March 21, 2001 -- While antibiotics still remain the mainstay for treating bacterial infections, researchers may have found a whole new way of treating infections. And this is very good news, as many strains of bacteria have become increasingly resistant to the antibiotics that used to wipe them out.
This new method uses the enzymes of bacteriophages to attack the bacteria. Bacteriophages are tiny viruses that infect bacteria. After they infect the bacteria, they replicate or make copies of themselves, and then leave the bacteria to go and infect other bacteria. To be able to leave the bacteria, the "phages" make an enzyme that dissolves the wall of the bacterial cell, thus killing it.
In a report that appears in this week's issue of the Proceedings of the National Academy of the Sciences, researchers examined the ability of one of these enzymes, called C1 phage lysine, to destroy the bacteria Streptococcus pneumoniae. Streptococcus is responsible for many common and not so common infections, including strep throat, the flesh-eating disease, and rheumatic fever.
Vincent Fischetti, PhD, and his team tested the C1 phage lysin on mice. It was found to be very effective in killing the streptococci organisms, and it killed them very quickly. The researchers found that if they added a small amount of enzyme to a test tube filled with 10 million bacteria, they would all be destroyed within five seconds.
Unlike antibiotics, the enzyme does not seek out the bacteria in all the body's hiding places, but instead just kills the bacteria on contact. The researchers envision that the enzyme could be administered in the form of a spray, to the mucous membranes, for instance, thus eliminating the source of the disease bacteria.
"The enzyme doesn't cure the infection but prevents the spread of it to other people," says Fischetti, who is a professor at Rockefeller University in New York. "It eliminates the organism from an infected individual and prevents it from transmitting to a family member."
So for example, he says, if a child has strep throat and you give the enzyme to the other members of the family, it prevents them from getting strep throat.
Many people are carriers of microorganisms, which means that while they themselves do not get symptoms, they can pass the bacteria to other people. Fischetti, who also is co-head of the Laboratory of Bacterial Pathogenesis at Rockefeller, explains that the enzyme also will eliminate bacteria in carriers as well as those who are actively infected.
Carriers harbor the organism in their mucus membranes, such as the lining of their mouth and nose. "They are spread through contaminated saliva. If you can eliminate that reservoir, you can stop it from spreading."
Louis B. Rice, MD, feels that it is important to emphasize that this enzyme is a potential intervention to stop the growth of the bacteria in the mucus membranes rather than representing a new treatment for streptococcal infection.
"So this enzyme is potentially useful as an agent in outbreak situations, such as day care centers," says Rice, who is an associate professor of medicine at Case Western Reserve University in Cleveland.
"Its use in at-risk subjects could therefore minimize the spread and ultimately reduce the numbers of children and others with clinical infection, " he says. Rice was not involved in the study.
Antibiotics not only destroy destructive bacteria but also the beneficial organisms that our body needs to function. However, the enzyme only attacks specific bacteria, and as a result, may eliminate many of the side effects, such as diarrhea, that are common with antibiotics.
"I can envision giving this to children in a day care center to eliminate the pneumococci they carry in their nose, which would pretty much reduce or eliminate [ear infections] in that population," Fischetti says. "We just can't do that now."
They plan to start human clinical trials in the near future and currently are developing new enzymes that are directed against other types of bacteria.