AUTHOR=Mortensen Kate , Lam Tony J. , Ye Yuzhen TITLE=Comparison of CRISPR–Cas Immune Systems in Healthcare-Related Pathogens JOURNAL=Frontiers in Microbiology VOLUME=Volume 12 - 2021 YEAR=2021 URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.758782 DOI=10.3389/fmicb.2021.758782 ISSN=1664-302X ABSTRACT=The ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) and Clostridium difficile have been identified as the leading global cause of multidrug-resistant bacterial infections in hospitals. CRISPR-Cas systems are bacterial immune systems, empowering the bacteria with defense against invasive mobile genetic elements that may carry the antimicrobial resistance (AMR) genes , among others. On the other hand, the CRISPR-Cas systems are themselves mobile. In this study, we annotated and compared the CRISPR-Cas systems in these pathogens, utilizing their publicly available large numbers of sequenced genomes (e.g., there are more than 12 thousands of S. aureus genomes). The presence of CRISPR-Cas systems showed a very broad spectrum in these pathogens: S. aureus has the least tendency of obtaining the CRISPR-Cas systems with only 0.55% of its isolates containing CRISPR-Cas systems, whereas isolates of C. difficile we analyzed have CRISPR-Cas systems each having multiple CRISPRs. Statistical tests show that CRISPR-Cas containing isolates tend to have more AMRs for four of the pathogens (A. baumannii, E. faecium, P. aeruginosa, and S. aureus). We made available all the annotated CRISPR-Cas systems in these pathogens with visualization at a website (https://omics.informatics.indiana.edu/CRISPRone/pathogen), which we believe will be an important resource for studying the pathogens and their arms-race with invaders mediated through the CRISPR-Cas systems, and for developing potential clinical applications of the CRISPR-Cas systems for battles against the antibiotic resistant pathogens.