Enterococcus faecalis and E. faecium are normal human intestinal tract colonizers and opportunistic pathogens that are among the leading causes of hospital-acquired infections in the US. Specific phylogenetic lineages of E. faecalis and E. faecium cause hospital-acquired infections. These hospital enterococci are multidrug-resistant and possess dramatically expanded genomes relative to commensal enterococcal strains. Genome expansion is due to the acquisition of mobile genetic elements (MGEs) such as plasmids and phage. Interestingly, hospital enterococci lack CRISPR-Cas systems. CRISPR-Cas are prokaryotic genome defense systems that serve as molecular memories of past MGE encounters and that provide acquired immunity against MGEs. These results suggest that antibiotic treatment inadvertently selects for enterococci with enhanced abilities to acquire MGEs. The central hypothesis guiding this research is that compromised genome defense combined with strong selection for MGEs leads to the emergence of multidrug-resistant, genome- expanded enterococci endemic to clinical environments. In preliminary work supported by a NIAID K22 Research Scholar Development Award, we demonstrated that a CRISPR-Cas system in commensal E. faecalis acts as an impediment to the acquisition of antibiotic resistance. The research in this proposal investigates the function of a unique orphan CRISPR locus occurring in hospital E. faecalis strains, called CRISPR2, which regulates the antimicrobial stress response of those strains (Aim 1). We have observed that acquisition of an antibiotic resistance plasmid by commensal E. faecalis leads to molecular memory loss (CRISPR deletion) in plasmid-containing cells over time. Mechanisms by which the plasmid evades host CRISPR-Cas defense and induces molecular memory loss will be investigated (Aim 2). Finally, we investigate the hypothesis that hospital enterococci are dysfunctional for `self' versus non-self recognition; i.e. genome modification defense (Aim 3).

Public Health Relevance

Enterococci are among the leading causes of hospital-acquired infections in the United States. Increasing antibiotic resistance is characteristic of these bacteria. The research proposed here investigates the relationship of bacterial self-defense systems, called CRISPR-Cas and restriction-modification, to the emergence of antibiotic resistance in enterococci.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
1R01AI116610-01A1
Application #
8981386
Study Section
Genetic Variation and Evolution Study Section (GVE)
Program Officer
Huntley, Clayton C
Project Start
2015-04-15
Project End
2020-03-31
Budget Start
2015-04-15
Budget End
2016-03-31
Support Year
1
Fiscal Year
2015
Total Cost
$382,500
Indirect Cost
$132,500
Name
University of Texas-Dallas
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
800188161
City
Richardson
State
TX
Country
United States
Zip Code
75080
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Duerkop, Breck A; Huo, Wenwen; Bhardwaj, Pooja et al. (2016) Molecular Basis for Lytic Bacteriophage Resistance in Enterococci. MBio 7:
Price, Valerie J; Huo, Wenwen; Sharifi, Ardalan et al. (2016) CRISPR-Cas and Restriction-Modification Act Additively against Conjugative Antibiotic Resistance Plasmid Transfer in Enterococcus faecalis. mSphere 1: