Electrochemical recognition and quantification of cytochrome c oxidase expression in bacteria

A method of determining the presence of bacteria expressing cytochrome c oxidase comprising: providing a sample suspected of containing the bacteria; providing a compound that has two redox states: a reduced state and an oxidised state, wherein cytochrome c oxidase can convert the compound from its reduced state to its oxidised state; contacting an electrode either with the compound in its oxidised state in the presence of the sample, then applying a reductive potential and measuring the current at the electrode; or the compound in its reduced state in the presence of the sample, then applying an oxidative potential and measuring the current at the electrode; and comparing the magnitude of the current produced by the reductive potential or oxidative potential in the presence of the sample suspected of containing the bacteria with the magnitude of the current produced under the same conditions, but in the absence of the sample suspected of containing the bacteria, wherein a difference between the magnitude of current produced in the presence of the sample suspected of containing the bacteria and the magnitude of current produced in the absence of the sample suspected of containing the bacteria indicates the presence of the bacteria. Also provided is an electrochemical sensor for determining the presence of bacteria expressing cytochrome c oxidase.