Faculty Collaboration Database

CroR Regulates Expression of pbp4(5) to Promote Cephalosporin Resistance in Enterococcus faecalis. mBio 2022 Aug 30;13(4):e0111922

Date

08/02/2022

Pubmed ID

35913163

Pubmed Central ID

PMC9426447

DOI

10.1128/mbio.01119-22

Scopus ID

2-s2.0-85137010276 (requires institutional sign-in at Scopus site)   6 Citations

Abstract

Enterococcus faecalis is an opportunistic pathogen and a major cause of severe nosocomial infections. Treatment options against enterococcal infections are declining due to the resistance of enterococci to numerous antibiotics. A key risk factor for developing enterococcal infections is treatment with cephalosporin antibiotics, to which enterococci are intrinsically resistant. For susceptible organisms, cephalosporins inhibit bacterial growth by acylating the active site of penicillin-binding proteins (PBPs), key enzymes that catalyze peptidoglycan cross-linking. Two specific PBPs of enterococci, Pbp4(5) and PbpA(2b), exhibit low reactivity toward cephalosporins, allowing these PBPs to cross-link peptidoglycan in the presence of cephalosporins to drive resistance in enterococci, but the mechanisms by which these PBPs are regulated are poorly understood. The CroS/R two-component signal transduction system (TCS) is also required for cephalosporin resistance. Activation of CroS/R by cephalosporins leads to CroR-dependent changes in gene expression. However, the specific genes regulated by CroS/R that are responsible for cephalosporin resistance remain largely unknown. In this study, we characterized CroR-dependent transcriptome remodeling by RNA-seq, identifying pbp4(5) as a CroR regulon member in multiple, diverse lineages of E. faecalis. Through genetic analysis of the pbp4(5) and croR promoters, we uncovered a CroR-dependent regulatory motif. Mutations in this motif to disrupt CroR-dependent upregulation of pbp4(5) in the presence of cell wall stress resulted in a reduction of resistance to cephalosporins in E. faecalis, demonstrating that enhanced production of Pbp4(5) and likely other proteins involved in peptidoglycan biogenesis by the CroS/R system drives enterococcal cephalosporin resistance. IMPORTANCE Investigation into molecular mechanisms used by enterococci to subvert cephalosporin antibiotics is imperative for preventing and treating life-threatening infections. In this study, we used genetic means to investigate the functional output of the CroS/R TCS required for enterococcal resistance to cephalosporins. We found that enhanced production of the penicillin-binding protein Pbp4(5) upon exposure to cell wall stress was mediated by CroS/R and was critical for intrinsic cephalosporin resistance of E. faecalis.

Author List

Timmler SB, Kellogg SL, Atkinson SN, Little JL, Djorić D, Kristich CJ

Authors

Samantha N. Atkinson PhD Bioinformatics Analyst III in the Microbiology and Immunology department at Medical College of Wisconsin
Dusanka Djoric Research Scientist I in the Microbiology and Immunology department at Medical College of Wisconsin
Christopher J. Kristich PhD Professor in the Microbiology and Immunology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Anti-Bacterial Agents
Bacterial Proteins
Cephalosporin Resistance
Cephalosporins
Enterococcus faecalis
Microbial Sensitivity Tests
Penicillin-Binding Proteins
Peptidoglycan