The activity of efflux inhibitors, such as diamine compounds, has been demonstrated in animal models of P. aeruginosa infections and two of them are in preclinical development [26]. In B. cenocepacia the significance of RND efflux

systems has not been determined. However, a salicylate-regulated efflux pump that is conserved among members of the Bcc has been identified [27, 28]. We are focusing our research in the B. cenocepacia J2315 strain. This strain is a prototypic isolate belonging to an epidemic clone that has spread by cross infection to CF patients in Europe and North America [29]. Previously, we identified 14 genes encoding putative RND efflux pumps Barasertib price in the genome of B. cenocepacia J2315 [30]. After the completion of the whole genome sequence [31], two additional genes encoding RND pumps TSA HDAC ic50 were discovered. Reverse transcriptase analyses showed that some of these genes are indeed transcribed at detectable levels.

As a first step towards understanding the contribution of RND pumps to B. cenocepacia antibiotic resistance we deleted genes encoding putative efflux pumps, RND-1, RND-3, and RND-4, containing the genes BCAS0591-BCAS0593 (located on chromosome 3), BCAL1674-BCAL1676, and BCAL2822-BCAL2820 (located on chromosome 1), respectively. In a previous publication, the genes encoding the membrane transporter component of the efflux pump, BCAS0592, BCAL1675, and BCAL2821 were referred to as Orf1, Orf3, and Orf4, respectively [30]. In this investigation we show that deletion of rnd-3 and rnd-4 genes is associated with increased sensitivity to certain antibiotics and reduced secretion of quorum sensing molecules. Results and Discussion B. either cenocepacia BCAS0592, BCAL1675, and BCAL2821 encode RND-type transporters We characterized 3 efflux systems of B. cenocepacia J2315 by deletion mutagenesis. These systems were selected based on

their high homology to the well-characterized Mex efflux pumps in P. aeruginosa. One of the identified operons, located on chromosome 3, encodes RND-1 and comprises the genes BCAS0591-BCAS0592-BCAS0593 that span nucleotides 645029 to 650880 [Fig. 1]. BCAS0591 encodes a predicted 418-aa membrane fusion protein, followed by the RND transporter gene predicted to encode a 1065-aa protein, and BCAS0593 encoding a 475-aa outer membrane protein. Amino acid sequence analysis of the BCAS0592 gene product revealed conserved motifs and the characteristic predicted structure common to the inner membrane proteins of the RND efflux complex. Topologically BCAS0592 is a polypeptide with 12 predicted transmembrane alpha helices and two large periplasmic loops between transmembrane helices 1-2 and 7-8 [30].