimicrobial arsenal.However, definitive proof for the efficiency of these phage approaches in the field or the

hospital is only provided in a few cases.[11]

Some of the interest in the West can be traced back to 1994, when Soothill demonstrated(in an animal model) that the use of phages could improve the success of skin grafts byreducing the underlying Pseudomonas aeruginosa infection. [12] Recent studies have

provided additional support for these findings. [13]

Recently, the use of phages as delivery mechanisms for traditional antibiotics has been proposed. [14][ 15] The use of phages to deliver antitumor agents has also beendescribed, in preliminary in vitro experiments for cells in tissue culture. [16]

Potential benefits :A potential benefit of phage therapy is freedom from the severe adverse effects of antibiotics. Also it would possibly be fast-acting, once the exact bacteria are identifiedand the phages administered. Another benefit of phage therapy is that although bacteria are able to develop resistance to phages the resistance might be easier to overcome.

Bacteriophages are often very specific, targeting only one or a few strains of bacteria. [17]

Traditional antibiotics usually have more wide-ranging effect, killing both harmful bacteria and useful bacteria such as those facilitating food digestion. The specificity of

bacteriophages might reduce the chance that useful bacteria are killed when fighting aninfection.

Increasing evidence shows the ability of phages to travel to a required site includingthe brain, where the blood brain barrier can be crossed and multiply in the presence of an appropriate bacterial host, to combat infections such as meningitis . However the

patient's immune system can, in some cases mount an immune response to the phage (2out of 44 patients in a Polish trial [18]). This might possibly be therapeutically significant.
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Development and production is faster than antibiotics , on condition that the requiredrecognition molecules are known. [citation needed ]

Research groups in the West are engineering a broader spectrum phage and also targetMRSA treatments in a variety of forms - including impregnated wound dressings,

preventative treatment for burn victims, phage-impregnated sutures. Enzobiotics are anew development at Rockefeller University that create enzymes from phage. These show potential for preventing secondary bacterial infections e.g. pneumonia developing with patients suffering from flu, otitis etc.. [citation needed ]

Some bacteria such as multiply resistant Klebsiella pneumoniae have no non toxicantibiotics available, and yet killing of the bacteria via intraperitoneal, intravenous or intranasal of phages in vivo has been shown to work in laboratory tests.

Application

Collection :In its simplest form, phage treatment works by collecting local samples of water likely tocontain high quantities of bacteria and bacteriophages, for example effluent outlets,sewage and other sources .[2] They can also be extracted from corpses. The samples aretaken and applied to the bacteria that are to be destroyed which have been cultured ongrowth medium.

The bacteria usually die, and the mixture is centrifuged. The phages collect on the top of

the mixture and can be drawn off.

The phage solutions are then tested to see which ones show growth suppression effects(lysogeny) and/or destruction (lysis) of the target bacteria. The phage showing lysis arethen amplified on cultures of the target bacteria, passed through a filter to remove all butthe phages, then distributed.

Treatment :Phages are "bacterium specific" and it is therefore necessary in many cases to take a swabfrom the patient and culture it prior to treatment. Occasionally, isolation of therapeutic

phages can typically require a few months to complete, but clinics generally keepsupplies of phage cocktails for the most common bacterial strains in a geographical area.

Phages in practice are applied orally, topically on infected wounds or spread ontosurfaces, or used during surgical procedures. Injection is rarely used, avoiding any risks
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of trace chemical contaminants that may be present from the bacteria amplificationstage,and recognizing that the immune system naturally fights against viruses introducedinto the bloodstream or lymphatic system.

The direct human use of phage might possibly be safe; suggestively, in August 2006, the

United States Food and Drug Administration approved spraying meat with phages.Although this initially raised concerns since without mandatory labeling consumers won't be aware that meat and poultry products have been treated with the spray, [20] it confirmsto the public that, for example, phages against Listeria are generally recognized as safe(GRAS status) within the worldwide scientific community and opens the way for other

phages to also be recognized as having GRAS status.

Phage therapy has been attempted for the treatment of a variety of bacterial infectionsincluding: laryngitis , skin infections, dysentery , conjunctivitis , periodontitis , gingivitis ,sinusitis , urinary tract infections and intestinal infections, burns, boils, etc. [2] - also poly-microbial biofilms on chronic wounds, ulcers and infected surgical sites. [citation needed ]

In 2007, Phase 2a clinical trials have been reported at the Royal National Throat, Nose and Ear Hospital , London for Pseudomonas aeruginosa infections ( otitis ).[21] .[22][ 23]

Documentation of the Phase-1 and Phase-2a study is not available at present.

Phase 1 clinical trials are underway in the South West Regional Wound Care Center,Lubbock, Texas for an approved cocktail of phages against bacteria, including P.aeruginosa , Staphylococcus aureus and Escherichia coli (better known as E. coli). [citationneeded ]

Reviews of phage therapy indicate that students should aware of this.

Distribution :Phages can usually be freeze dried and turned into pills without materially impactingefficacy. [2] In pill form temperature stability up to 55 C, and shelf lives of 14 months have

been shown.

Other forms of administration can include application in liquid form. These vials areusually best kept refrigerated. [ Oral administration works better when an antacid isincluded, as this increases the number of phages surviving passage through the

stomachTopical administration often involves application to gauzes that are laid on thearea to be treated

Obstacles :General
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The host specificity of phage therapy may make it necessary for clinics to make differentcocktails for treatment of the same infection or disease because the bacterial componentsof such diseases may differ from region to region or even person to person. Such a

process would make it difficult for large scale production of phage therapy. Additionally, patent issues (specifically on living organisms) may complicate distribution for

pharmaceutical companies wishing to have exclusive rights over their "invention";making it unlikely that a for-profit corporation will invest capital in the widespreadapplication of this technology.

In addition, due to the specificity of individual phages, for a high chance of success, amixture of phages is often applied. This means that 'banks' containing many different

phages are needed to be kept and regularly updated with new phages, which makesregulatory testing for safety harder and more expensive.

Some bacteria, for example Clostridium and Mycobacterium , have no known therapeutic phages available as yet.

To work, the virus has to reach the site of the bacteria, and viruses do not necessarilyreach the same places that antibiotics can reach.

Funding for phage therapy research and clinical trials is generally insufficient anddifficult to obtain, since it is a lengthy and complex process to patent bacteriophage

products. Scientists comment that 'the biggest hurdle is regulatory', whereas an officialview is that individual phages would need proof individually because it would be toocomplicated to do as a combination, with many variables. Due to the specificity of

phages, phage therapy would be most effective with a cocktail injection, which aregenerally rejected by the FDA . Researchers and observers predict that for phage therapy

to be successful the FDA must change its regulatory stance on combination drugcocktails. Public awareness and education about phage therapy are generally limited toscientific or independent research rather than mainstream media. The negative public

perception of viruses may also play a role in the reluctance to embrace phage therapy

Safety :Phage therapy is generally considered safe. As with antibiotic therapy and other methods

of countering bacterial infections, endotoxins are released by the bacteria as they aredestroyed within the patient ( Herxheimer reaction ). This can cause symptoms of fever, or in extreme cases toxic shock (a problem also seen with antibiotics) is possibleJanakiraman Ramachandran, a former president of AstraZeneca India who 2 years agolaunched GangaGen Inc., a phage-therapy start-up in Bangalore, argues that thiscomplication can be avoided in those types of infection where this reaction is likely tooccur by using genetically engineered bacteriophages; which have had their generesponsible for producing endolysin removed. Without this gene the host bacterium still
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dies but remains intact because the lysis is disabled. On the other hand this modificationstops the exponential growth of phages, so one administered phage means one dead

bacterial cell. ] Eventually these dead cells are consumed by the normal house cleaningduties of the phagocytes , which utilise enzymes to break the whole bacterium and itscontents down into its harmless sub-units of proteins, polysaccharides and lipidsCare has

to be taken in manufacture that the phage medium is free of bacterial fragments andendotoxins from the production process.

Lysogenic bacteriophages are not generally used therapeutically. This group can act as away for bacteria to exchange DNA, and this can help spread antibiotic resistance or even,theoretically, can make the bacteria pathogenic (see Cholera ).

The lytic bacteriophages available for phage therapy are best kept refrigerated butdiscarded if the pale yellow clear liquid goes cloudy.

Phage display :1. Phage display is a method for the study of protein-protein, protein-peptide, and

protein-DNA interactions that utilizes bacteriophage to connect proteins with thegenetic information that encodes them. [1] This connection between genotype and

phenotype enables large libraries of proteins to be screened and amplified in a process called in vitro selection, which is analogous to natural selection . The most

common bacteriophages used in phage display are M13 and fd filamentous phage ,[2][3] though T4, T7, and phage have also been used.

Principle :

Like the two-hybrid system , phage display is used for the high-throughput screening of protein interactions. In the case of M13 filamentous phage display, the DNA encodingthe protein or peptide of interest is ligated into the pIII or pVIII gene. Multiple cloning sites are sometimes used to ensure that the fragments are inserted in all three possibleframes so that the cDNA fragment is translated in the proper frame. The phage gene andinsert DNA hybrid is then transformed into E. coli bacterial cells such as TG1 or XL1-Blue E. coli . The phage particles will not be released from the E. coli cells until they areinfected with helper phage , which enables packaging of the phage DNA and assembly of the mature virions with the relevant protein fragment as part of their outer coat on either the minor (pIII) or major (pVIII) coat protein. The incorporation of many different DNAfragments into the pIII or pVIII genes generates a library from which members of interestcan be isolated.
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By immobilising a relevant DNA or protein target(s) to the surface of a well, a phage thatdisplays a protein that binds to one of those targets on its surface will remain while othersare removed by washing. Those that remain can be eluted, used to produce more phage(by bacterial infection with helper phage) and so produce a phage mixture that is enrichedwith relevant (i.e. binding) phage. The repeated cycling of these steps is referred to as

'panning', in reference to the enrichment of a sample of gold by removing undesirablematerials.

Phage eluted in the final step can be used to infect a suitable bacterial host, from whichthe phagemids can be collected and the relevant DNA sequence excised and sequenced toidentify the relevant, interacting proteins or protein fragments.

Recent work published by Chasteen et al., shows that use of the helper phage can beeliminated by using a novel 'bacterial packaging cell line' technology

General protocol :

1. microtiter plate.2. Target proteins or DNA sequences are immobilised to the wells of a Many genetic

sequences are expressed in a bacteriophage library in the form of fusions with the bacteriophage coat protein, so that they are displayed on the surface of the viral particle. The protein displayed corresponds to the genetic sequence within the phage.

3. This phage-display library is added to the dish and after allowing the phage time to bind, the dish is washed.

4. Phage-displaying proteins that interact with the target molecules remain attached tothe dish, while all others are washed away.

5. Attached phage may be eluted and used to create more phage by infection of suitable bacterial hosts. The new phage constitutes an enriched mixture, containingconsiderably less irrelevant (i.e. non-binding phage) than were present in the initialmixture.

6. The DNA within the interacting phage contains the sequences of interacting proteins,and following further bacterial-based amplification, can be sequenced to identify therelevant, interacting proteins or protein fragments.

Applications :The applications of this technology include determination of interaction partners of a

protein (which would be used as the immobilised phage "bait" with a DNA libraryconsisting of all coding sequences of a cell, tissue or organism) so that new functions or mechanisms of function of that protein may be inferred [5]. The technique is also used todetermine tumour antigens (for use in diagnosis and therapeutic targeting) [6] and insearching for protein-DNA interactions [7] using specially-constructed DNA libraries withrandomised segments.
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Phage display is also a widely used method for in vitro protein evolution (also called protein engineering ). As such, phage display is a useful tool in drug discovery . It is usedfor finding new ligands (enzyme inhibitors, receptor agonists and antagonists) to target

proteinsCompeting methods for in vitro protein evolution are yeast display , bacterial display , ribosome display , and mRNA display .

The treatment of infectious diseases with antibiotics is becoming increasinglychallenging. Very few new antimicrobials are in the pharmaceutical industry pipeline.One of the potential alternatives for antibiotics is phage therapy. Major obstacles for the

clinical application of bacteriophages are a false perception of viruses as enemies of lifeand the lack of a specific frame for phage therapy in the current Medicinal ProductRegulation. Short-term borderline solutions under the responsibility of a Medical EthicalCommittee and/or under the umbrella of the Declaration of Helsinki are emerging. As along-term solution, however, we suggest the creation of a specific section for phagetherapy under the Advanced Therapy Medicinal Product Regulation to papain yields

potent peptide inhibitors of

cathepsins L, B, H, and K"

Bacteria-Eating Virus Approved asFood Additive:

Not all viruses harm people. The Food and Drug Administration has approved a mixtureof viruses as a food additive to protect people. The additive can be used in processingplants for spraying onto ready-to-eat meat and poultry products to protect consumersfrom the potentially life-threatening bacterium Listeria monocytogenes (L.monocytogenes ).

The viruses used in the additive are known as bacteriophages. Bacteriophage means"bacteria eater." A bacteriophage, also called a phage (pronounced fayj), is any virusthat infects bacteria.

Consuming food contaminated with the bacterium L. monocytogenes can cause aninfectious disease, listeriosis, which is rarely serious in healthy adults and children, butcan be severe and even deadly in pregnant women , newborns, older people, and peoplewith weakened immune systems. Pregnant women are about 20 times more likely than
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other healthy adults to get listeriosis, according to the Centers for Disease Control andPrevention (CDC). Listeriosis can cause miscarriage, stillbirth, premature delivery, or death of a newborn baby.

People with listeriosis have fever and muscle aches, and sometimes an upset stomach,nausea, and diarrhea. If the infection spreads to the nervous system, headache, stiff neck, confusion, loss of balance, or convulsions can occur.

The CDC estimates that about 2,500 people become seriously ill with listeriosis eachyear in the United States. Of these, about 500 die.

Cooking can kill L. monocytogenes , but many ready-to-eat foods, such as hot dogs,sausages, luncheon meats, cold cuts, and other deli-style meats and poultry, maybecome contaminated within the processing plant after cooking and before packaging.Unlike fresh meat and poultry, the ready-to-eat products can be consumed withoutreheating, so the L. monocytogenes survive and are ingested.

"L. monocytogenes can continue to thrive even in refrigerated conditions," says Capt. Andrew Zajac, a food safety expert and acting director of the Division of Petition Reviewwithin the FDA's Center for Food Safety and Applied Nutrition (CFSAN). "If a foodproduct contaminated with L. monocytogenes is bought by a consumer and broughthome and refrigerated, the bacteria can continue to multiply."

How Bacteriophages Work? Bacteriophages are found in the environment. "We're routinely exposed tobacteriophages," says Zajac. "They are found in soil and water, and they are part of themicrobial population in the human gut and oral cavity."

Bacteriophages infect only bacteria, says Zajac. "They don't infect plant or mammaliancells." Thousands of varieties of phages exist, and each one infects only one type or afew types of bacteria. The particular phages approved as a food additive are veryspecific to Listeria , says Zajac. "They'll only thrive if Listeria are present."

The type of phage that was approved is lytic, which means that the phage destroys itshost during its life cycle without integrating into the host genome. This type of phageworks by attaching itself to a bacterium and injecting its genetic material into the cell.The phage takes over the metabolic machinery of the bacterium, forcing it to producehundreds of new phages and causing the bacterial cell walls to break open. This processkills the bacterium and releases many new phages, which seek out other bacteria toinvade and repeat the cycle.

"The process continues until all host bacteria have been destroyed," says Zajac. "Thenthe bacteriophages cease replicating. They need a host to multiply and will graduallybecome inactive when they lose the host."


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Approval Process for Food Additives:

To market a new food additive, a manufacturer must petition the FDA for its approval.The petition must provide convincing evidence that the proposed additive performs as itis intended and will not cause harmful effects when consumed.

If an additive is approved, the FDA issues a regulation that includes information on thetypes of foods in which the additive can be used and maximum amounts to be used. Theregulation also provides the additive's identity and specifications on purity, which willensure that the additive used in food is the same substance that was evaluated andapproved by the FDA.

Once a food additive is approved, any company can use the additive, says Zajac, aslong as it meets the conditions in the regulation.

In response to a petition submitted by industry, the FDA published a regulation in August2006 permitting the use of a Listeria -specific bacteriophage preparation on ready-to-eatmeat and poultry products.

The preparation combines six different phages that have been shown to be effective

against 170 different strains of L. monocytogenes . Multiple phages are used so that if the L. monocytogenes develop resistance to several phages, the remaining ones canstill destroy the bacteria.

The FDA must approve any additive before it can be used in food. When an additive is tobe used on meat or poultry products, as with this one, both the FDA and the U.S.Department of Agriculture (USDA) are involved in the approval. The FDA evaluates thesafety of the ingredient for its intended use. At the same time, the USDA evaluates theingredient's suitability.

The FDA's food additive regulations define safety as "a reasonable certainty that thesubstance is not harmful under the intended conditions of use." The FDA's CFSAN

determined that the phage preparation does not pose any safety concerns based, inpart, on published reports submitted by the petitioner on the results of the use of phagesin animal and human studies.

The USDA's Food Safety and Inspection Service (FSIS) evaluated the bacteriophagepreparation's suitability. "Suitability establishes that the use of a substance is effective inperforming the intended purpose of use and at the lowest level necessary for particular types of products," says Robert C. Post, Ph.D., director of the FSIS' Labeling andConsumer Protection Staff. In addition, suitability is an assurance that the use of the


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additive will not result in a product that is unfit for human consumption (adulterated) or one that misleads consumers. Consumers would be misled if, for example, the additivemakes a product "appear to be a better value than it actually is or it masks spoilage,"says Post.

The FSIS evaluated data submitted by the petitioner to ensure suitability for a number of ready-to-eat products, such as sausages, turkey, soups, stews, hot dogs, bologna,Vienna sausage, and cooked ham and turkey .

Labeling:Under the Federal Meat Inspection Act and the Poultry Products Inspection Act, bothadministered by the USDA, the use of the phage preparation must be declared onlabeling as an ingredient. Consumers will see "bacteriophage preparation" on the labelof meat or poultry products that have been treated with the food additive.If consumershave any concerns about what they're getting at the deli counter, says Post, "they

always have the ability to ask for the label of the product being prepared or sliced to seewhat it contains."

A Phage First:This approval marks the first time that the FDA has regulated the use of a phage preparation as afood additive. Phages are currently approved in the United States for pesticide applications, suchas spraying on crops.

Scientists continue to be interested in other uses for phages, such as to prevent foodproducts from contamination with other types of harmful bacteria and to act as possibletreatments for bacterial infections in people.

The efficacy of bacteriophage (phage) therapy by using a murine model of gut-derived sepsis caused by Pseudomonas aeruginosa that closelyresembles the clinical pathophysiology of septicemia in humans. Oraladministration of a newly isolated lytic phage strain (KPP10) significantlyprotected mice against mortality (survival rates, 66.7% for the phage-treatedgroup versus 0% for the saline-treated control group; P


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Bacteriophages are viruses that only infect bacteria. They haveplayed an important role in the development of molecular biology andhave been used as anti-bacterial agents. Since their independent

discovery by Twort and d'Herelle, they have been extensively used toprevent and treat bacterial infections, mainly in Eastern Europe andthe former Soviet Union. In western countries this method has beensporadically employed on humans and domesticated animals.However, the discovery and widespread use of antibiotics, coupledwith doubts about the efficacy of phage therapy, led to an eclipse inthe use of phage in medicine. The emergence of antibiotic resistantbacteria, especially strains that are multiply resistant, has resulted ina renewed interest in alternatives to conventional drugs. One of thepossible replacements for antibiotics is the use of bacteriophages asantimicrobial agents. This brief review aims to describe the history of bacteriophage and early clinical studies on their use in bacterialdisease prophylaxis and therapy, and discuss the advantages anddisadvantages of bacteriophage in this regard.

Exploiting phages for production of vaccines :Bacteriophages have a number of potential applications in the biotechnologyindustry- delivery vehicles for protein and DNA vaccines, for gene therapy, asalternatives to antibiotics, and as protein/antibody library screening tools. Thisdiversity and ease of manipulation and production means they have potentialresearch, therapeutic and manufacturing uses in both the biotechnology andmedical fields. It is hoped that the wide range of scientists, clinicians andbiotechnologists currently researching or putting bacteriophages to practical useare able to pool their knowledge and expertise and thereby accelerate progresstowards further development in this exciting field of biotechnology.


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Conclusion:

whole phage therapy or part therapy are promising . Very rapid and potent antibacterial activity in vitro and vivo against

Gram positive bacteria.

Completely new mode of action and enzymatic cleavage of peptidoglycan .

A narrow antibacterial specterum.

Low probability of developing resistence.

Apparent safety.


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Reference:1. ^ Hufton SE, Moerkerk PT, Meulemans EV, de Brune A, Arends JW,

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