# Role and regulation of a peptidoglycan synthesis enzyme required for cephalosporin resistance in enterococci

> **NIH NIH F31** · MEDICAL COLLEGE OF WISCONSIN · 2022 · $46,752

## Abstract

PROJECT SUMMARY/ABSTRACT:
Infective endocarditis, a condition in which bacteria grow in a biofilm-like state on the valves of the heart, is a
deadly complication of bloodstream infections. Enterococcus species are responsible for 30% of healthcare-
acquired endocarditis. When caused by multi-drug resistant strains, such as vancomycin-resistant enterococci
(VRE), infective endocarditis is nearly untreatable and uniformly fatal. The CDC considers VRE a serious threat
and estimates 5,400 VRE-related deaths and over $500 million in associated healthcare costs in 2017. A major
risk factor for the development of enterococcal endocarditis and other infections is prior treatment with
cephalosporin antibiotics. The two most clinically relevant species of Enterococcus, E. faecalis and E. faecium,
are intrinsically resistant to cephalosporins. Treatment with cephalosporin antibiotics allows commensal
enterococci to proliferate and disseminate to the bloodstream, a prerequisite for infection of the heart valves.
The goal of this project is to further our understanding of molecular mechanisms of cephalosporin resistance in
enterococci. This understanding will enable development of new therapies that both reduce the occurrence of
enterococcal infections and improve treatment options to overcome recalcitrant endocardial infections.
Specifically, a novel link will be investigated between two known cephalosporin resistance determinants, IreK
and MurAA. IreK is a kinase that is thought to sense and respond to cell wall stress, including that caused by
inhibition of peptidoglycan crosslinking upon cephalosporin treatment. However, the targets of IreK signaling that
facilitate this response, and ultimately cephalosporin resistance, are largely unknown. MurAA, an enzyme that
catalyzes the first committed step in peptidoglycan synthesis is also required for cephalosporin resistance. The
central hypothesis of this project is that MurAA is a downstream target of IreK signaling, such that regulation of
MurAA is one mechanism by which IreK controls cephalosporin resistance. Preliminary evidence suggests that
this regulation is mediated by the known IreK-phosphorylation substrate, IreB. This hypothesis will be addressed
in two aims. Aim 1 will determine how IreB and IreK signaling impact functions of MurAA. Aim 2 will identify
MurAA interaction partners and determine the functional consequences of these interactions. Preliminary data
suggest that a protein-protein interaction is important for either facilitating or regulating functions of MurAA.
This work will be conducted at the Medical College of WI under the sponsorship of Dr. Christopher Kristich. The
sponsor and institution are well-equipped to provide resources and support for this fellowship. In collaboration
with the sponsor, the candidate has designed a training plan that complements this project. The training plan
supports development of broad technical, communication and mentoring skills and encourages the profe...

## Key facts

- **NIH application ID:** 10324562
- **Project number:** 5F31AI156980-02
- **Recipient organization:** MEDICAL COLLEGE OF WISCONSIN
- **Principal Investigator:** Carly Mascari
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $46,752
- **Award type:** 5
- **Project period:** 2021-01-01 → 2022-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10324562

## Citation

> US National Institutes of Health, RePORTER application 10324562, Role and regulation of a peptidoglycan synthesis enzyme required for cephalosporin resistance in enterococci (5F31AI156980-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10324562. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*