In this paper we present economical interdigitated flexible sensor on the paper substrate for bacteria detection. The impedance measurement was performed in the frequency range of 12.6 kHz–100 kHz for the suspensions with cell density of $1.5\cdot 10^{8}$ CFU/mL, $1.5\cdot 10^{5}$ CFU/mL and $1.5\cdot 10^{2}$ CFU/mL of Pseudomonas aeruginosa and Staphylococcus aureus bacteria, as well as for a sterile saline. Using the measured impedance data, we observed that sensor impedance magnitude increases when bacteria concentration increases. Moreover, impedance spectroscopic analysis was carried out to identify an equivalent electrical circuit for the sensor modelling. Through statistical analysis it was found that all model parameters changes according to the bacteria type and concentration. Additionally, obtained results showed that all fittings results in root mean square errors lower than $0.072~\Omega $ for impedance magnitude, and 0.157° for impedance phase angle.