The antioxidant and antibacterial activities, and total phenolic contents of Rosa damascena Mill. flower extracts (absolute, essential oil and hydrosol) were investigated. The chemical compositions of these extracts were analysed by GC-MS. Phenylethyl alcohol (78.38%) was found to be the main constituent of rose absolute, while citrenellol and geraniol were the major compounds (>55%) of rose essential oil and hydrosol. Tocopherol and carotene levels were determined by high performance liquid chromatography (HPLC) analysis. The levels of beta carotene (422.3+/-35.6 ppm), alpha tocopherol (2397.1+/-72.5 ppm) and gamma tocopherol (343.1+/-28.4 ppm) of rose absolute were found to be higher than that of essential oil and hydrosol. Their total phenolic contents were also evaluated. The total phenolic content of the tested extracts varied from 5.2 to 2134.3 GAE/mg L(-1). Rose absolute and essential oil contained high levels of phenolics and demonstrated strong antibacterial activity against Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Bacillus subtilis (ATCC 6633), Staphylococcus aureus (ATCC 6538), Chromobacterium violaceum (ATCC 12472) and Erwinia carotovora (ATCC 39048) strains.

Introduction: In the opportunistic pathogen Pseudomonas aeruginosa, the production of several virulence factors depends on quorum sensing (QS) involving N-acylhomoserine lactone signal molecules. In vitro studies have suggested that the QS system is crucial in the pathogenesis of P. aeruginosa. However, it is unclear whether QS systems of P. aeruginosa play the same role during infections. Methodology: In this study, to explore the contribution of QS systems to the pathogenesis of P. aeruginosa during urinary tract infections, we collected 82 clinical isolates. Detection of N-acyl-homoserine lactones (C12-HSL and C4-HSL) was performed on agar plates employing biosensor strains C. violaceum. Elastase and biofilm production were determined spectrophotometrically. QS genes were detected by PCR and subsequently underwent sequencing. Results and conclusion: Six isolates were found to be negative in the production of both C12-HSL and C4-HSL and all virulence factors tested. PCR analysis of these isolates revealed that four isolates contained all four QS genes while one isolate was negative for lasR gene, and one isolate negative for lasI, lasR and rhlR genes. Sequence analyses of these isolates showed that the lasR, lasI, rhlR and rhlI genes had point mutations. The combination of these mutations probably explains their C12-HSL, C4-HSL and virulence factor deficiencies. Results of this study suggest that QS deficient clinical isolates occur and are still capable of causing clinical infections in humans.

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Many Gram-negative bacteria use N-acyl homoserine lactone signal molecules to monitor their own population density and coordinate gene regulation in a process called quorum sensing (QS). Increasing evidence implies that certain eukaryotes produce QS-inhibitory compounds. In this work, we tested 46 terrestrial plants materials for their ability to inhibit QS-regulated behaviors in different bacterial species. Plant materials were dried and extracted using different solvents. The chloroform-soluble compounds extracted from Scorzonera sandrasica were found to inhibit violacein production, a QS-regulated behavior in Chromobacterium violaceum. In addition, the chloroform extract was also able to inhibit QS-regulated carbapenem antibiotic production in Erwinia carotovora. Because the regulation of many bacterial processes is controlled by QS systems, the finding of natural compounds acting as QS inhibitors suggests an attractive tool to control and handle detrimental infections caused by human, animal, and plant pathogens.

Antibiotics are commonly used for the treatment of microbial infections. With the widespread appearance of multi antibiotic-resistant bacteria, it is becoming increasingly more difficult to treat bacterial infections with conventional antibiotics. Thus, there is an increasing need for new strategies to cope with infectious diseases. The discovery that many pathogenic bacteria employ quorum sensing (QS) to regulate their pathogenicity and virulence factor production makes the QS system an attractive target for antimicrobial therapy. It has been suggested that inactivating the QS system of a pathogen can result in a significant decrease in virulence factor production. In this study, a variety of NSAIDs, such as diclofenac, ibufen, ketoprofen, naproxen, piroxicam were screened for their capacity to reduce the production of QS-regulated virulence factors and swarming motility in the human pathogen P. aeruginosa. Ketoprofen, diclofenac, ibufen, naproxen and piroxicam reduced the elastase production by 28-47% compared to the untreated cultures. Pyocyanin production was also inhibited by these compounds but to a lesser extent. In swarming assay plates, ketoprofen and diclofenac treated PA01 strain displayed significant reductions in swarming motility (81% and 84% respectively). These findings suggest that especially, ketoprofen and diclofenac, may prevent bacterial colonization, and thereby reducing biofilm formation, by interfering with QS-controlled swarming motility of P. aeruginosa and combinatory chemotherapy with both conventional antibiotics and tested NSAIDs could be used for the treatment of chronic infections caused by P. aeruginosa and other clinically important pathogens which regulate their pathogenicity via QS.