Detection of Escherichia coli in Drinking Water Using T7 Bacteriophage-Conjugated Magnetic Probe

Abstract

In this study, we demonstrate a bacteriophage (phage)-based magnetic separation scheme for the rapid detection of Escherichia coli (E. coli) in drinking water. T7 phage is a lytic phage with a broad host range specificity for E. coli. Our scheme was as follows: (1) T7 bacteriophage-conjugated magnetic beads were used to capture and separate E. coli BL21 from drinking water; (2) subsequent phage-mediated lysis was used to release endemic β-galactosidase (β-gal) from the bound bacterial cells; (3) the release of β-gal was detected using chlorophenol red-β-d-galactopyranoside (CRPG), a colorimetric substrate which changes from yellow to red in the presence of β-gal. Using this strategy, we were able to detect E. coli at a concentration of 1 × 10(4) CFU·mL(-1) within 2.5 h. The specificity of the proposed magnetic probes toward E. coli was demonstrated against a background of competing bacteria. By incorporating a pre-enrichment step in Luria-Bertani (LB) broth supplemented with isopropyl β-d-thiogalactopyranoside (IPTG), we were able to detect 10 CFU·mL(-1) in drinking water after 6 h of pre-enrichment. The colorimetric change can be determined either by visual observation or with a reader, allowing for a simple, rapid quantification of E. coli in resource-limited settings.

Enzymatic Digestion for Improved Bacteria Separation from Leafy Green Vegetables

“…Immunomagnetic separation (IMS) is another prevalent method for a relatively rapid, clean and specific separation of bacteria from liquid food samples, such as milk and juice. The IMS technique uses magnetic beads (1-5 μm) conjugated with specific antibodies which adhere to the bacterial cells and thus help to separate the bacteria in the presence of a strong magnetic field (12,60). Following aspiration of the supernatant, the bead-analyte conjugates are re-suspended in a buffer and used for detection.…”

Integrating recognition elements with nanomaterials for bacteria sensing

“…These methods have successfully detected several pathogenic bacteria. 39 Taking advantage of the high surface-to-volume ratio of MNPs, Chen et al . fabricated T7 phage-based magnetic FeCo nanoprobes for bacteria separation.…”

Bacteriophages and their applications

“…Besides, bacteriophages covalently attached with a fluorescent dye to their coats can be employed for the detection of specific adsorption (Goodridge et al, 1999). In certain cases, detection of other released components, which include adenosine triphosphate (ATP), adenylate kinase (AK) and β-D -galactosidase after the specific lysis of bacteria can also be used (Guzmán Luna et al, 2009;Lee et al, 2011;Chen et al, 2015).…”