title: Association between toxin-antitoxin systems and biofilm formation.
abstract: BACKGROUND
  Toxin-antitoxin (TA) systems are found on the chromosomes and plasmids of many Bacteria such as Escherichia coli. The roles of TA systems in bacteria are enigmatic. Multiple biological functions of TA systems are proposed including growth modulation, persistence, and biofilm formation. Bioﬁlms of E. coli are cause of urinary tract infections, as well as bacteraemia.
  
  
  OBJECTIVE
  The current study aimed to find the association between biofilm formation and toxin-antitoxin systems in clinical isolates of E. coli.
  
  
  METHODS
  A total of 150 E. coli isolates were evaluated for biofilm formation by Congo red agar medium (CRA) and microtiter plate assay and the presence of different TA systems including MazEF, RelBE, hipBA, ccdAB and MqsRA.
  
  
  RESULTS
  The results of the analysis revealed that 107 E. coli isolates were potent for biofilm formation by CRA. The findings by microtiter plates showed that 102 E. coli isolates were biofilm producers. The results indicated that 80%, 85%, 70%, 91% and 82% of the isolates possessed MazEF, RelBE, hipBA, ccdAB and MqsRA TA loci, respectively.
  
  
  CONCLUSIONS
  The analysis recommended that TA genes are prevalent in clinical isolates of E. coli strains. The analysis revealed that hipBA TA system is associated with biofilm formation.
authors: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Sajedeh
authors: S
authors: Karimi
authors: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Sobhan
authors: S
authors: Ghafourian
authors: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Morovat
authors: M
authors: Taheri Kalani
authors: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Farid
authors: F
authors: Azizi Jalilian
authors: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Saeed
authors: S
authors: Hemati
authors: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, IR Iran.
authors: Nourkhoda
authors: N
authors: Sadeghifard
keywords: Biofilm; Escherichia coli; Toxin-Antitoxin Systems