Rapid detection and identification of bacteria: SEnsing of Phage-Triggered Ion Cascade (SEPTIC)
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Methods for the rapid detection and identification of bacteria are urgently needed. Here we describe a method that combines the specificity and avidity of bacteriophages with fluctuation analysis of electrical noise. The method is based on the massive transitory ion leakage that occurs at the moment of phage DNA injection into the host cell. The ion fluxes require only that the cells be physiologically viable (i.e. have energized membranes) and can occur within seconds after mixing the cells with sufficient concentrations of phage particles. To detect these fluxes, we have constructed a nano-well, a lateral, micrometer-sized capacitor of titanium electrodes with gap size of 150 nm, and used it to measure the electrical field fluctuations in microlitre (mm3) samples containing phage and bacteria. In mixtures where the analyte bacteria were sensitive to the phage, large stochastic waves with various time and amplitude scales were observed, with power spectra approximately following a 1/f2 law from 1-10 Hz. Development of this SEPTIC (SEnsing of Phage-Triggered Ion Cascades) technology could provide rapid detection and identification of live pathogenic bacteria on the scale of minutes, with unparalleled specificity. The method has a potential ultimate sensitivity of 1 bacterium/microlitre (1 bacterium/mm3).
