Dr. Andy

Reflections on medicine and biology among other things

Wednesday, July 13, 2005

Bacteriophages

Bacteriophages are viruse that infect bacteria. They are now being studied as possible treatment for bacterial infections, particularly those that are resistant to antibiotics.

Apparently these bacterial viruses looked like a promising antimicrobial treatement 100 years ago, but enthusiasm died out with the discovery of penicillin. As we face increasing problems with drug resistance, the idea of phage based therapies is making a comeback, according to an article in the June 25th Lancet.

For whatever reason, phage research continued in Georgia (the country that was formerly part of the Soviet Union, not the US state) and the Eliava Institute in Tbilisi is still at the center of this strategy.

From the article it sounds like the field is still in its infancy. Instead of having pure strains of different bacteriophages for different infections, the researchers at Eliava get mixtures of different phages from sewage (that won’t play well in direct to consumer marketing), which is bad for a number of reasons, not least of which such gamishes will be impossible to get regulatory approval for.

In addition there appears to be a lack of well-controlled trials of bacteriophage therapy

“There are too many evangelists and too little data and it’s still being hyped”, says Ian Molineux, a microbiologist at the University of Texas who specializes in bacteriophages and host–parasite interactions. “There have never really been any proper controlled experiments.” Much of the positive spin on phage therapy is little more than hyperbole, he says.

But biotech companies have become interested, so these weaknesses may soon be remedied.

A final problem is that some bacteriophages (those that are lysogenic and can integrate their DNA into the bacteria’s) have been implicated in spreading genes for antibiotics resistance between different bacterial strains. Any bacteriophages approved for therapy would have to be incapable of this.

Overall I’d view phage therapy as promising and exciting, but unproven.

One important advantage of this approach is that medicine can harness the power of natural selection instead of fighting it. Whenever a new class of antibiotic is approved, a huge number of bacteria in patients treated with it are placed under selective pressure. Any existing resistance is quickly selected for and even if none existed before, random variation can quickly produce it. Genes responsible for this resistance can spread quickly under such powerful selection

With bacteriophages, if bacteria develop resistance to one strain of phage, variant strains which are still effective can be selected in the laboratory. One could even imagine this could be done on an individual patient basis in the (distant) future

1 Comments:

At 11:57 AM, Blogger DrTony said...

Good posts. My thoughts here.

 

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