Novel enzyme-oligodeoxynucleotide conjugate was synthesized to improve sensitivity of Escherichia coli 16S rRNA detection on gold electrodes. Thermostable esterase 2 from Alicyclobacillus acidocaldarius was multiply conjugated to a polyamidoamine dendrimer functionalized by one universal detector oligodeoxynucleotide. Three components rRNA/DNA hybridization between capture oligodeoxynucleotide covalently immobilized on a gold electrode, 16S rRNA and the multivalent esterase-dendrimer cluster was used for detection of E. coli. The linear dependence of the electrochemical signals to analyte concentration revealed a detection limit of 50 colony forming units E. coli, which represents a tenfold signal enhancement if compared to the detection limit achieved with monovalent esterase-oligodeoxynucleotide conjugate.