The following points highlight the six main therapies of bacteriophages. The therapies are: 1. Collection 2. Mode of Action of Phage Preparations 3. Commercial Production of Phages 4. Prophylaxis and Treatment of Bacterial Infections 5. Characteristics of Bacterlophages 6. Bio-Safety.
Therapy # 1. Collection:
Local samples of bacteriophage can be collected from water which possibly contains high quantities of bacteria and bacteriophages, for example effluent outlets, sewage, corpses, etc. The samples are filtered and applied to the bacteria cultured on growth. Usually, the mixture is centrifuged after bacterial death. The phages collect on the top of the mixture are drawn off.
Thereafter, the solutions containing phages are tested to observe which of the bacteriophages show growth suppression effects (lysogeny) and/or lysis of the pathogenic bacteria.
The lytic bacteriophages are the most suitable ones to be used in phage therapy because they completely kill the host cell. The lytic phages are multiplied on cultures of known pathogenic bacteria, passed through a millipore filter to separate phages from bacterial mixture. After purification filtrate is distributed for clinical use.
Therapy # 2. Mode of Action of Phage Preparations:
The success of phage therapy relies on the mechanism or mode of action of bacteriophages. The host bacteria are completely killed by the phages and hundreds of new particles are released after lysing the host bacteria.
Therapy # 3. Commercial Production of Phages:
In Paris, D’Herelle’s commercial laboratory produced at least five phage preparations against various bacterial infections. The preparations were called Bacte-coli-phage, Bacte-rhino-phage, Bacte-intesti-phage, Bacte-pyo-phage, and Bacte-staphy-phage. They were marketed by what later became the large French company L’Oreal . The United States also produced the therapeutic phages.
In the 1940s, the Eli Lilly Company produced seven phage products for human use including preparations against staphylococci, streptococci, E. coli, and other bacterial pathogens.
These preparations consisted of phage-lysed, bacteriologically sterile broth cultures of the targeted bacteria (e.g. Colo-lysate, Ento-lysate, Neiso-lysate, and Staphylo-lysate) or the same preparations in a water- soluble jelly base (e.g. Colo-jel, Ento-jel, and Staphylo-jel). These were used to treat various infections including abscesses, suppurating wounds, vaginitis, acute and chronic infections of the upper respiratory tract and mastoid infections.
In spite of appreciable effect, efficacy of phage preparations was controversial. After the discovery and commercialization of antibiotics, commercial production of therapeutic phages got topped in most of the Western world. Nevertheless, in Eastern Europe and in the former Soviet Union, phages continued to be used herapeutically along with antibiotics or alone.
Several institutions in these countries were actively involved in therapeutic phage research and production at the Eliava Institute of Bacteriophage, Microbiology and Virology (EIBMV) of the Georgian Academy of Sciences, Tbilisi (Georgia), and the Hirszfeld Institute of Immunology and Experimental Therapy (HIIET) of the Polish Academy of Sciences (Poland).
In 1923, Giorgi Eliava (a prominent Georgian Bacteriologist) founded the Eliava Institute. D’Herelle spent several months in Georgia for helping Eliava and other Georgian colleagues. He thought to get settled permanently at Tbilisi. Unfortunately, Eliava was arrested in 1937 by the predecessor of the KGB, pronounced a ‘People’s Enemy’ and executed. D’Herelle became frustrated and never returned to Georgia.
Nonetheless, the EIBMV became one of the largest institutes in the world known for preparation of therapeutic phages. The Institute employed about 1,200 personnel to produce several tones of phage preparations in a day for use against pathogens viz., staphylococci, Pseudomonas, Proteus, and many enteric pathogens.
In 1952, the Hirszfeld Institute was founded which began to produce phages for the treatment of shigellosis, septicemia, furunculosis, and pulmonary and urinary tract infections and for the prophylaxis or treatment of post-operative and post-traumatic infections. In many cases, phages were used against multidmg-resistant bacteria that were refractory to conventional treatment with antibiotics.
Therapy # 4. Prophylaxis and Treatment of Bacterial Infections:
Bacteriophage therapy is used broadly in certain parts of the former Soviet Union, particularly the Republic of Georgia, which has been the global center of phage expertise for over 80 years. The first reviewed report of the therapeutic efficacy of Phago-Bio-Derm (cocktail of lytic bacteriophages) was recently published.
About 107 patients suffering from ulcers failed to response to conventional therapy. Their ulcers healed completely in 70% cases with Phago-Bio-Derm. One of the polyvalent phage preparations produced by the EIBMV is Pioibacteriophagum fluidum. The preparation targets a variety of bacterial pathogens, including P. aeruginosa, E. coli, S. aureus, Streptococcus and Proteus.
Several hundred reports on phage therapy in humans have been published by many countries including Soviet Union, Poland and others. Some of the major human phage therapy studies from Poland and the former Soviet Union are summarized in Table 18.6.
Therapy # 5. Characteristics of Bacterlophages:
Bacteriophages have several characteristics that make them potentially attractive therapeutic agents:
(i) They are highly specific and very effective in lysing targeted pathogenic bacteria,
(ii) They are safe, as underscored by their extensive clinical use in Eastern Europe and the former Soviet Union and the commercial sale of phages in the 1940s in the United States, and
(iii) They are rapidly modifiable to combat the emergence of newly arising bacterial threats.
However, phages may be effective therapeutic agents in selected clinical settings. Many of these studies do not meet the current standards for clinical trials and still there remain many important questions that must be addressed before lytic phages can be widely endorsed for therapeutic use. However, there is need to find alternative treatment against rapidly emerging, antibiotic-resistant bacteria to warrant further studies on phage therapy.
Recently the phage therapy approach has been applied to systemic and intracellular infections. The non-replicating phage and isolated phage enzymes like lysins have also been used. However, definitive proof for the efficiency of these phage approaches in field is limited to only a few cases.
In 1994, 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. Additional support for these findings has been provided by the recent studies.
Yacoby (2006) have proposed the use of phages as delivery mechanisms for traditional antibiotics. The use of phages to deliver antitumor agents has also been described in preliminary in vitro experiments for cells in tissue culture.
Therapy # 6. Bio-Safety:
Phage therapy is generally considered safe. In 2006, Food and Drug Administration (F.D.A.) of the United States approved the spraying meat with phages. Consumers will not know unless labelling of meat and poultry products that it has been treated with the ‘phage spray’ is made mandatory.
The public must be aware about the label, for example phages against Listeria are ‘generally recognized as safe’ (GRAS status) within the scientific community throughout the world.
Now it opens the door for other phages also to be recognized as GRAS. 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, bums, boils, etc.
In the South West Regional Wound Care Center (Texas, U.S.A.), First Phase clinical trials are underway for an approved cocktail of phages against bacteria, including P. aeruginosa, Staphylococcus aureus and E. coll.
After killing bacteria with antibiotic therapy or the other methods endotoxins are released by them within the patient. This causes fever or toxic shock. During manufacturing process one must take care to make phage medium free from bacterial fragments and endotoxins from the production process. Janakiraman Ramachandran, a former president of AstraZeneca India, launched GangaGen Inc. from 2000 ago which is a start up of phage therapy in Bangalore.
He is of the opinion that such complication can be avoided by using genetically engineered bacteriophages. Without this gene which is responsible for producing endolysin the host bacterium dies but remains intact because the lysis is disabled.
This modification stops the exponential growth of phages, so one administered phage means one dead bacterial cell. Eventually the dead cells are consumed by the normal house cleaning phagocytes.
Generally, the lysogenic bacteriophages are not used for therapeutic purpose. Such bacteria can act as a mean for DNA exchange. This can also help in development of antibiotic resistance. It is also possible that it can make the bacteria pathogenic.