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Shiga toxin-producing Escherichia coli (STEC) are recognized as being responsible for many cases of foodborne diseases worldwide. Cattle are the main reservoir of STEC, shedding the microorganisms in their feces. The serogroup STEC O91 has been associated with hemorrhagic colitis and hemolytic uremic syndrome. Locus of Adhesion and Autoaggregation (LAA) and its hes gene are related to the pathogenicity of STEC and the ability to form biofilms. Considering the frequent isolation of STEC O91, the biofilm-forming ability, and the possible role of hes in the pathogenicity of STEC, we propose to evaluate the ability of STEC to form biofilms and to evaluate the expression of hes before and after of biofilm formation. All strains were classified as strong biofilm-forming. The hes expression showed variability between strains before and after biofilm formation, and this may be due to other genes carried by each strain. This study is the first to report the relationship between biofilm formation, and hes expression and proposes that the analysis and diagnosis of LAA, especially hes as STEC O91 virulence factors, could elucidate these unknown mechanisms. Considering that there is no specific treatment for HUS, only supportive care, it is necessary to know the survival and virulence mechanisms of STEC O91. [ABSTRACT FROM AUTHOR]

Shiga toxin-producing Escherichia coli (STEC) are zoonotic food pathogens associated with foodborne diarrheal illness, hemorrhagic colitis, and complications such as hemolytic uremic syndrome (HUS). The ability to adhere to epithelial cells is an important virulence trait, and pathogenicity islands (PAIs) play an important role on it. Some STEC carrying a PAI named locus of enterocyte effacement (LEE-positive) have been frequently associated to HUS; however, STEC that do not carry LEE (LEE-negative) have also been associated with this outcome. The burden of disease caused by LEE-negative STEC has increased recently in several countries like Argentina, Chile, and Paraguay. A new PAI –the Locus of Adhesion and Autoagregation (LAA)—has been associated to severe disease in humans. In this study, we aimed to analyze the distribution of LAA and its possible predictor, the gene hes, in LEE-negative STEC strains isolated from Chile and Paraguay from different sources. The presence of the different LAA modules and hes were detected by PCR. LAA was found in 41.6% and 41.0% of strains isolated from Chile and Paraguay, respectively. Strains were isolated from diverse origins and belonged to several serogroups including O91, O103, and O113. The hes gene was detected in 50% of the isolates from Paraguay and Chile. Therefore, the detection of LAA and hes in STEC could complement current genetic evaluation schemes, allowing to classify LEE negative STEC strains as LAA-positive or LAA-negative STEC strains. [ABSTRACT FROM AUTHOR]

Adherent-invasive Escherichia coli (AIEC) have been extensively implicated in Crohn's disease pathogenesis. Currently, AIEC is identified phenotypically, since no molecular marker specific for AIEC exists. An algorithm based on single nucleotide polymorphisms was previously presented as a potential molecular tool to classify AIEC/non-AIEC, with 84% accuracy on a collection of 50 strains isolated in Girona (Spain). Herein, our aim was to determine the accuracy of the tool using AIEC/non-AIEC isolates from different geographical origins and extraintestinal pathogenic E. coli (ExPEC) strains. The accuracy of the tool was significantly reduced (61%) when external AIEC/non-AIEC strains from France, Chile, Mallorca (Spain) and Australia (82 AIEC, 57 non-AIEC and 45 ExPEC strains in total) were included. However, the inclusion of only the ExPEC strains showed that the tool was fairly accurate at differentiating these two close pathotypes (84.6% sensitivity; 79% accuracy). Moreover, the accuracy was still high (81%) for those AIEC/non-AIEC strains isolated from Girona and Mallorca (N = 63); two collections obtained from independent studies but geographically close. Our findings indicate that the presented tool is not universal since it would be only applicable for strains from similar geographic origin and demonstrates the need to include strains from different origins to validate such tools. [ABSTRACT FROM AUTHOR]

Shiga toxin-producing Escherichia coli (STEC) cause diarrhea and dysentery, which may progress to hemolytic uremic syndrome (HUS). Vaccination has been proposed as a preventive approach against STEC infection; however, there is no vaccine for humans and those used in animals reduce but do not eliminate the intestinal colonization of STEC. The OmpT, Cah and Hes proteins are widely distributed among clinical STEC strains and are recognized by serum IgG and IgA in patients with HUS. Here, we develop a vaccine formulation based on two chimeric antigens containing epitopes of OmpT, Cah and Hes proteins against STEC strains. Intramuscular and intranasal immunization of mice with these chimeric antigens elicited systemic and local long-lasting humoral responses. However, the class of antibodies generated was dependent on the adjuvant and the route of administration. Moreover, while intramuscular immunization with the combination of the chimeric antigens conferred protection against colonization by STEC O157:H7, the intranasal conferred protection against renal damage caused by STEC O91:H21. This preclinical study supports the potential use of this formulation based on recombinant chimeric proteins as a preventive strategy against STEC infections. [ABSTRACT FROM AUTHOR]

A model of the homogeneous chemistry and transport processes within the separator of a chrome-alum electrowinning cell is introduced, discussed, and compared to experiment. The influences of diffusion, electromigration, and convection are included; it is found that convection was the dominant mode of transport for the experimental conditions. Simulation results explain experimental observations concerning an apparent disappearance of dichromate ions produced at the cell anode. The relation between potential drop across the diaphragm and the current and fluid flow is also illustrated. The model is used to recommend future experimental and theoretical work. [ABSTRACT FROM AUTHOR]