News 895 views last update:6 Aug 2012

Viruses that attack bacteria

Proteon Pharmaceuticals, a Lódz, Poland-based company that is conducting advanced research to produce a bacteriophage-based preparation to prevent salmonella infections in farm animals, was named the third most innovative biotechnology company in Central and Eastern Europe at this year's BioForum fair in Lódz.

“Bacteriophages were first used as a protective measure against harmful pathogens a century ago, but later the technique was forgotten,” says Jaroslaw Dastych, M.D., owner of Proteon Pharmaceuticals.
“The expertise in making practical use of bacteriophages mainly survived in the former Soviet republic of Georgia and in Poland. Now that bacteria are growing increasingly resistant to antibiotics, this biological method to combat bacteria, abandoned in favour of antibiotics, is back in fashion.”
Proteon Pharmaceuticals was established in 2005 and in October 2009, the company began to deal with bacteriophages, or viruses that attack bacteria.
Bactieriophages are extremely specialized and each strain attacks a different kind of bacteria. Once a phage enters into a bacterial cell, it starts replicating to 30-50 copies, causing the bacterium to disintegrate.
Sometimes the viral genes merge with the bacterial genome, reproducing together with the host, first waiting and then destroying it. When a host is administered a bacteriophage, the virus replicates for only as long as the bacteria of a particular strain remain in the host’s body.
Culture the prey
Bacteriophages are not dangerous to humans, because they never attack human cells. However, in order to multiply a given bacteriophage strain, microbiologists need to culture bacteria that the phage prey on.
If the phage is to be subsequently isolated, the bacteria have to be thoroughly removed. A slight risk occurs that the sample can be contaminated with the bacteria and their toxins.
The phage therapy was originally developed a long time ago, but interest in it resurfaced in the 1990s when after decades of extensive use of antibiotics, many new bacterial strains emerged with a growing resistance to antibiotics.
Researchers in Tbilisi, Georgia, and Wroclaw, Poland, are looking for new phages, because bacteria develop resistance to their viral enemies as well.
The interest in bacteriophages nevertheless continues to grow both in the medical community and beyond.
Bacteriophages vs. salmonella
One of the most serious problems in large-scale production of poultry and eggs is Salmonella. The genus has many subtypes that are difficult to distinguish and birds need some of them to survive—the way humans need the Escherichia coli genus.
Problems begin when the bacteria multiply beyond control, causing trouble at poultry farms and posing a threat to consumers.
The EU has developed a program to eliminate Salmonella-related hazards, involving regular inspection of birds, poultry meat, eggs and chicken coops.
 “When the EU banned the use of antibiotics as feed additives, I thought of culturing bacteriophages against Salmonella,” says Dastych.
“Phages are not antibiotics and they do not stay in the food chain. Consequently, instead of developing a drug to combat a deadly bacterium, I decided we should start from something that worked on chickens.
Three types of phages
“We have been working with a mixture of three phages that we want to put in a feed additive. I believe this method will be much more efficient than, for example, highly acidic feed additives which sterilize chickens’ digestive tracts and result in poor digestion and slow growth of the birds.
“We could pick a specific phage strain to attack only certain types of Salmonella. We are aiming for a standardized preparation at the molecular level and have been examining DNA sequences and analyzing the genomes of each bacteriophage to check if it has been classified before.
“Most of them have not, because there are lots of different bacteriophages. I believe the study and use of bacteriophages marks a new trend in biotechnology and we will live to see other applications of the method, some of them more successful than others.”

Dick Ziggers

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