title: Amperometric detection of Enterobacteriaceae in river water by measuring β-galactosidase activity at interdigitated microelectrode arrays.
abstract: Two simple methodologies are compared for the detection of faecal contamination in water using amperometry at gold interdigitated microelectrodes. They rely on the detection of β-galactosidase (β-gal) by redox cycling amperometry of the p-aminophenol (PAP) produced by the enzyme from the 4-aminophenyl β-d-galactopyranoside (PAPG) substrate. The use of phages as specific agents for the release of the bacteria-enclosed enzyme allowed the detection of 6×10(5) CFU mL(-1)Escherichia coli in 2 h without any pre-enrichment or preconcentration steps. Better limits of detection were achieved for the second strategy in the absence of phages. In this case, bacteria were enriched in the presence of both β-d-1-thiogalactopyranoside (IPTG) and substrate but in the absence of phages. Under such experimental conditions, 5×10(4) CFU mL(-1) E. coli could be detected after 2 h of incubation, while 7 h of incubation were enough to detect down to 10 CFU mL(-1) in river water samples. This represents a straightforward one-step method for the detection of faecal contamination that can be conducted in a single working day with minimal sample manipulation by the user.
authors.affiliation: Institut de Microelectrònica de Barcelona, (IMB-CNM), CSIC, Campus UAB, 08193, Bellaterra, Barcelona, Spain.
authors.forename: Olivier
authors.initials: O
authors.lastname: Laczka
authors.forename: Cristina
authors.initials: C
authors.lastname: García-Aljaro
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: del Campo
authors.forename: Francesc Xavier
authors.initials: FX
authors.lastname: Muñoz Pascual
authors.forename: Jordi
authors.initials: J
authors.lastname: Mas-Gordi
authors.forename: Eva
authors.initials: E
authors.lastname: Baldrich
mesh_terms: D000627:Aminophenols / Q000032:analysis / Q000737:chemistry; D015374:Biosensing Techniques / Q000379:methods*; D004563:Electrochemistry; D004755:Enterobacteriaceae / Q000201:enzymology / Q000302:isolation & purification*; D005960:Glucosides / Q000378:metabolism; D057230:Limit of Detection; D008839:Microelectrodes; D010084:Oxidation-Reduction; D045483:Rivers / Q000737:chemistry*; D013997:Time Factors; D014871:Water Microbiology; D014881:Water Supply / Q000032:analysis* / Q000592:standards; D001616:beta-Galactosidase / Q000032:analysis* / Q000378:metabolism
chemical_list: D000627:Aminophenols; D005960:Glucosides; C055234:4-aminophenyl glucoside; D001616:beta-Galactosidase; C026729:4-aminophenol