Investigating the role of ndvB in Pseudomonas aeruginosa biofilms

Abstract

Pseudomonas aeruginosa is an opportunistic pathogen prevalent in nosocomial infections and patients with cystic fibrosis. P. aeruginosa shows a high degree of antibiotic tolerance which in part can be attributed to the formation of biofilms. The increased antibiotic resistance seen in biofilms can be attributed to several factors including differential gene expression within biofilms that can lead to biofilm specific mechanisims of antibiotic resistance. The ndvB gene is important for biofilm specific antibiotic resistance in P. aeruginosa. It is important in signaling and regulation of gene expression in other pathogens. Microarray analysis comparing gene expression between wildtype and a ndvB deletion mutant was performed to identify genes that might be regulated by the gene product, believed to be cyclic glucans, that contribute to biofilm specific antibiotic resistance. The array analysis identified 24 genes that were differentially regulated by ndvB, including a response regulator, agmR, as well as most of the genes which it regulates. Quantitative real-time polymerase chain reactions using primers specific to agmR and its associated genes confirmed that they were expressed in a ndvB related manner. Minimal bactericidal concentration assays were performed and confirmed that these genes are important in resistance to tobramycin and ciprofloxacin.