BIOFILM FORMATION BY NON PATHOGENIC ESCHERICHIA COLI AND IN DIVERSE PATOTYPES OF DIARRHEAGENIC E. COLI STRAINS.

AC03

Cristiane Moda Mota, Hebert Fabrício Culler, Marcia Regina Franzolin.

Laboratório de Bacteriologia, Instituto Butantan, SP, Brasil

The infectious diarrhea is considered a major cause of infant mortality. Microorganisms belonging to the family Enterobacteriaceae are the main cause of intestinal infection, mainly Escherichia coli. Biofilms have been described as sessile bacterial communities that live attached to each other and to surfaces. It plays mechanisms of colonization, confering bacterial resistance to the action of antibiotics and is also recognized as the source of persistent infection. The biofilm formation has been described in the E. coli strains that show the pattern of aggregative adherence (EAEC), as well as in strains of Shiga-toxin-producing E. coli (STEC), Enterotoxigenic E. coli (ETEC), Diffuse-adhering E. coli (DAEC), Enteropathogenic E. coli (EPEC), and in commensal E. coli K-12. The understanding of biofilm formation is essential to know their role in pathogenesis, enabling the development of alternative therapies. The aim of this study was to verify the capacity of biofilm formation by non pathogenic Escherichia coli and diarrheagenic Escherichia coli strains (Enteroaggregative E. coli, typical and atypical Enteropathogenic E. coli, Enterotoxigenic E. coli, Shiga-toxin-producing E. coli, Enterohemorrhagic E. coli and Diffuse-adhering E. coli), in abiotic surfaces (polystyrene) and cellular surfaces. We analyzed the biofilm formation in 95 E. col: 20 non pathogenic Escherichia coli strains and 75 diarrheagenic E. coli strains (ETEC, EAEC, aEPEC, tEPEC, DAEC, STEC and EHEC), isolated from children living in Salvador, Bahia. The strains were screened for biofilm production using colorimetric assay of violet crystal using polystyrene 24-well culture dishes and was quantified using enzyme immunosorbent assay plate reader in length of wave of 595 nm. The strains had been capable to form biofilm in polystyrene, regardless of their pathotypes. While 56.8% of the strains showed low biofilm formation (OD = 0 – 0.043), 36.9% of the strains showed intermediate formation (OD = 0.044 – 1.281) and only 6.3% had high capacity for biofilm formation (OD > 1.282). The DAEC, tEPEC, aEPEC, ETEC and EHEC strains showed low to intermediary capacity of biofilm formation, in comparison with the EAEC strains. All E. coli pathotypes and non pathogenic E. coli presented strains capable of produce biofilms, as described in the literature. The colorimetric assay of violet crystal, a presumptive test used to select the samples better-producing biofilms, showed the high potentiality of the EAEC strains to produce biofilm in regard with other pathotypes and non pathogenic E. coli. This capacity can be explained by its aggregative adherence pattern, which is associated with fimbrial adhesins and it is known that the adhesion is the initial process to biofilm development. The samples that showed a higher rate of biofilm formation will be submitted to the methodology of direct counting of CFU/cm² attached to the biofilm after breaking with Triton X-100, and to the interaction with HeLa cells assays.