Biofilm formation on borosilicate glass and polystyrene abiotic surfaces. (A) Qualitative assay showing that EC121 strain adhered to glass coverslips after 24 h of incubation at 37 °C, in DMEM. EAEC prototype strain 042 and E. coli HB101 were used as positive and negative controls, respectively. Bacteria were stained with crystal violet, observed by optical microscopy (OM) 400×. (B) Quantitative biofilm assays were performed in Dulbecco′s Modified Eagle′s Medium (DMEM) and tryptic soy broth (TSB), at 37 °C, for 24 h, comparing the capacity of strain EC121 to produce biofilm in polystyrene surface. EAEC 042 was used as a positive control, UPEC prototype strain CFT073 was used as an ExPEC control, and Laboratory strain HB101 was used as a negative control. p values: ** < 0.01; *** < 0.001; ns > 0.05.