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Shivaji Sisinthy, Ranjit Konduri, Arunasri Kotakonda, Reddy Satyanaryana Gundlapally, Savitri Sharma; Global gene expression in ocular isolates of Escherichia coli with potential to form biofilm. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2346.
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© ARVO (1962-2015); The Authors (2016-present)
To establish the biofilm potential of ocular isolates of E.coli, to ascertain their antibiotic susceptibility and to identify genes that are responsible for biofilm formation and drug resistance.
Biofilm formation was assessed in 12 ocular isolates of E. coli using the congo red agar method and tissue culture plate method. The minimum inhibitory concentration (MIC) of eight antibiotics was determined against E. coli strain L-1216 in the biofilm and planktonic phases. To identify genes that may be differentially regulated during biofilm formation, ocular E. coli was allowed to form biofilm for 72 h and then used as the source for mRNA, cDNA preparation and DNA microarray. Ocular E. coli (L-1339) which did not form a biofilm was used as a control. All experiments were repeated thrice. Only genes that deviated from the control by more than 2 fold and with a p value <0.05 were considered as significantly differentially expressed.
Six of the 12 ocular isolates were biofilm positive. E. coli L-1216 was the best biofilm forming isolate. The MIC of all antibiotics in the biofilm state was >5mg and ≤0.032mg in the planktonic phase. DNA microarray data indicated that in the biofilm forming E. coli 426 and 866 genes were up and down regulated respectively compared to the non-biofilm forming cells. The heat map and the Principal Component Analysis also showed that the biofilm cells were more related to one other and were different from the non-biofilm cells. The differentially expressed genes in the biofilm forming cells could be classified as those involved in metabolic processes, in organization of cellular components and in cellular activities. In each of these categories, genes relevant to biofilm formation were present like genes coding for EPS synthesis, genes that facilitate adhesion, genes that respond to environmental signals and those that are related to drug resistance.
Ocular E. coli have the potential to form biofilm and cells in the biofilm are more resistant to antimicrobials. Several virulent genes like those coding for pili/fimbriae, lipopolysacccharides and exopolysaccharides synthesis, efflux pumps, environmental signals etc. are upregulated. This is the first study on DNA microarray analysis of an ocular E. coli with a potential to form biofilm.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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