Enterococcus faecalis

 

Enterococcus faecalis is a gram-positive bacterium commonly found as a commensal organism in the gastrointestinal tract of most mammals. However, E. faecalis frequently exhibits resistance to available antibiotics and is one of the leading causes in many hospital acquired infections including endocarditis, urinary tract infections and intra-abdominal infections. The emergence of antibiotic resistance to conventional antibiotics such as vancomycin is fast becoming increasingly difficult for clinicians to treat with currently available therapeutic agents.

There is a need to identify new metabolic targets that are essential for bacterial survival and proliferation within its host  in order to strategically develop new and efficient drugs against enterococci and other pathogenic bacteria,. To achieve this, an intimate understanding is required of how pathogenic bacteria survive and grow under the environmental conditions of its host.

A key strategy utilised by our lab is to identify novel drug targets involves an in silico genome scale metabolic network reconstruction of E. faecalis based in its genome sequence information. This model will allow us to explore the survival mechanisms of E. faecalis under stress conditions.

Metabolic model reconstructions consist of gathering all available information on the target organism and organising that information in a standard format such as ‘xls’. Subsequently, this information can later be edited and manually curated using information available in the literature and online databases. Once the model is curated, the information can be exported to a standard markup language used in model reconstruction, known as SBML (Systems Biology Markup Language). Utilising a variety of different softwares (OptFlux, Matlab), the model can predict and simulate the phenotypic behaviour of the target organism with accuracy, enabling us to unravel metabolic pathways essential for E. faecalis survival under stressing conditions.

One of our main objectives is to explore the metabolic response of E. faecalis to oxidative stress. Reactive oxygen and nitrogen species play significant roles in immune defence and has also been implicated in contributing to the bactericidal activities of antibiotics. Thus, the virulence of E. faecalis has profound dependence on its ability to tolerate oxidative stress. Thus, we are examining how the bacterium tolerates oxygen and sub-lethal concentrations of hydrogen peroxide by constructing metabolite and metabolic flux profiles. These are complemented by gene knock-out mutagenesis of selected pathways with potential role on oxidative stress tolerance.

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The University of Auckland