Production of cellulose and curli fimbria by shiga toxin-producing Escherichia coli isolated from recreational waters

MARUCCI, PATRICIA LILIANA; BRUGNONI, LORENA INÉS; SICA, MARÍA GABRIELA; CUBITTO, MARÍA AMELIA

San Miguel de Tucumán

Congreso; VII Congreso Argentino de Microbiología General; 2011

Sociedad Argentina de Microbiología General

The high persistence of Shiga toxing-producing Escherichia coli (STEC) cells in soils and water appears to be an important risk factor for contamination and has been increasingly studied during the last years. Cells of E. coli may need to live for a considerable length of time during their life cycle outside animal hosts where the conditions may be less than optimal. Association with solid surfaces in an aqueous environment is a strategy that cells use to survive under suboptimal conditions. E. coli O157 and other pathogens can form biofilms when they are in nutritionally deficient media (water, soil and inert surfaces). In members of the Family Enterobacteriaceae, biofilm formation is associated with the expression of curli and exopolysaccharide (EPS), such as cellulose. In this Family, the co-expression of thin aggregative fimbriae and cellulose leads to an aggregative colony phenotype (red, dry, and rough [rdar]) when grown on medium containing the dye Congo red. The rdar morphotype produces an extracellular matrix consisting of cellulose and curli fimbriae, which is the major determinant of cell-cell interactions and cell adherence to hydrophilic and hydrophobic abiotic surfaces. The aim of this study was to recognize the capacity to express the curli and cellulose operon in four STEC non-O157, isolated from recreational waters in the region of Sierra de la Ventana (Buenos Aires Province, Argentina). These strains amplified the stx2 gene and two of these carried the eae factor. The isolations were made onto McConkey agar. After incubation overnight at 37ºC, colonies were streaked onto Luria–Bertani (LB) agar plates without salt supplemented with Congo red. The plates were either incubated for 72 h at 28 ºC. All STEC strains showed the morphotype rdar: red colony, expresses curli fimbriae and cellulose on LB agar without salt, which is coupled to the biofilm-formation capability of the organism. The rdar morphotype has been linked to increased virulence. This work suggests the presence E. coli non-O157 with virulent characteristics in rivers and streams which are used for recreational purposes in Buenos Aires Province.