Abstract
Pseudomonas aeruginosa is one of the most virulent nosocomial pathogens worldwide. Quorum sensing (QS) regulates the production of pathogenic virulence factors and biofilm formation in P. aeruginosa. The four genes lasR, lasI, rhlR,and rhlI were found to regulate this QS system. In this study, we aimed to assess the correlation between these four genes and QS-dependent virulence factors and to detect the inhibitory effect of clove oil on QS. Fifty P. aeruginosa clinical isolates were collected. Susceptibility to different antibiotics was tested. Virulence factors including biofilm formation, pyocyanin production, and twitching motility were phenotypically detected. QS genes were amplified by polymerase chain reaction (PCR), and one strain subsequently underwent sequencing. The inhibitory effect of clove oil on virulence factors was also tested. A positive correlation was found between biofilm formation and the presence of lasR and rhlI genes. Twitching motility was positively correlated with the presence of lasR, lasI, and rhlI genes. On the other hand, no correlation was found between pyocyanin production and any of the studied genes. Only one isolate amplified all the tested QS gene primers, but it did not express any of the tested virulence factors phenotypically. Sequence analyses of this isolate showed that the four genes had point mutations. Results emphasize the importance of QS in P. aeruginosa virulence; however, QS-deficient clinical isolates occur and are still capable of causing clinical infections in humans. Also, clove oil has an obvious inhibitory effect on QS, which should be clinically exploited.
Highlights
Pseudomonas aeruginosa is one of the most virulent nosocomial pathogens worldwide
According to the antibiotic disk diffusion method, the highest resistance in the P. aeruginosa clinical isolates was exhibited towards amoxicillin (100%), followed by ampicillin, cefadroxil, cefazolin, cefuroxime, and ampicillin-sulbactam (98% for each), cefoxitine and co-trimoxazole (96% for each), and amoxicillin-clavulanic acid (94%)
We investigated the role of the Quorum sensing (QS) systems in the pathogenesis of P. aeruginosa by screening the presence of three QS-dependent virulence factors in 50 different clinical isolates
Summary
Pseudomonas aeruginosa is one of the most virulent nosocomial pathogens worldwide. Quorum sensing (QS) regulates the production of pathogenic virulence factors and biofilm formation in P. aeruginosa. Pseudomonas aeruginosa is a Gram-negative bacterium found in almost every ecological niche, including soil, water, and plants It is an important opportunistic pathogen of humans, primarily infecting immunocompromised patients such as severely burned patients, patients with cystic fibrosis, and cancer patients undergoing chemotherapy [1]. 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 antibiotic resistance engendered by biofilms presents a serious challenge to the treatment of chronic P. aeruginosa infections [2]
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