(333e) Selective Killing of Bacteria With the Crispr Immune System

One of the greatest challenges facing modern medicine is the rise and spread of multidrug resistance. Most research efforts have focused on developing novel classes of antibiotics to supplement our current arsenal. However, these same antibiotics will be subject to the same mechanisms of resistance, providing at best a temporary solution to this growing epidemic. A promising alternative is the development of novel treatment strategies that circumvent common mechanisms of resistance. Here, we describe such a strategy that, unlike existing antibiotics, can differentiate between pathogens and the multitude of beneficial bacteria within our bodies. Our strategy relies on “tricking” the CRISPR immune system into recognizing the genome as a foreign invader, inducing genome destruction and bacterial cell death. Recognition is conducted by CRISPR RNAs that can be designed to target almost any genomic sequence. Using existing databases of genomic sequences, CRISPR RNA sequences can be rationally designed that differentiate between harmful and beneficial bacteria. Using the Type I-E CRISPR system in Escherichia coli as a model, we observed potent and selective killing of E. coli and Salmonella typhimurium. We further found that CRISPR RNAs could be designed to readily differentiate between even between closely related strains. These findings offer alternative strategies in the ongoing fight against multidrug resistance. Furthermore, our findings may lead to novel tools in systems biology for the analysis of complex microbial consortia, the evolution of interactions between bacteria and bacteriophages, and the system-wide response to double-stranded DNA breaks.