Selective capture and identification of pathogenic bacteria using an immobilized siderophore

Rapid identification of infectious pathogens constitutes an important step toward limiting the spread of contagious diseases. Whereas antibody-based detection strategies are often selected because of their speed, mutation of the pathogen can render such tests obsolete. In an effort to develop a rapid yet mutation-proof method for pathogen identification, we have explored the use of "immutable ligands" to capture the desired microbe on a detection device. In this "proof-of-principle" study, we immobilize pyoverdine, a siderophore that Pseudomonas aeruginosa must bind to obtain iron, onto gold-plated glass chips and then examine the siderophore's ability to capture P. aeruginosa for its subsequent identification. We demonstrate that exposure of pyoverdine-coated chips to increasing dilutions of P. aeruginosa allows detection of the bacterium down to concentrations as low as 102/mL. We further demonstrate that printing of the siderophore in a periodic pattern on the detection chip enables a sensitive method of detecting the bound pathogen by a Fourier transform analysis of light scattered by the patterned chip. Because unrelated bacteria are not captured on the pyoverdine chip, we conclude that pyoverdine can be exploited for the specific binding and identification of P. aeruginosa. It follows that the utilization of other microbe-specific "immutable ligands" may allow the specific identification of their cognate pathogens.