Rapid detection of Escherichia coli in water by a culture-based amperometric method

An amperometric culture-based method was developed for rapid detection of viable Escherichia coli in water. The bacteria were recovered by filtration and incubated in a selective medium, lauryl sulphate broth (LSB) supplemented with the substrate 4-aminophenyl-beta -D-galactopyranoside (4-APGal) at 44.5 degreesC. The electrochemically active molecule 4-aminophenol (4-AP) was produced after hydrolysis of 4-APGal by the enzyme beta -galactosidase. 4-AP was measured by amperometry and was detected at a due concentration of E. coli. The time necessary for reaching that concentration was inversely related to the initial E. coli concentration of the sample. Environmental samples and suspensions of E coli IT1 were assayed. 4-AP was detected after 7.3 and 2.0 h in samples containing initial concentrations of E. coli IT1 of 4.5 and 4.5 x 10(6) cfu ml(-1), respectively. For environmental samples with initial E. coli concentrations of 1.0 and 2.0 x 10(3) cfu ml(-1),4-AP were detected after 10 and 6.6 h, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.