Biofilm forming ability and production of curli and cellulose in clinical isolates of Enterobacteriaceae

In this study, 22 clinical isolates of Enterobacteriaceae including Citrobacterfreundii (6 strains), Enterobacter cloacae (5 strains), Enterobacter aerogenes (3 strains), Serratia marcescens (7 strains) and Pantoea spp. (1 strain) were investigated for the biofilm forming ability and biosynthesis of curli and cellulose. Biofilm forming ability was the highest among the isolates of E. cloacae and the lowest among the isolates of E. aerogenes. The expression of the biofilm-forming extracellular matrix components, cellulose and curli fimbriae, was examined by Congo-red (CR) staining and calcofluor staining methods. PCR screening for the presence of curli gene (csgA) revealed that 4 strains of E. cloacae and 1 strain of C. freundii carried the csgA, showing a good correlation between the phenotypic detection of curli fimbriae by CR staining method and the genotypic detection of curli gene by PCR in E. cloacae.