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Antibiotic ‘Smart Bomb’ Targets Specific Strains of Bacteria

Findings set stage for next-generation antibiotics, authors say (January 31)

Researchers at North Carolina State University have developed a de facto antibiotic “smart bomb” that can identify specific strains of bacteria and sever their DNA, eliminating the infection. The technique offers a potential approach to treating infections by multidrug-resistant bacteria.

The new findings were published online in mBio.

“Conventional antibiotic treatments kill both ‘good’ and ‘bad’ bacteria, leading to unintended consequences, such as opportunistic infections,” said lead author Chase Beisel, PhD. “What we’ve shown in this new work is that it is possible to selectively remove specific strains of bacteria without affecting populations of good bacteria.”

The new approach works by taking advantage of part of an immune system present in many bacteria called the CRISPR-Cas system. This system protects bacteria from invaders, such as viruses, by creating small strands of CRISPR RNAs, which match DNA sequences specific to a given invader. When the CRISPR RNAs find a match, they unleash Cas proteins, which cut the DNA.

The researchers demonstrated that designing CRISPR RNAs to target DNA sequences in the bacteria themselves causes bacterial “suicide,” as a bacterium’s CRISPR-Cas system attacks its own DNA.

The researchers tested the approach in controlled cultures with different combinations of bacteria present, and were able to eliminate only the targeted strain. They were also able to demonstrate the precision of the technique by eliminating one strain of a species, but not another strain of the same species, which shares 99% of the same DNA.

The researchers are working to develop methods for delivering CRISPR RNAs in clinical settings. “This sets the stage for next-generation antibiotics using programmable CRISPR-Cas systems,” said co-author Rodolphe Barrangou, PhD.

Source: North Carolina State University; January 31, 2014.

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