Saghar Hendiani1, Majid Pornour2, Nasim Kashef3. 1. Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran. Electronic address: hendiani.s@ut.ac.ir. 2. Department of Photo Healing and Regeneration, Medical Laser Research Center, Yara Institute, Academic Center for Education, Culture and Research (ACECR), Tehran, Iran. Electronic address: pornour@acecr.ac.ir. 3. Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran. Electronic address: kashefn@khayam.ut.ac.ir.
Abstract
BACKGROUND: Photodynamic inactivation (PDI) is recognized as a new antimicrobial approach. It is likely that in human hosts receiving this therapy, pathogens may encounter sub-lethal doses of PDI (sPDI), which may affect microbial virulence. This study was aimed to evaluate the effect of sPDI using methylene blue (MB) on the expression of genes belonging to two quorum sensing (QS) operons (rhl and las systems) and two genes necessary for pyocyanin and rhamnolipid production (phzM and rhlA) under QS control in Pseudomonas aeruginosa. METHODS: Ability of pyocyanin and rhamnolipid production of P. aeruginosa ATCC 27853 and clinical isolates exposed to sPDI (MB at 0.012 mM and light dose of 23 J/cm2 was evaluated. The effect of sPDI on expression of rhlI, rhlR, lasI, lasR, phzM and rhlA were also evaluated by quantitative real time polymerase chain reaction. RESULTS: sPDI led to the down-regulation of the expression of all four QS genes (lasI, lasR, rhlI and rhlR) and rhamnolipid gene (rhlA). However, up-regulation of pyocyanin gene (phzM) was observed after sPDI. These results were consistent with phenotypic changes. CONCLUSION: This study suggests that oxidative stress induced by sPDI can affect QS-regulated virulence factors of P. aeruginosa such as pyocyanin and rhamnolipids in different ways.
BACKGROUND: Photodynamic inactivation (PDI) is recognized as a new antimicrobial approach. It is likely that in human hosts receiving this therapy, pathogens may encounter sub-lethal doses of PDI (sPDI), which may affect microbial virulence. This study was aimed to evaluate the effect of sPDI using methylene blue (MB) on the expression of genes belonging to two quorum sensing (QS) operons (rhl and las systems) and two genes necessary for pyocyanin and rhamnolipid production (phzM and rhlA) under QS control in Pseudomonas aeruginosa. METHODS: Ability of pyocyanin and rhamnolipid production of P. aeruginosa ATCC 27853 and clinical isolates exposed to sPDI (MB at 0.012 mM and light dose of 23 J/cm2 was evaluated. The effect of sPDI on expression of rhlI, rhlR, lasI, lasR, phzM and rhlA were also evaluated by quantitative real time polymerase chain reaction. RESULTS: sPDI led to the down-regulation of the expression of all four QS genes (lasI, lasR, rhlI and rhlR) and rhamnolipid gene (rhlA). However, up-regulation of pyocyanin gene (phzM) was observed after sPDI. These results were consistent with phenotypic changes. CONCLUSION: This study suggests that oxidative stress induced by sPDI can affect QS-regulated virulence factors of P. aeruginosa such as pyocyanin and rhamnolipids in different ways.