β-Alanyl aminopeptidase-activated fluorogenic probes for the rapid identification of Pseudomonas aeruginosa in clinical samples

Abstract

The fluorogenic self-immolative substrates 8 are specifically hydrolyzed by β-alanyl aminopeptidase, resulting in a 1,6-elimination and the release of the highly fluorescent hydroxycoumarins 6. 7-{4-(β-Alanylamino)}benzyloxy-3-ethoxycarbonylcoumarin trifluoroacetate 8b has advantages over another fluorogenic substrate, 7-N-β-alanylamino-4-methylcoumarin 9, as it is retained by bacterial colonies in solid agar applications, and results in similar times to detection, stronger fluorescence intensities, and no decrease in signal over time in liquid media. Although 7-{4-(β-alanylamino)}benzyloxy-4-methylcoumarin trifluoroacetate 8a produces a weaker signal than substrate 8b, its use allowed better discrimination between the BAP producers P. aeruginosa (positive) and S. marcescens (negative).