Determination of adhesin gene sequences in, and biofilm formation by, O157 and non-O157 Shiga toxin-producing Escherichia coli strains isolated from different sources.

Biofilm formation by Shiga toxin-producing Escherichia coli (STEC) has been associated with the expression of different adhesins (type 1 fimbria, curli, Ag43, Cah, and EhaA). In this study, biofilm formation and the presence of adhesin-related gene sequences were determined by PCR in 18 O157 strains and 33 non-O157 strains isolated from different sources (human, animal, food, and water). The expression of different adhesins was also assessed by reverse transcription-PCR (RT-PCR), Congo red agar plates, and mannose-sensitive hemagglutination (MSHA) assay. Biofilm formation occurred in 5/18 (28%) O157 STEC strains and 17/33 (51%) non-O157 STEC strains from different serotypes and sources, when the assays were performed at 28°C for 48 h. Among the non-O157 biofilm-producing isolates, 12/17 (71%) expressed type 1 fimbriae and 11/17 (65%) expressed curli and produced cellulose, while 8/17 (47%) were considered to be Ag43(+) by RT-PCR. Among O157 strains, a close correlation was observed between biofilm formation and expression of curli and cellulose. In non-O157 strains, it seems that, in addition to the presence of curli, the ability to form biofilm is associated with the presence of other factors such as type 1 fimbriae and autotransporter proteins, which may contribute to the persistence of these organisms in the environment.

Biofilm formation, invasiveness and colicinogeny in locus of enterocyte and effacement negative O113:H21 Shigatoxigenic Escherichia coli

AimsAlthough Shiga toxins (Stx) are well-established virulence traits of O113:H21 Shigatoxigenic Escherichia coli (STEC) strains, a shortage in the knowledge of other virulence properties that may contribute to pathogenesis may exist in this serotype. This study investigated biofilm, invasiveness and colicinogeny capabilities in O113:H21 STEC isolated in Brazil, mostly from animal reservoirs. A search for genes that were reported to participate in the process of biofilm formation was also performed. Methods and ResultsThe 34 O113:H21 STEC isolates analysed were assayed for biofilm production in polystyrene microplates. Genes for biofilm were investigated by PCR. Invasion of cell lineages was assessed in gentamicin protection assays and colicinogeny was investigated by phenotypic tests. Fifty per cent of the strains were biofilm formers, and 35% exhibited an invasive behaviour. The pattern of distribution of biofilm-related genes did not correlate with biofilm phenotypes observed, and a high percentage of the investigated strains were able to secrete colicins. ConclusionAbility to form biofilm, invasiveness and colicinogeny is demonstrated for the first time in a collection of O113:H21 STEC. Significance and Impact of the StudyThe ability to express three additional phenotypes besides Stx production may be a factor influencing the pathogenicity and persistence potential of O113:H21 STEC.

Determination of Adhesin Gene Sequences in, and Biofilm Formationby, O157 and Non-O157 Shiga Toxin-Producing Escherichia coli Strains Isolated from Different Sources

Biofilm formation by Shiga toxin-producing Escherichia coli (STEC) has been associated with the expressionof different adhesins (type 1 fimbria, curli, Ag43, Cah, and EhaA). In this study, biofilm formation and thepresence of adhesin-related gene sequences were determined by PCR in 18 O157 strains and 33 non-O157strains isolated from different sources (human, animal, food, and water). The expression of different adhesinswas also assessed by reverse transcription-PCR (RT-PCR), Congo red agar plates, and mannose-sensitivehemagglutination (MSHA) assay. Biofilm formation occurred in 5/18 (28%) O157 STEC strains and 17/33(51%) non-O157 STEC strains from different serotypes and sources, when the assays were performed at 28°Cfor 48 h. Among the non-O157 biofilm-producing isolates, 12/17 (71%) expressed type 1 fimbriae and 11/17(65%) expressed curli and produced cellulose, while 8/17 (47%) were considered to be Ag43 by RT-PCR.Among O157 strains, a close correlation was observed between biofilm formation and expression of curli andcellulose. In non-O157 strains, it seems that, in addition to the presence of curli, the ability to form biofilm isassociated with the presence of other factors such as type 1 fimbriae and autotransporter proteins, which maycontribute to the persistence of these organisms in the environment.