Sensitive detection of live Escherichia coli by bacteriophage amplification-coupled immunoassay on the Luminex® MAGPIX instrument.

Phages are natural predators of bacteria and have been exploited in bacterial detection because of their exquisite specificity to their cognate bacterial hosts. In this study, we present a "proof of concept" bacteriophage amplification-coupled assay as a surrogate for detecting a bacterium present in a sample. The assay entails detection of progeny phage resulting from infection and subsequent growth inside the bacterium present in suspected samples. This approach reduces testing time and enhances sensitivity to identify pathogens compared to traditional overnight plaque assay. Further, the assay has the ability to discriminate between live and dead cells since phages require live host cells to infect and replicate. To demonstrate its utility, phage MS2 amplification-coupled, bead-based sandwich type immunoassay on the Luminex® MAGPIX instrument for Escherichia coli detection was performed. The assay not only showed live cell discrimination ability but also a limit of E. coli detection of 1 × 102 cells/mL of live cells after a 3-h incubation. In addition, the sensitivity of the assay was not impaired in the presence of dead cells. These results demonstrate that bacteriophage amplification-coupled assay can be a rapid live cell detection assay compared to traditional culture methods and a promising tool for quick validation of bacterial inactivation. Combined with the unique multiplex bead chemistry of the Luminex® MAGPIX platform, the phage assay can be expanded to be an ultra-deep multiplex assay for the simultaneous detection of multiple pathogens using specific phages directed against the target pathogens.

Fgf19 is required for zebrafish lens and retina development.

Fgf signaling plays crucial roles in morphogenesis. Fgf19 is required for zebrafish forebrain development. Here, we examined the roles of Fgf19 in the formation of the lens and retina in zebrafish. Knockdown of Fgf19 caused a size reduction of the lens and the retina, failure of closure of the choroids fissure, and a progressive expansion of the retinal tissue to the midline of the forebrain. Fgf19 expressed in the nasal retina and lens was involved in cell survival but not cell proliferation during embryonic lens and retina development. Fgf19 was essential for the differentiation of lens fiber cells in the lens but not for the neuronal differentiation and lamination in the retina. Loss of nasal fate in the retina caused by the knockdown of Fgf19, expansion of nasal fate in the retina caused by the overexpression of Fgf19 and eye transplantation indicated that Fgf19 in the retina was crucial for the nasal-temporal patterning of the retina that is critical for the guidance of retinal ganglion cell axons. Knockdown of Fgf19 also caused incorrect axon pathfinding. The present findings indicate that Fgf19 positively regulates the patterning and growth of the retina, and the differentiation and growth of the lens in zebrafish.