CRISPR-Cas-Based Antimicrobials: Design, Challenges, and Bacterial Mechanisms of Resistance

The emergence of antibiotic-resistant bacterial strainsis a sourceof public health concern across the globe. As the discovery of newconventional antibiotics has stalled significantly over the past decade,there is an urgency to develop novel approaches to address drug resistancein infectious diseases. The use of a CRISPR-Cas-based system for theprecise elimination of targeted bacterial populations holds promiseas an innovative approach for new antimicrobial agent design. TheCRISPR-Cas targeting system is celebrated for its high versatilityand specificity, offering an excellent opportunity to fight antibioticresistance in pathogens by selectively inactivating genes involvedin antibiotic resistance, biofilm formation, pathogenicity, virulence,or bacterial viability. The CRISPR-Cas strategy can enact antimicrobialeffects by two approaches: inactivation of chromosomal genes or curingof plasmids encoding antibiotic resistance. In this Review, we providean overview of the main CRISPR-Cas systems utilized for the creationof these antimicrobials, as well as highlighting promising studiesin the field. We also offer a detailed discussion about the most commonlyused mechanisms for CRISPR-Cas delivery: bacteriophages, nanoparticles,and conjugative plasmids. Lastly, we address possible mechanisms ofinterference that should be considered during the intelligent designof these novel approaches.