Dark Field Microscopy-Based Biosensors for the Detection of E. coli in Environmental Water Samples

• Published in: Sensors (Basel, Switzerland) Vol. 19; no. 21; p. 4652
• Main Authors: La Spina, Rita, António, Diana C, Desmet, Cloe, Valsesia, Andrea, Bombera, Radoslaw, Norlén, Hedvig, Lettieri, Teresa, Colpo, Pascal
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 26.10.2019; MDPI
• Subjects: Antibodies; Bacillus - immunology; Bacteria; bacteria quantification; Biosensors; Calibration; Cells, Immobilized - metabolism; dark field microscopy; Drinking water; E coli; Escherichia coli - genetics; Escherichia coli - immunology; Escherichia coli - isolation & purification; Experiments; field water samples; Microorganisms; Microscopy; Microscopy - instrumentation; Microscopy - methods; Polymerase chain reaction; Reproducibility of Results; Sensitivity and Specificity; Sensors; Serum albumin; Silicon wafers; Surface Plasmon Resonance; Waste Water - microbiology; Wastewater treatment; Water distribution; Water engineering; Water Microbiology; Water sampling; Water treatment; Italy; Germany; dark field microscopy; antibodies; field water samples; bacteria quantification
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s19214652

Development of sensitive methods for the determination of bacteria contamination in water distribution systems is of paramount importance to ensure the microbial safety of drinking water. This work presents a new sensing platform enabling the fast detection of bacteria in field samples by using specific antibodies as the biorecognition element and dark field microscopy as the detection technique. The development of the sensing platform was performed using non-pathogenic bacteria, with the DH5α strain as the target, and 9727 as the negative control. The identification of the captured bacteria was made by analyzing the dark field microscopy images and screening the detected objects by using object circularity and size parameters. Specificity tests revealed the low unspecific attachment of either over human serum albumin antibodies (negative control for antibody specificity) and of . over antibodies. The system performance was tested using field samples, collected from a wastewater treatment plant, and compared with two quantification techniques (i.e., Colilert-18 test and quantitative polymerase chain reaction (qPCR)). The results showed comparable quantification capability. Nevertheless, the present method has the advantage of being faster, is easily adaptable to in-field analysis, and can potentially be extended to the detection of other bacterial strains.