Greetings SITN members!
Well, we are rapidly approaching the conclusion of our 2006 seminar series. Please join us this Thursday, November 16th, from 7-9pm, for our final seminar of the season: Global Warming: Is it Getting Hot in Here? This seminar will also be presented Nov 20th at the Mildred Ave. Community Center in Mattapan.
Many thanks to those of you who have participated in the seminar series this season, especially for giving us your attention, your questions, and your feedback on our survey so that we can make next year’s series even better. As a reminder, if your questions were not answered at a seminar or you have other questions related to science and medicine, please check out the question and answer forum on our webpage (http://sitn.hms.harvard.edu/) and we will do our best to get you some answers.
--The SITN Staff
Would You Like Some Bacteriophage With Your Sandwich?
On August 18, 2006, the Food and Drug Administration (FDA) announced its approval of a bacteriophage spray to be used on ready-to-eat meat and poultry products in order to prevent listeriosis, the most deadly food-borne illness in the country. According to the Centers for Disease Control and Prevention (CDC), each year 2,500 people in the United States become sick from listeriosis, which is caused by the bacteria Listeria monocytogenes, and about 500 die from the infection. Those usually affected are pregnant women, newborns, and adults with weakened immune systems. The FDA’s approval of this bacteriophage spray marks the first time in its history that it has approved a bacteriophage preparation to be used on food.
The spray, which was developed by Intralytix, Inc., a biotechnology company based in Baltimore, MD, contains a mixture of six different types of bacteriophage, or “bacteria-eating” viruses, and it may be coming to a grocery store near you. But the use of this bacteriophage spray has some people concerned. What exactly is a bacteriophage? Is it safe? Is there reason to be concerned about consuming food that have been treated with bacteriophage? .
Bad for Bacteria; Good for us?
Most people don’t realize that bacteriophage are everywhere: in our water, in the soil, and even in our bodies including in our intestines and mucous membranes. Bacteriophage experts say that these tiny viruses are the most abundant life form on Earth. So small are bacteriophage, that millions of them could fit on the head of a pin, and Vincent Fischetti, a microbiology professor at Rockefeller University in New York, estimates that “about 10 million [bacteriophage] commonly reside in a single [drop] of unpolluted water”. Bacteriophage are safe to humans -- they cannot infect plant or animal cells, only bacteria. And they are great at what they do. For every bacterium there is an army of bacteriophage that find it, infect it, hijack it for their own replication, and eventually destroy it, releasing hundreds of new bacteriophage to continue the process until the local bacteria population is eliminated.
Bacteriophage were first identified about a century ago, and scientists were excited at the prospect of using bacteriophage to control bacterial diseases. However, mixed results due to haphazard treatment of infections with the wrong bacteriophages, combined with the discovery of antibiotics, led to a decline in bacteriophage research. But while Western physicians largely abandoned bacteriophage research, scientists in the former Soviet Union continued the research, performing many clinical studies and forming institutes devoted to bacteriophage therapy. Even today, some cities in Eastern European countries have stockpiles of bacteriophage available to patients when antibiotics fail to work on their infections.
What’s This In My Bologna?
Bacteriophage are extremely specific- not only do they only infect bacteria, they only infect certain kinds of bacteria. This predator-prey relationship between a bacteriophage and its target bacteria has been around since the beginning of life on Earth. Some bacteria have evolved to resist bacteriophage infection, but bacteriophages have evolved as well to counteract the defenses. The rationale for Intralytix’s formulation of six different bacteriophages in their spray is to minimize the possibility that Listeria will develop resistance to the formulation, as well as to provide overlapping coverage, because no single bacteriophage strain is able to kill all strains of Listeria.
The bacteriophage spray will be used in meat and poultry processing plants on ready-to-eat meat and poultry products such as cold cuts and hotdogs. These foods can become contaminated with Listeria during production, and unlike other bacteria, Listeria can multiply at low temperatures, so refrigerating meats does not prevent the bacteria’s growth. The advantage of the bacteriophage spray is that any Listeria growing on food products should be destroyed long before anyone opens the package. According to the United States Department of Agriculture, the use of the bacteriophage spray will need to be declared on the label of the treated product.
A major hurdle that proponents of this bacteriophage spray will need to overcome is that of public perception. Fischetti sums up the sentiment of the wary consumer: "It's just scary because everybody says stay away from viruses, and now we are eating them." It is unclear which companies will utilize the bacteriophage treatment on their products, but it seems as though consumers could determine how mainstream and accepted this practice will become. John Vazzana, president and chief executive of Intralytix says the company plans to seek approval in the next year for additional bacteriophage products that would be effective against E. coli and salmonella which are other common bacterial contaminants of meats, eggs and produce.
More Uses for Bacteriophage?
Other bacteriophage products currently in development pay homage to the initial, therapeutic role of bacteriophage, that is, as antibiotics. Antibiotic resistance is a growing problem in this country (see February’s edition of the SITNewsFlash). According to the CDC, there has been a steady rise in the number of cases of bacterial infections resistant to antibiotics. Several biotechnology companies are re-embracing bacteriophage therapy as a potential solution to antibiotic drug resistance. While information gathered from the Soviet Union studies is valuable to researchers, the U.S. and Western European regulatory agencies have notoriously tough regulations for human therapies, especially ones for which there is no precedent. Thus, in order to approve bacteriophage therapies for infectious diseases in the United States, biotech companies and the FDA need to wade through these uncharted waters together.
The FDA’s approval of a bacteriophage spray as a food additive may have opened the door in this country for the development of bacteriophage-based therapies to treat infectious diseases. In the near future, we may be utilizing the activity of bacteriophage to prevent and treat a wide range of bacterial illnesses. The bacteriophage, meanwhile, will just continue to do what it does best — “eating” bacteria.
-- Denise Chun, Harvard Medical School
For More Information:
An FDA Questions and Answers site regarding the bacteriophage preparation: <www.cfsan.fda.gov/~dms/opabacqa.html>
An LA Times reporter describes the FDA's approval of the bacteriophage as a food additive: <http://www.sunherald.com/mld/sunherald/living/15403521.htm>
A good article discussing the history of bacteriophage therapy: Stone, R. Bacteriophage Therapy: Stalin's Forgotten Cure. Science. Oct 25, 2002 . 298(5594):728-731.
A short review of current research on phage therapy and potential future applications: Thiel, K. Old Dogma, New Tricks-21 st Century Phage Therapy. Nature Biotechnology. Jan 2004. 22(1): 31-36.
