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.
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 played and continue to play a key role in bacterial genetics and molecular biology. Phage can confer key phenotypes on their host, for example converting a non-pathogenic strain into a pathogen, and they play a key role in regulating bacterial populations in all sorts of environments. The phage-bacterium relationship varies enormously: from the simple predator-prey model to a complex, almost symbiotic relationship that promotes the survival and evolutionary success of both. While infection of bacteria used in the fermentation industry can be very problematic and result in financial losses, in other senarios phage infection of bacteria can be exploited for industrial and/or medical applications. In fact interest in phage and phage gene products as potential therapeutic agents is increasing rapidly and is likely to have a profound impact on the pharmaceutical industry and biotechnology in general over the coming years. One potential application is the use of phage to combat the growing menace of antibiotic-resistant inf.
A bacteriophage (from 'bacteria' and Greek φάγειν phagein "to eat") is any one of a number 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. The genetic 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 and 200 nm in size.
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 natural sources for phages and other viruses is sea water, where up to 9×108 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 | | |
| Non-enveloped, long non-contractile tail | Linear dsDNA |
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| Non-enveloped, short noncontractile tail | Linear dsDNA |
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| Non-enveloped, isometric | Linear dsDNA |
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| Non-enveloped, isometric | Circular dsDNA |
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| Enveloped, rod-shaped | Linear dsDNA |
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| Enveloped, pleomorphic | Circular dsDNA |
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| Non-enveloped, rod-shaped | Linear dsDNA |
| |||
| Non-enveloped, lemon-shaped | Circular dsDNA |
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| Non-enveloped, filamentous | Circular ssDNA |
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| Non-enveloped, isometric | Circular ssDNA |
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| Non-enveloped, isometric | Linear ssRNA |
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| Enveloped, spherical | Segmented dsRNA |
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The linear double-stranded DNA bacteriophage lambda genome contains about 50,000 nucleotide pairs and encodes 50-60 different proteins. When the lambda DNA enters the cell 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 host chromosome and shift to lytic growth (green arrows). The entrance and exit of the lambda DNA from the bacterial chromosome are site-specific recombination events.
Phage therapy:
Phage therapy is the therapeutic use of lytic bacteriophages to treat pathogenic bacterial infections. Phage therapy is an alternative to antibiotics being developed for clinical use by research groups in Eastern Europe and the U.S.
U.S. Th
An important benefit of phage therapy is derived other countries, including the e principles of phage therapy have potential applications not only in human medicine, but also in dentistry, veterinary science, from the observation that bacteriophages are much more specific than most antibiotics that are in clinical use. Theoretically, phage therapy is harmless to the eucaryotic host undergoing therapy, and it should not 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 are self-replicating in their target bacterial cell, a single, small dose is theoretically efficacious. On the other hand, this specificity may also be disadvantageous because a specific phage will only kill a bacterium if it is a match to the specific subspecies. Thus, phage mixtures may be applied to improve the chances of success, or clinical samples can be taken and an appropriate phage identified 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
. 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 not an 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 much more specific than more common drugs, so can be chosen to be harmless to not only the host 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, and does not stress the liver. Because phages replicate in vivo, a smaller effective dose can be used. On the other hand, this specificity is also a disadvantage: A phage will only kill a bacterium if it is a match to the specific strain. Thus, phage mixtures are often applied to improve the chances of success, or samples can be taken and an appropriate phage identified 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] They tend 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'Hérelle[6] in 1915 and 1917, phage therapy was immediately recognized by many to be a key way forward for the eradication of bacterial infections. A Georgian, George Eliava, was making similar discoveries. He travelled to the Pasteur Institute in Paris where he met d'Hérelle, and in 1926 he founded the Eliava Institute in Tbilisi, Georgia, devoted to the development 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 was undertaken by the large pharmaceutical company, Eli Lilly.
Whilst knowledge was being accumulated regarding the biology of phages and how to use phage cocktails correctly, early uses of phage therapy were often unreliable. When antibiotics 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 some time.[7]
Isolated from Western advances in antibiotic production in the 1940s, Russian scientists continued to develop already successful phage therapy to treat the wounds of soldiers in field hospitals. During World War II, the Soviet Union used bacteriophages to treat many soldiers infected with various bacterial diseases e.g. dysentery and gangrene. The success rate 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 and results. However, due to the scientific barriers of the Cold War, this knowledge was not translated 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 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 is renewed interest worldwide in the ability of 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 raw food[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 and Salmonella in farm animals, Lactococcus and Vibrio pathogens in fish from aquaculture and 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 by reducing 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 been described, 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 identified and 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 an infection.
Increasing evidence shows the ability of phages to travel to a required site — including the 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 (2 out of 44 patients in a Polish trial[18]). This might possibly be therapeutically significant.
Development and production is faster than antibiotics, on condition that the required recognition molecules are known.[citation needed]
Research groups in the West are engineering a broader spectrum phage and also target MRSA treatments in a variety of forms - including impregnated wound dressings, preventative treatment for burn victims, phage-impregnated sutures. Enzobiotics are a new 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 toxic antibiotics 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 to contain high quantities of bacteria and bacteriophages, for example effluent outlets, sewage and other sources.[2] They can also be extracted from corpses. The samples are taken and applied to the bacteria that are to be destroyed which have been cultured on growth 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 are then amplified on cultures of the target bacteria, passed through a filter to remove all but the phages, then distributed.
Treatment:
Phages are "bacterium specific" and it is therefore necessary in many cases to take a swab from the patient and culture it prior to treatment. Occasionally, isolation of therapeutic phages can typically require a few months to complete, but clinics generally keep supplies 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 onto surfaces, or used during surgical procedures. Injection is rarely used, avoiding any risks of trace chemical contaminants that may be present from the bacteria amplification stage,and recognizing that the immune system naturally fights against viruses introduced into 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 confirms to 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 infections including: 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).[citation needed]
Reviews of phage therapy indicate that students should aware of this.
Distribution:
Phages can usually be freeze dried and turned into pills without materially impacting efficacy.[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 are usually best kept refrigerated.[ Oral administration works better when an antacid is included, as this increases the number of phages surviving passage through the stomachTopical administration often involves application to gauzes that are laid on the area to be treated
Obstacles:
General
The host specificity of phage therapy may make it necessary for clinics to make different cocktails for treatment of the same infection or disease because the bacterial components of 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 widespread application of this technology.
In addition, due to the specificity of individual phages, for a high chance of success, a mixture 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 makes regulatory 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 necessarily reach the same places that antibiotics can reach.
Funding for phage therapy research and clinical trials is generally insufficient and difficult to obtain, since it is a lengthy and complex process to patent bacteriophage products. Scientists comment that 'the biggest hurdle is regulatory', whereas an official view is that individual phages would need proof individually because it would be too complicated 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 are generally rejected by the FDA. Researchers and observers predict that for phage therapy to be successful the FDA must change its regulatory stance on combination drug cocktails. Public awareness and education about phage therapy are generally limited to scientific 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 are destroyed within the patient (Herxheimer reaction). This can cause symptoms of fever, or in extreme cases toxic shock (a problem also seen with antibiotics) is possible Janakiraman Ramachandran, a former president of AstraZeneca India who 2 years ago launched GangaGen Inc., a phage-therapy start-up in Bangalore, argues that this complication can be avoided in those types of infection where this reaction is likely to occur by using genetically engineered bacteriophages; which have had their gene responsible for producing endolysin removed. Without this gene the host bacterium still dies but remains intact because the lysis is disabled. On the other hand this modification stops the exponential growth of phages, so one administered phage means one dead bacterial cell.] Eventually these dead cells are consumed by the normal house cleaning duties of the phagocytes, which utilise enzymes to break the whole bacterium and its contents 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 and endotoxins from the production process.
Lysogenic bacteriophages are not generally used therapeutically. This group can act as a way 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 but discarded if the pale yellow clear liquid goes cloudy.
Phage display:
- Phage display is a method for the study of protein-protein, protein-peptide, and protein-DNA interactions that utilizes bacteriophage to connect proteins with the genetic 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 λ 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 encoding the 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 possible frames so that the cDNA fragment is translated in the proper frame. The phage gene and insert 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 are infected 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 DNA fragments into the pIII or pVIII genes generates a library from which members of interest can be isolated.
By immobilising a relevant DNA or protein target(s) to the surface of a well, a phage that displays a protein that binds to one of those targets on its surface will remain while others are 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 enriched with 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 undesirable materials.
Phage eluted in the final step can be used to infect a suitable bacterial host, from which the phagemids can be collected and the relevant DNA sequence excised and sequenced to identify the relevant, interacting proteins or protein fragments.
Recent work published by Chasteen et al., shows that use of the helper phage can be eliminated 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 to the 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, containing considerably less irrelevant (i.e. non-binding phage) than were present in the initial mixture.
6. The DNA within the interacting phage contains the sequences of interacting proteins, and following further bacterial-based amplification, can be sequenced to identify the relevant, 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 library consisting 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 to determine tumour antigens (for use in diagnosis and therapeutic targeting)[6] and in searching for protein-DNA interactions[7] using specially-constructed DNA libraries with randomised segments.
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 used for 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 increasingly challenging. 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 life’ and the lack of a specific frame for phage therapy in the current Medicinal Product Regulation. Short-term borderline solutions under the responsibility of a Medical Ethical Committee and/or under the umbrella of the Declaration of Helsinki are emerging. As a long-term solution, however, we suggest the creation of a specific section for phage therapy under the Advanced Therapy Medicinal Product Regulation to papain yields potent peptide inhibitors of
cathepsins L, B, H, and K"
Bacteria-Eating Virus Approved as Food Additive:
Not all viruses harm people. The Food and Drug Administration has approved a mixture of viruses as a food additive to protect people. The additive can be used in processing plants for spraying onto ready-to-eat meat and poultry products to protect consumers from 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 virus that infects bacteria.
Consuming food contaminated with the bacterium L. monocytogenes can cause an infectious disease, listeriosis, which is rarely serious in healthy adults and children, but can be severe and even deadly in pregnant women, newborns, older people, and people with weakened immune systems. Pregnant women are about 20 times more likely than other healthy adults to get listeriosis, according to the Centers for Disease Control and Prevention (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 each year in the
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, may become contaminated within the processing plant after cooking and before packaging. Unlike fresh meat and poultry, the ready-to-eat products can be consumed without reheating, so the L. monocytogenes survive and are ingested.
"L. monocytogenescan continue to thrive even in refrigerated conditions," says Capt. Andrew Zajac, a food safety expert and acting director of the Division of Petition Review within the FDA's Center for Food Safety and Applied Nutrition (CFSAN). "If a food product contaminated with L. monocytogenesis bought by a consumer and brought home and refrigerated, the bacteria can continue to multiply."
How Bacteriophages Work?
Bacteriophages are found in the environment. "We're routinely exposed to bacteriophages," says Zajac. "They are found in soil and water, and they are part of the microbial population in the human gut and oral cavity."
Bacteriophages infect only bacteria, says Zajac. "They don't infect plant or mammalian cells." Thousands of varieties of phages exist, and each one infects only one type or a few types of bacteria. The particular phages approved as a food additive are very specific 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 its host during its life cycle without integrating into the host genome. This type of phage works 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 produce hundreds of new phages and causing the bacterial cell walls to break open. This process kills the bacterium and releases many new phages, which seek out other bacteria to invade and repeat the cycle.
"The process continues until all host bacteria have been destroyed," says Zajac. "Then the bacteriophages cease replicating. They need a host to multiply and will gradually become 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 it is intended and will not cause harmful effects when consumed.
If an additive is approved, the FDA issues a regulation that includes information on the types of foods in which the additive can be used and maximum amounts to be used. The regulation also provides the additive's identity and specifications on purity, which will ensure that the additive used in food is the same substance that was evaluated and approved by the FDA.
Once a food additive is approved, any company can use the additive, says Zajac, as long as it meets the conditions in the regulation.
In response to a petition submitted by industry, the FDA published a regulation in August 2006 permitting the use of a Listeria-specific bacteriophage preparation on ready-to-eat meat 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 can still destroy the bacteria.
The FDA must approve any additive before it can be used in food. When an additive is to be 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 the safety of the ingredient for its intended use. At the same time, the USDA evaluates the ingredient's suitability.
The FDA's food additive regulations define safety as "a reasonable certainty that the substance 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, in part, on published reports submitted by the petitioner on the results of the use of phages in animal and human studies.
The USDA's Food Safety and Inspection Service (FSIS) evaluated the bacteriophage preparation's suitability. "Suitability establishes that the use of a substance is effective in performing 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 and Consumer Protection Staff. In addition, suitability is an assurance that the use of the 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 additive makes 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, both administered by the USDA, the use of the phage preparation must be declared on labeling as an ingredient. Consumers will see "bacteriophage preparation" on the label of meat or poultry products that have been treated with the food additive.If consumers have 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 see what it contains."
A Phage First:
This approval marks the first time that the FDA has regulated the use of a phage preparation as a food additive. Phages are currently approved in the
Scientists continue to be interested in other uses for phages, such as to prevent food products from contamination with other types of harmful bacteria and to act as possible treatments 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 closely resembles the clinical pathophysiology of septicemia in humans. Oral administration of a newly isolated lytic phage strain (KPP10) significantly protected mice against mortality (survival rates, 66.7% for the phage-treated group versus 0% for the saline-treated control group; P<0.01). Mice treated with phage also had lower numbers of viable P. aeruginosa cells in their blood, liver, and spleen. The levels of inflammatory cytokines (tumor necrosis factor alpha TNF-alpha, interleukin-1beta [IL-1beta], and IL-6) in blood and liver were significantly lower in phage-treated mice than in phage-untreated mice. The number of viable P. aeruginosa cells in fecal matter in the gastrointestinal tract was significantly lower in phage-treated mice than in the saline-treated control mice. We also studied the efficacy of phage treatment for intraperitoneal infection caused by P. aeruginosa and found that phage treatment significantly improved the survival of mice, but only under limited experimental conditions. In conclusion, our findings suggest that oral administration of phage may be effective against gut-derived sepsis caused by P. aeruginosa.
Bacteriophages are viruses that only infect bacteria. They have played an important role in the development of molecular biology and have been used as anti-bacterial agents. Since their independent discovery by Twort and d'Herelle, they have been extensively used to prevent and treat bacterial infections, mainly in
Exploiting phages for production of vaccines :
Bacteriophages have a number of potential applications in the biotechnology industry- delivery vehicles for protein and DNA vaccines, for gene therapy, as alternatives to antibiotics, and as protein/antibody library screening tools. This diversity and ease of manipulation and production means they have potential research, therapeutic and manufacturing uses in both the biotechnology and medical fields. It is hoped that the wide range of scientists, clinicians and biotechnologists currently researching or putting bacteriophages to practical use are able to pool their knowledge and expertise and thereby accelerate progress towards further development in this exciting field of biotechnology.
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.
Reference:
1. ^ Hufton SE, Moerkerk PT, Meulemans EV, de Bruïne A, Arends JW, Hoogenboom HR (1999). "Phage display of cDNA repertoires: the pVI display system and its applications for the selection of immunogenic ligands". J. Immunol. Methods 231 (1-2): 39–51. doi:. PMID 10648926, http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T2Y-418YGFH-5&_user=1543454&_coverDate=12%2F10%2F1999&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000053633&_version=1&_urlVersion=0&_userid=1543454&md5=ad85a4991cf0cee17bfec69bc90dd707.
- ^ Gommans WM, Haisma HJ, Rots MG (2005). "Engineering zinc finger protein transcription factors: the therapeutic relevance of switching endogenous gene expression on or off at command". J. Mol. Biol. 354 (3): 507–19. doi:. PMID 16253273, http://www.rug.nl/farmacie/onderzoek/basisEenheden/THErapeuticGeneModulation/publicaties/publicaties2004/2005_6.pdf?as=binary.
- ^ Lunder M, Bratkovic T, Doljak B, Kreft S, Urleb U, Strukelj B, Plazar N. (2005). "Comparison of bacterial and phage display peptide libraries in search of target-binding motif". Appl. Biochem. Biotechnol. 127 (2): 125–31. doi:.
- ^ Bratkovic T, Lunder M, Popovic T, Kreft S, Turk B, Strukelj B, Urleb U. (2005). ^ Lunder M, Bratkovic T, Kreft S, Strukelj B (2005). "Peptide inhibitor of pancreatic lipase selected by phage display using different elution strategies". J. Lipid Res. 2005 46 (7): 1512–6.
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