Photoaffinity Approach Reveals Antibiotic Adjuvant Activity toward Pseudomonas aeruginosa

Pseudomonas aeruginosa is an emerging public health threat. A common Gram‐negative source of secondary infections, it has few effective treatment options, which are currently being undermined by the rise of resistance. New therapies are urgently needed. We had previously pursued an antivirulence strategy to block the production of pyocyanin, a redox‐active virulence factor. A photoaffinity analog of an antipyocyanin compound was developed to interrogate the inhibitor’s molecular mechanism of action. In the process, antibiotic adjuvant activity was suggested by the proteomics results. Using susceptibility assays, we found that these compounds amplify the bactericidal activity of colistin, a well‐characterized antibiotic, suggesting they may represent a first‐in‐class antibiotic adjuvant therapy. Analogs have the potential to not only widen the therapeutic index of cationic antibiotic peptides like colistin, but to be effective against colistin‐resistant strains. Multidrug‐resistant infections with P. aeruginosa are currently treated with colistin and the related polymyxin b, however, resistance to these drugs is also increasingly encountered. The adjuvants have the potential to preserve the life‐saving therapy of colistin when used in a combination therapy.