Quorum Sensing and Biofilm Formation by Burkholderia contaminans Clinical Isolates Obtained from Cystic Fibrosis Patients Chronically Infected.

PABLO MARTINA, CLAUDIA PRIETO,DAMIAN MARINO, MARISA BETTIOL, PATRICIA MONTANARO, CECILIA BAEZA, MARÍA EUGENIA ZAPPA, ALEJANDRA BOSCH AND OSVALDO YANTORNO

Mar del Plata

Congreso; VIII Congreso Argentino de Microbiología General; 2012

Soceidad Argentina de Microbiología General

Burkholderia cepacia complex (Bcc) comprises Gram-negative bacteria capable of causing chronic and often severe respiratory tract infections in cystic fibrosis (CF) patients and various infections in inmunocompromised non-CF patients. The chain of events leading to the establishment of a persistent infection is mainly due to the biofilm forming capacity of these microorganisms. In the case of Pseudomonas aeruginosa one of the major lung colonizers of CF patients, it was reported that when the chronic infection becomes established, the strains differ phenotypically from the intermittent strains. Dominating changes like the switch to mucoidity (alginate overproduction) and loss of epigenetic regulation of virulence through the Quorum Sensing (QS) system have been described. QS relies on the production and release of small molecule signals by the bacterium into its environment. These signals have also been termed “autoinducers” and bacterial “pheromones.” In Gram-negative bacteria, a typical QS system usually involves the production and response to an acylated homoserine lactone (AHL) molecule. The aim of this work was first to study the QS signals expressed by B. contaminans (one of the 17 species of the Bcc of highest incidence in our country), clinical and environmental isolates. Secondly, we comparatively analyzed the expression of the QS signals and their influence in biofilm formation, among isolates recovered sequentially during long-term lung infections in CF patients suffering chronic infections. For the screening of QS signals expression 45 clinical isolates from CF patients; 10 isolates retrieved from non-CF patients, and 5 isolates obtained from environmental samples were investigated using biosensors and HPLC-MS. Biofilm formation was evaluated by crystal violet stain using micro-titer plate assays and continuous flow chambers. Two Acyl homoserine lactones (AHLs), namely N-octanoylhomoserine lactone (C8-HSL) and N-hexanoylhomoserine lactone (C10-HSL) were the main QS signals found for B. contaminans. The comparative study performed on isolates recovered from subsequent expression chronic infections yielded different scenarios, regarding the expression of acyl-HSL- quorum sensing signals and biofilm formation.