Antibiotic smart bomb that only kills 'bad' bacteria

Here comes an antibiotic 'smart bomb' that can select specific strains of bacteria, damage their DNA and eliminate the infection.

"Conventional antibiotic treatments kill both 'good' and 'bad' bacteria, leading to unintended consequences such as opportunistic infections," said Chase Beisel, an assistant professor of chemical and biomolecular engineering at North Carolina State University in the US.

The approach shows it is possible to selectively remove specific strains of bacteria without affecting populations of good bacteria, added Beisel.

The technique offers a potential approach to treat infections by multi-drug resistant bacteria.

The new approach works by taking advantage of a part of an immune system present in many bacteria called the CRISPR-Cas system.

The CRISPR-Cas system protects bacteria from invaders such as viruses by creating small strands of RNA called CRISPR RNAs, which match DNA sequences specific to a given invader.

When those CRISPR RNAs find a match, they unleash Cas proteins that 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.

"In lab testing, we found that this approach removes the targeted bacteria. We're encouraged by the ease in specifically targeting different bacteria and the potency of elimination," said Beisel.

"For example, we were able to eliminate Salmonella (a common cause of food-borne illness) in a culture without affecting good bacteria normally found in the digestive tract," he added.

This sets the stage for next-generation antibiotics, said Rodolphe Barrangou, associate professor at NC State.