Abstract
Electrochemical Impedance Spectroscopy (EIS) is a powerful technique that can be used to elicit information about an electrode interface. In this article, we highlight six principal processes by which the presence of microorganisms can affect impedance and show how one of these - the production of electroactive metabolites - changes the impedance signature of culture media containing Pseudomonas aeruginosa. EIS, was used in conjunction with a low cost screen printed carbon sensor to detect the presence of P. aeruginosa when grown in isolation or as part of a polymicrobial infection with Staphylococcus aureus. By comparing the electrode to a starting measurement, we were able to identify an impedance signature characteristic of P. aeruginosa. Furthermore, we are able to show that one of the changes in the impedance signature is due to pyocyanin and associated phenazine compounds. The findings of this study indicate that it might be possible to develop a low cost sensor for the detection of P. aeruginosa in important point of care diagnostic applications. In particular, we suggest that a development of the device described here could be used in a polymicrobial clinical sample such as sputum from a CF patient to detect P. aeruginosa.
Highlights
Electrochemical Impedance Spectroscopy (EIS) has been investigated extensively as a tool for the detection of microbial attachment and biofilm formation [1,2,3,4,5,6,7,8,9,10,11]
It was found that specific impedance signatures could be discerned between control electrodes and those inoculated with S. aureus once growth increased above 56107 CFU/ml
We have investigated the application of EIS to a label-less, low cost screen printed sensor for the detection of P. aeruginosa and have elucidated at least one of the causes for the observed changes in impedance
Summary
Electrochemical Impedance Spectroscopy (EIS) has been investigated extensively as a tool for the detection of microbial attachment and biofilm formation [1,2,3,4,5,6,7,8,9,10,11]. One example is the use of EIS in conjunction with a low cost screen printed electrode to detect the level of moisture in chronic wounds, without the need to remove the dressing This device minimises the need to disrupt the dressing unnecessarily reducing patient discomfort and enhancing clinical practice decisions about dressing replacement [12]. These wound moisture sensors have been investigated in the context of wound infection to determine if it is possible to detect different strains of Staphylococcus aureus growing in a suspension in Mueller-Hinton Broth with different concentrations of glucose [13]. It was found that specific impedance signatures could be discerned between control electrodes and those inoculated with S. aureus once growth increased above 56107 CFU/ml
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