Diversity of biofilms produced by quorum-sensing-deficient clinical isolates of Pseudomonas aeruginosa

Abstract

The quorum-sensing (QS) systems control several virulence attributes of Pseudomonas aeruginosa. Five QS-deficient P. aeruginosa clinical isolates (CI) that were obtained from wound (CI-1), tracheal (CI-2, CI-3, CI-4) and urinary tract (CI-5) infections had previously been characterized. In this study, a flow-through continuous-culture system was utilized to examine in detail the biofilms formed by these isolates in comparison with the P. aeruginosa prototrophic strain PAO1. Analysis of the biofilms by confocal laser scanning microscopy and COMSTAT image analysis at 1 and 7 days post-inoculation showed that the isolates produced diverse biofilms. In comparison with PAO1, the CI produced biofilms that scarcely or partially covered the surface at day 1, although CI-1 produced larger microcolonies. At day 7, CI-2 and CI-4 produced mature biofilms denser than that produced by PAO1, while the biofilm formed by CI-1 changed very little from day 1. CI-1 was defective in both swarming and twitching motilities, and immunoblotting analysis confirmed that it produced a reduced level of PilA protein. The twitching-motility defect of CI-1 was not complemented by a plasmid carrying intact pilA. In the 48 h colony biofilm assay, the CI varied in susceptibility to imipenem, gentamicin and piperacillin/ tazobactam. These results suggest that: (1) the isolates produced biofilms with different structures and densities from that of PAO1; (2) biofilm formation by the isolates was not influenced by either the isolation site or the QS deficiencies of the isolates; (3) the behaviour of CI-1 in the different biofilm systems may be due to its lack of swarming motility and type IV pilus-related twitching motility.

Correlation of quorum sensing and virulence factors in Pseudomonas aeruginosa isolates in Egypt

“…The severity of P. aeruginosa infections is due to the production of different extracellular and cellassociated virulence factors including pyocyanin, flagella, and pili [2,3,4]. Another factor contributing to the pathogenesis of P. aeruginosa is its tendency to form organized communities, known as biofilms, when it attaches to biotic and abiotic surfaces [1].…”

“…The biofilms of P. aeruginosa may also be formed on medical devices such as urinary catheters. In these settings, the antibiotic resistance engendered by biofilms presents a serious challenge to the treatment of chronic P. aeruginosa infections [2] Another virulence factor produced by P. aeruginosa is the blue redox-active exoproduct pyocyanin, the predominant phenazine pigment produced by this organism that can easily penetrate biological membranes. It is readily recovered in large quantities from cystic fibrosis patients infected by P. aeruginosa and from ear secretions of P. aeruginosamediated chronic otitis media.…”

Influence of Quorum Sensing and Iron on Twitching Motility and Biofilm Formation in Pseudomonas aeruginosa

“…A number of studies have linked quorum sensing (QS), cell density control of gene expression involving acylhomoserine lactones (acyl-HSLs) (36, 69), and biofilm formation/development in P. aeruginosa (17,26,38,64), although some studies indicate that QS has little or no role, with QS mutants being proficient in biofilm formation (27,62,67,68). These discrepancies are generally linked to differences in biofilm model and/or culture conditions, and indeed, a recent study confirmed that the QS dependence of biofilm formation is nutritionally conditional (i.e., QS systems are needed for biofilm formation in some growth media [e.g., succinate] but not others [e.g., glucose or glutamate]) (73).…”

“…Details of in vivo P. aeruginosa biofilm formation, structure, and properties are limited, with most of our understanding of these structures coming from the study of model biofilms formed in vitro (3,15,29,30,56,80,81,84). In vitro biofilm development in P. aeruginosa is characterized by bacterial surface attachment, followed by microcolony formation by clonal expansion or motility-driven cell-to-cell aggregation and subsequent formation of a flat, uniform, confluent biofilm or heterogeneous, structured biofilms characterized by cell aggregates or "mushroom" structures separated by channels or spaces (38,40).A number of studies have linked quorum sensing (QS), cell density control of gene expression involving acylhomoserine lactones (acyl-HSLs) (36, 69), and biofilm formation/development in P. aeruginosa (17,26,38,64), although some studies indicate that QS has little or no role, with QS mutants being proficient in biofilm formation (27,62,67,68). These discrepancies are generally linked to differences in biofilm model and/or culture conditions, and indeed, a recent study confirmed that the QS dependence of biofilm formation is nutritionally conditional (i.e., QS systems are needed for biofilm formation in some growth media [e.g., succinate] but not others [e.g., glucose or glutamate]) (73).…”

An Organoselenium Compound Inhibits Staphylococcus aureus Biofilms on Hemodialysis Catheters In Vivo

“…Development of S. aureus biofilm on 1-cm catheter segments was achieved using a multicell flowthrough continuous-culture system (5,31). Catheter segments were secured in the flow cell with stainless steel brackets, the flow cells were attached to silicone tubing, and these units were sterilized by autoclaving.…”