Researchers from Boston University and Massachusetts Institute of Technology have genetically modified viruses that defeat bacterial defense systems, which could enhance the effectiveness of antibiotics. This new approach could also kill bacteria that have already developed antibiotic resistance. The results of the study were published in the March 2, 2009 online issue of the Proceedings of the National Academy of Sciences (PNAS).
According to the Centers for Disease Control and Prevention (CDC), bacteria that have developed resistance to antibiotics pose a serious health risk. In fact, the antibiotic-resistant bacterium, methicillin-resistant Staphylococcus aureus (MRSA), causes about 94,000 infections and 19,000 every year in the United States.
The modified viruses target the SOS system (a bacterial DNA repair structure enlisted when bacteria make contacts with antibiotics that damage the DNA) and some other gene networks. When used in combination with traditional antibiotics, the engineered viruses weaken the bacterial defense system and prevent antibiotic resistance from developing.
The scientists tested their phages using three classes of antibiotics -aminoglyclosides, beta-lactams, and quinolones – and yielded good outcomes with all three. Mice infected with bacteria were treated. Those mice treated with both antibiotics and modified bacteriophage had an 80% survival rate, while only 50% of the mice survived when treated with antibiotics and natural bacteriophages, 20% for mice treated with antibiotics, and 10% for untreated mice.
"This work lays the groundwork for the development of a library of bacteriophages, each designed to attack different bacterial targets," said Timothy Lu, lead author of the paper and an MD candidate in the Harvard-MIT Division of Health Sciences and Technology.