Expression of the las and rhl quorum-sensing systems in clinical isolates of Pseudomonas aeruginosa does not correlate with efflux pump expression or antimicrobial resistance.
OBJECTIVE
Quorum-sensing systems regulate expression of several virulence factors and may affect the MexAB-OprM efflux system in Pseudomonas aeruginosa. This study investigated the relationship between two quorum-sensing systems, efflux pump MexAB-OprM expression and antimicrobial resistance in 33 clinical isolates of P. aeruginosa.


METHODS
Expression of the quorum-sensing regulatory genes lasR and rhlR was assessed by real time RT-PCR. The autoinducer synthetase genes lasI and rhlI and the regulatory genes mexT and mexS were characterized by DNA sequencing. Production of pyocyanin and elastase in each of the isolates was also determined.


RESULTS
While there was a significant correlation between expression of the quorum-sensing regulatory genes and production of pyocyanin and elastase, there was no correlation with expression of mexA or with antimicrobial resistance. There were no mutations in lasI, rhlI, mexT or mexS that correlated with quorum-sensing expression.


CONCLUSIONS
Increased activity of two quorum-sensing systems in P. aeruginosa does not contribute to increased mexA expression or antimicrobial resistance.
Bratu
Simona
S
Division of Infectious Diseases, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
Gupta
Jyoti
J
Quale
John
J
D000222:Adaptation, Physiological; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D001693:Biological Transport, Active; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D008025:Ligases / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010196:Pancreatic Elastase / Q000096:biosynthesis; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D011710:Pyocyanine / Q000096:biosynthesis; D053038:Quorum Sensing / Q000235:genetics; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013223:Statistics as Topic; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C081237:LasI protein, Pseudomonas aeruginosa; C080365:LasR protein, Pseudomonas aeruginosa; D026901:Membrane Transport Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; C086515:RhlR protein, Pseudomonas aeruginosa; D015534:Trans-Activators; D014157:Transcription Factors; D011710:Pyocyanine; D010196:Pancreatic Elastase; D008025:Ligases; C096955:RHLI protein, Pseudomonas aeruginosa