Electrochemical detection of the Penicillium chrysogenum mold is carried out in aqueous solution using decreasing resistance of conducting polyaminophenylboric acid. Polymer resistance is calculated on the basis of the data of electrochemical impedance spectroscopy of polymer-modified interdigitated gold microelectrodes with the interelectrode distance of 10 μm. Polymer degradation and the background signal are directed towards an increase in resistance counter to the change in the polymer properties in the presence of microorganisms. Thus, the developed sensor is applicable in practice, as it allows distinguishing the signal of specific binding from nonspecific background processes. The lower limit of microorganism detection was 600 colony-forming units per 1 mL (CFU/mL).