The majority of these virulence factors include proteases produced under control of the Las and Rhl quorum sensing systems of P. aeruginosa, examples of which include LasA and LasB elastases and AbMole Capromorelin tartrate alkaline protease. These proteases play an important role in P. aeruginosa pathogenesis through the degradation of biologically active proteins present in human tissue. In fact, the significant role of the QS-system in P. aeruginosa-related disease progression has resulted in much research into QS-inhibiting compounds that could potentially reduce the organism’s virulence potential. Further, the therapeutic efficacy 
of this anti-QS, anti-virulence, strategy in the treatment of P. aeruginosa has already been demonstrated for the QS-inhibiting antibiotic azithromycin. Though antivirulence treatment based on QS-inhibition is only useful when an active, virulence factor secreting, QS-system is present in the P. aeruginosa strain to be targeted. In this study we describe the design of a novel P. aeruginosa-specific Fluorescence Resonance Energy AbMole Aristolochic-acid-A Transfer-peptide substrate and examine its applicability for the detection of P. aeruginosa proteolytic activity in clinical specimens. In addition, we studied the link between substrate cleavage efficiency, virulence factor production and susceptibility towards QS-inhibiting antibiotics, such as azithromycin. We designed and evaluated a fluorogenic substrate as a potential marker of virulence in the bacterial pathogen P. aeruginosa. Preliminary experiments indicated that this 3xGly substrate was specific for cleavage by P. aeruginosa, and that the sensitivity of the substrate was 107 CFU/ml within 1 h, though this limit of detection may vary among different P. aeruginosa strains. Only slight cross reactivity was observed with another bacterial protease, lysostaphin, which recognizes and degrades pentaglycin bonds. Later experiments using a broader range of 97 clinical isolates showed that 3xGly cleavage activity differed between P. aeruginosa isolates, with a large percentage of the isolates being unable to cleave the 3xGly substrate. This is possibly related to difference in expression of the P. aeruginosa QSsystem. We indeed observed a slight, but non-significant, decrease in expression of the QS-genes lasI and rhlI in P. aeruginosa strains which lacked 3xGly proteolytic activity. Because this experiment was performed with a subset of the P. aeruginosa strains future experiments are required in order to identify the exact genetic basis of the proteolysis / virulence correlation. One of the most important proteases secreted under the direction of the P. aeruginosa QS system is the LasA protease. The LasA protease of P. aeruginosa can recognize and degrade glycine bonds, degrade elastin and is an important contributor to the pathogenesis of this organism.