title: The correlation between the presence of quorum sensing, toxin-antitoxin system genes and MIC values with ability of biofilm formation in clinical isolates of Pseudomonas aeruginosa.
abstract: BACKGROUND
  Pseudomonas aeruginosa is a Gram-negative bacterium that considered as important opportunistic human pathogen. One of the mechanisms that help bacteria to tolerate survival in adverse conditions and resistance to antibiotics is biofilm formation through quorum sensing (QS) signals and toxin-antitoxin (TA) systems. QS and TA are two systems that have important roles in biofilm formation. QS is a global regulatory mechanism that enable bacteria to communicate with each other by production of auto inducers (AI) molecules in population. Because of importance biofilm formation in P. aeruginosa infections, here, we studied frequency of QS and TA genes among clinical isolates of P. aeruginosa with ability of biofilm formation.
  
  
  METHODS
  One hundred and forty clinical isolates of P. aeruginosa were collected from Tehran and Ilam hospitals. The isolates were identified by biochemical tests. Biofilm formation was evaluated by microplate method. After DNA extraction by boiling method, the frequency of QS genes (lasIR, rhlIR), and TA genes (mazEF, relBE, hipBA, ccdAB and mqsR) were analyzed by PCR.
  
  
  RESULTS
  Our results showed that maximum resistance is related to aztreonam (72.85%) antibiotic. Most of isolates were able to produce biofilm (87.15%) and the majority of them formed strong biofilm (56.42%). PCR results showed that frequency of mazEF, relBE, hipBA, ccdAB, mqsR, lasIR and rhlIR genes were 85.71, 100, 1.42, 100, 57.14, 93.57 and 83.57 percent, respectively.
  
  
  CONCLUSIONS
  Clinical isolates of P. aeruginosa had high ability to form biofilm, and QS and TA system genes among these isolates were very high (except hipBA genes). There are significaut correlation between biofilm for mation and present of QS and TA system genes.
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Saeed
authors: S
authors: Hemati
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Farid
authors: F
authors: Azizi-Jalilian
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Iraj
authors: I
authors: Pakzad
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Morovat
authors: M
authors: Taherikalani
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Abbas
authors: A
authors: Maleki
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Sajedeh
authors: S
authors: Karimi
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Azam
authors: A
authors: Monjezei
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Zahra
authors: Z
authors: Mahdavi
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Mohamad Reza
authors: MR
authors: Fadavi
authors: Prevention of Psychosocial Injuries, Research Centre, Ilam, IR Iran.
authors: Kourosh
authors: K
authors: Sayehmiri
authors: Clinical Microbiology Research Center, Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Nourkhoda
authors: N
authors: Sadeghifard
keywords: P. aeruginosa; Quorum sensing; Toxin-antitoxin systems