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Microbiology Logo Microbiology & Immunology
Te Tari Moromoroiti me te Ārai Mate

Dr Rachel Darnell

Research interests:

Clinical and molecular microbiology; Antimicrobial resistance; Antimicrobial tolerance; Enterococci

Current research:

Understanding mechanisms of antimicrobial tolerance in the bacterial pathogen Enterococcus faecalis

Enterococci are intrinsically tolerant to a number of antimicrobials including vancomycin and the recently discovered antimicrobial teixobactin. We have previously identified the two-component regulatory system CroRS as essential for antimicrobial tolerance in Enterococcus faecalis. What we are now interested in understanding is what genes CroRS regulates to confer this tolerance and the molecular mechanisms of this tolerance. In addition, we are developing a pipeline to carry out genome-wide association analyses of enterococcal genomes to identify novel factors of antimicrobial tolerance. 


Targeting antimicrobial tolerance in the bacterial pathogen Enterococcus faecalis

Antimicrobial tolerance is known to precede the development of antimicrobial resistance. In addition, antimicrobial tolerance increases the risk of treatment failure, particularly in the immunocompromised. Our aim is to identify inhibitors of antimicrobial tolerance that will work synergistically with current antimicrobials to reduce the development and spread of antimicrobial resistance. 


Determining the role of Type I phase-variable restriction modification systems in enterococci

We have identified a number of Type I phase-variable restriction modification systems in enterococci. Now we are investigating the role and regulation of these phase-variable systems in both Enterococcus faecalis and Enterococcus faecium.


Enterococcus Group 2022

Enterococcus Group 2022


Current Students:

PhD students

Olivia Paxie (2022 - present)


MSc students

Matigan Smith (2022 - present)


Honours students

Caitlin Cleary, 2023


Past students:

Francesca Todd Rose, PhD Microbiology, 2019 - 2022

Georgia Campbell, MSc Microbiology, 2021 - 2022 

Phoebe Shaw, BSc (Hons) Microbiology, 2022

Sam Gastrell, BSc (Hons) Microbiology, 2022

Olivia Paxie, BSc (Hons) Microbiology, 2021

Georgia Campbell, BSc (Hons) Microbiology, 2020

Hannah Hodgkinson, BSc(Hons) Genetics, 2020

Isobella Campbell, B BiomedSci (Hons), 2018

Francesca Todd Rose, B BiomedSci (Hons), 2018


Darnell, R. L., Paxie, O., Todd Rose, F. O., Morris, S., Krause, A. L., Monk, I. R., Smith, M. J. B., Stinear, T. P., Cook, G. M., Gebhard, S. (2022) Antimicrobial tolerance and its role in the development of resistance: Lessons from enterococci. Advances in Microbial Physiology, 81, 25-65.

Darnell, R. L., Nakatani, Y., Knottenbelt, M. K., Gebhard, S., & Cook, G. M. (2019). Functional characterization of BcrR: A one-component transmembrane signal transduction system for bacitracin resistance. Microbiology, 165, 475-487.  doi: 10.1099/mic.0.000781

Rushton-Green, R., Darnell, R. L., Taiaroa, G., Carter, G. P., Cook, G. M., & Morgan, X. C. (2019). Agricultural origins of a highly persistent lineage of vancomycin-resistant Enterococcus faecalis in New Zealand. Applied & Environmental Microbiology85(13), e00137-19.  doi: 10.1128/aem.00137-19

Darnell, R. L., Knottenbelt, M. K., Todd Rose, F. O., Monk, I. R., Stinear, T. P., & Cook, G. M. (2019). Genomewide profiling of the Enterococcus faecalis transcriptional response to teixobactin reveals CroRS as an essential regulator of antimicrobial tolerance. mSphere4(3), e00228-19.  doi: 10.1128/mSphere.00228-19

Holman, S. K., Daniel, P., Jenkins, Z. A., Herron, R. L., Morgan, T., Savarirayan, R., … Robertson, S. P. (2011). The male phenotype in osteopathia striata congenita with cranial sclerosis. American Journal of Medical Genetics Part A155(10), 2397-2408.  doi: 10.1002/ajmg.a.34178