Antibacterial and Antivirulence Activity of Glucocorticoid PYED-1 against Stenotrophomonas maltophilia

, an environmental Gram-negative bacterium, is an emerging nosocomial opportunistic pathogen that causes life-threatening infections in immunocompromised patients and chronic pulmonary infections in cystic fibrosis patients. Due to increasing resistance to multiple classes of antibiotics, infections are difficult to treat successfully. This makes the search for new antimicrobial strategies mandatory. In this study, the antibacterial activity of the heterocyclic corticosteroid deflazacort and several of its synthetic precursors was tested against . All compounds were not active against standard strain K279a. The compound PYED-1 (pregnadiene-11-hydroxy-16α,17α-epoxy-3,20-dione-1) showed a weak effect against some clinical isolates, but exhibited a synergistic effect with aminoglycosides. PYED-1 at sub-inhibitory concentrations decreased biofilm formation. Quantitative real-time polymerase chain reaction (RT-qPCR) analysis demonstrated that the expression of biofilm- and virulence- associated genes ( , , , , , ) was significantly suppressed after PYED-1 treatment. Interestingly, PYED-1 also repressed the expression of the genes (3´)-IIc, (6´)-Iz, and , involved in the resistance to aminoglycosides.