Shanika Crusz

Current Research

Exploring the molecular mechanisms of bacterial pathogenesis set within the wider context of bacterial social behaviour. Unraveling the complexities of these sophisticated interactions may underpin the development of novel anti-infective strategies particularly aimed at mixed and chronic bacterial infections.

Collaborative projects include 1. The exploration of the ecology of the cystic fibrosis lung and implications for clinical practice, with particular reference to antimicrobial sensitivity testing and treatment strategies. 2. The development of bacterial cheat technology as a novel anti-infective strategy. 3. Whether QS and strain type of P. aeruginosa influence clinical status in patients with cystic fibrosis. 4. Optimisation of the flow chamber biofilm system.

Past Research

The aim of my Ph.D research was to elucidate some of the molecular mechanisms governing the pathogenesis of P. aeruginosa in the cystic fibrosis lung, with particular reference to quorum sensing (QS), a cell-to-cell communication system involving the production and sensing of diffusible signal molecules. This included the investigation of the role of the QS-regulated lectins LecA and LecB in biofilm formation. The potential of P. aeruginosa N-acylhomoserine lactone and 2-alkyl-4-quinolone QS signal molecules as diagnostic markers for predicting the effectiveness of IV antibiotic therapy in controlling pulmonary exacerbations caused by P. aeruginosa was also explored.

Main outcomes: 1 The establishment of a clinical study, with the recruitment of adult and paediatric patients with cystic fibrosis. Serial sputum samples were collected and a cohort of clinical P. aeruginosa strains isolated and characterised with respect to their QS phenotype. 2 Using both biosensors and liquid chromatography-mass spectroscopy (LC-MS), clinical isolates were found to synthesise a range of QS signal molecules. In addition, lecA, a QS regulated gene was conserved and expressed by these isolates. 3 QS signal molecules were detected in sputum samples and some associations between sputum QS signal molecule levels and cystic fibrosis disease status, response to IV antibiotics and the presence of non-cultured P. aeruginosa were established. 4 A flowchamber biofilm system and the associated COMSTAT and IMARIS technology was set up and optimised. 5 LecA was demonstrated to contribute to biofilm maturation in both laboratory and clinical strains and hydrophobic galactosides shown to be able to inhibit biofilm development. The putative biofilm target ligand for LecA was tentatively identified as the Psl exopolysaccharide. 6 Mutants defective in either lecA or lecB or both were constructed and shown to produce defective biofilms which could be inhibited and/or dispersed by galactosides or furanosides respectively, including novel synthetic furanoside dendrimers. The latter proved inhibitory to both laboratory and clinical P. aeruginosa isolates and constitute a potential novel therapeutic.