Down-regulatory effects of green coffee extract on las I and las R virulence-associated genes in Pseudomonas aeruginosa
Antibiotic resistant strains of Pseudomonas aeruginosa are the cause of Gram negative nosocomial infections especially among the immunosuppressed patients. The bacteria contains las I and las R genes that play very important roles in the pathogenesis and mechanisms of aggression. These genes can be influenced by the quorum sensing (QS) system and such mechanism is becoming clinically important worldwide. This study aimed to investigate the preventive effects of green coffee extract (GCE) on the expression of pathogenesis-related genes, las I and las R in P. aeruginosa.
A total of fifty four P. aeruginosa strains were isolated out of 100 clinical samples collected from the infectious wards in different hospitals (Tehran province) using conventional microscopic and biochemical methods. Susceptibility of the isolates to different antibiotics, GCE and chlorogenic acid were elucidated. Multiplex polymerase chain reaction (PCR) and real-time PCR were performed to detect and quantify the expression levels of las I and las R genes. The presence of chlorogenic acid in GCE was confirmed by HPLC.
Antibiotic susceptibility tests revealed multidrug resistance among the clinical isolates of those 40 strains were resistant to ciprofloxacin (74.07%), 43 to ceftazidime (79.26%), 29 to amikacin (53.7%), 42 to ampicillin (77.77%), 17 to colistin (31.48%), 40 to gentamicin (74.77%), and 50 to piperacillin (92.59%). PCR outcomes exhibited that the frequency of las I and las R genes were 100% in resistant and sensitive strains isolated from clinical and standard strains of P. aeruginosa (ATCC 15449). Real-time PCR analyses revealed that GCE significantly prevented the expression of las I and las R genes in P. aeruginosa. GCE at concentration level as low as 2.5 mg/mL could prevent the expression of lasI and lasR genes in P. aeruginosa clinical isolates.
The presence and expression levels of las I and las R genes in P. aeruginosa isolates were investigated when the bacteria was exposed to GCE. Our results tend to suggest that genes involved in pathogenesis of: Pseudomonas aeruginosa are down regulated by quorum sensing effect of chlorogenic acid and therefore GCE could be useful as an adjuvant in combating multidrug resistance strains of Pseudomonas aeruginosa.
KeywordsPseudomonas aeruginosa Chlorogenic acid Green coffee extract Quorum sensing
This study was PhD thesis of HJ who did all the practical experiments. HJ contributed in the conception, design of the study, data collation and manuscript preparation. NS contributed in the conception and the design of the study. JN contributed in the design of the study. MD supervised the gene analysis experiments. MRF contributed in the conception, the design of the study and gave revisions of the manuscript. All authors read and approved the final manuscript.
This research was supported by Deputy of Research, Tehran University of Medical Sciences, (grant No. 31002).
Compliance with ethical standards
This study was approved by the Ethics Committee of the Tehran University of Medical Sciences, Tehran, Iran (ethics committee reference number: IR. TUMS. REC. 1394.2108).
The authors declare that they have no competing interest.
Ethics approval and consent to participate
Consent for publication
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