Hannah Agnew

Hannah Agnew

Higher Degree by Research Candidate

School of Biological Sciences

Faculty of Sciences


My research investigates the differences between closely related clinical isolates of Streptococcus pneumoniae, which have been taken from different anatomical niches, in hopes of identifying mechanisms that influence the disease tropism.  

Streptococcus pneumoniae is a commensal Gram-positive bacterium that is commonly found in the normal human microflora. However, the pneumococci can switch to cause both local (otitis media) and invasive diseases (meningitis) leading to high rates of morbidity and mortality. One important factor in pneumococcal pathogenesis is the capacity to metabolise different carbohydrates. Different niches of the body vary in their nutrient composition, which requires adaptation by pneumococci to survive, such as the switching between different metabolic pathways. My research aims to examine metabolic differences between closely related paediatric clinical isolates from different anatomical niches. This project will elucidate the molecular mechanisms that contribute to tissue tropism, which may lead to improved vaccines and therapeutic strategies.

Streptococcus pneumoniae is a commensal Gram-positive bacterium that is commonly found in the normal human microflora. However, the pneumococci can switch to cause both local (otitis media) and invasive diseases (meningitis) leading to high rates of morbidity and mortality. 

In the last year, our lab has received clinical isolates of Streptococcus pneumoniae from the German National Reference Center for Streptococci (Aachen) collected in Germany over 17 years, from 2002 to 2019. These isolates were acquired from children, aged 4 months to over 6 years old, admitted to hospital with otitis media, pneumonia, sepsis and meningitis. Specifically, children with otitis media had both ear and nasopharynx isolates collected, whilst children with sepsis or meningitis had both blood and cerebral spinal fluid (CSF) isolates collected. 

These new isolates will be grouped based on clonal lineage before being phenotypically characterised to determine any differences. In particular, the metabolic capabilities of the isolates will be closely examined due to research undertaken previously in the Paton lab that identified genetic differences in metabolic genes within closely related isolates from different niches, which influenced disease tropism. 

My research aims to identify metabolic differences, in vitro and in vivo, between clinical isolates of the same clonal lineage collected from different anatomical niches. Identification of these differences will elucidate the molecular mechanisms that contribute to tissue tropism, which may lead to improved vaccines and therapeutic strategies.


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