A cystic fibrosis infection monitor

Student thesis: Doctoral Thesis


P. aeruginosa causes chronic infections in people with the inherited disorder, cystic fibrosis (CF). These chronic infections result in a high rate of morbidity and mortality. Once established, the infections are almost impossible to eradicate. Pulmonary exacerbations, thought to be caused by P. aeruginosa, result in further damage that leads to deterioration in lung performance. A sensor that would allow rapid, near patient testing of sputum samples would be a valuable addition to CF care by enabling more proactive identification of lung infections. In this study, a sensor has been developed using low cost screen printing in conjunction with electrochemical impedance spectroscopy for the detection of P. aeruginosa. Screen printed electrodes were developed and characterised. An impedance normalisation approach, developed in previous work, was used to identify characteristic changes in the impedance signature during the growth of P. aeruginosa. Changes in the normalised impedance were observed under aerobic conditions in standard laboratory media and also under conditions more representative of the CF airway. Specifically, testing was carried out in a number of different scenarios, culminating in tests in an artificial sputum medium that show Pseudomonas aeruginosa can be detected in the presence of Staphylococcus aureus, Haemophilus influenzae or Candida albicans. Investigations using mutant strains of P. aeruginosa PA14 demonstrate that the changes in impedance are largely related to the production of redox active phenazine compounds, including pyocyanin. Slight changes in the impedance were observed with S. aureus and H. influenzae, but were not the same as those observed with P. aeruginosa. This suggests that the sensor could be clinically useful for the detection of P. aeruginosa in patients with CF. After gaining the appropriate ethics approval, a pilot study was also carried out in human sputum samples from CF patients. This study involved further development of the electrode and anecdotally suggests that the presence of P. aeruginosa could be detectable in sputum from patients. Future development should focus upon the optimisation of the device through effective integration into a sample pot which could include an increase in the number of electrodes used per sample, adjustment of the potential for more sensitive detection of pyocyanin and improvements in the consistency achieved between sensors.
Date of Award13 Oct 2015
Original languageEnglish
Awarding Institution
  • University Of Strathclyde

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