Shiga toxin-producing Escherichia coli O157: H7 shows an increased pathogenicity in mice after the passage through the gastrointestinal tract of the same host

Haemolytic uraemic syndrome (HUS) is a rare but life-threatening complication of Shiga toxin (Stx)-producing Escherichia coli (STEC) infections, characterized by acute renal failure, thrombocytopenia and haemolytic anaemia. Although the main infection route is the consumption of contaminated food or water, person-to-person transmission has been suggested in several situations. Moreover, epidemiological data indicate that the horizontal transmission of several pathogens, including STEC, among individuals of the same species requires significantly lower doses than those used in animal models infected with laboratory-cultured bacteria. Thus, the aim of this study was to evaluate whether the passage of a clinically isolated STEC strain through the gastrointestinal tract of mice affects its pathogenicity in mice. To test this, weaned mice were orally inoculated by gavage with either an E. coli O157: H7 isolate from an HUS patient, or the same strain recovered from stools after one or two successive passages through the gastrointestinal tract of the mice. We show that stool-recovered strains are able to induce a more generalized and persistent colonization than the parent strain. Furthermore, a 10 4-fold-reduced inoculum of the stool-recovered strains still causes gut colonization and mouse mortality, which are not observed with the parent strain. These results indicate an increased pathogenicity in stool-recovered strains that may be associated with an increased ability to colonize the mouse intestine.Fil: Fernández Brando, Romina Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Miliwebsky, Elizabeth. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; Argentina. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Mejias, María Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Baschkier, Ariela. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; Argentina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; ArgentinaFil: Panek, Cecilia Analía. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Abrey Recalde, Maria Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Cabrera, Gabriel Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Ramos, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Rivas, Marta. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; Argentina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud “Dr. C. G. Malbrán”; ArgentinaFil: Palermo, Marina Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentin

Development and evaluation of a novel VHH-based immunocapture assay for high-sensitivity detection of Shiga toxin type 2 (Stx2) in stool samples

Shiga toxin (Stx)-producing Escherichia coli (STEC) is the main cause of postdiarrheal hemolytic-uremic syndrome (HUS), a life-threatening clinical complication characterized by hemolytic anemia, thrombocytopenia, and acute renal failure that mainly affects children. A relevant feature of STEC strains is the production of Stx, and all of them express Stx1 and/or Stx2 regardless of the strain serotype. Therefore, Stx detection assays are considered the most suitable methods for the early detection of STEC infections. Single-domain antibodies from camelids (VHHs) exhibit several advantages in comparison with conventional antibodies, making them promising tools for diagnosis. In this work, we have exploited VHH technology for the development of an immunocapture assay for Stx2 detection. Thirteen anti- Stx2 VHHs previously obtained from a variable-domain repertoire library were selected and evaluated in 130 capture-detection pair combinations for Stx detection. Based on this analysis, two VHHs were selected and a double VHH-based biotinstreptavidin capture enzyme-linked immunosorbent assay (ELISA) with spectrophotometric detection was developed and optimized for Stx2 detection. This assay showed an excellent analytical and clinical sensitivity in both STEC culture supernatants and stool samples even higher than the sensitivity of a commercial ELISA. Furthermore, based on the analysis of stool samples, the VHH-based ELISA showed high correlation with stx2 detection by PCR and a commercial rapid membrane-based immunoassay. The intrinsic properties of VHHs (high target affinity and specificity, stability, and ease of expression at high yields in recombinant bacteria) and their optimal performance for Stx detection make them attractive tools for the diagnosis of HUS related to STEC (STEC-HUS).Fil: Melli, Luciano Jorge. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Zylberman, Vanesa. Inmunova; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hiriart, Yanina. Inmunova; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lauche, Constanza E.. Inmunova; ArgentinaFil: Baschkier, Ariela. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Pardo, Romina. Inmunova; ArgentinaFil: Miliwebsky, Elizabeth. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Chinen, Isabel. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Rivas, Marta. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Goldbaum, Fernando A.. Inmunova; ArgentinaFil: Ugalde, Juan Esteban. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Comerci, Diego José. Inmunova; Argentina. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Ciocchini, Andres Eduardo. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Biotecnológicas; Argentin

Hemorragia y oclusión intestinal asociadas a escherichia coli O127:H21 productor de toxina shiga

We report a case of a nine-year old boy with vomiting, abdominal pain and fever, who underwent surgery with a diagnosis of appendicitis in Mendoza and from whom a Shiga toxin-producing Escherichia coli (STEC) O127:H21 strain was recovered. Forty-eight hours after surgery he presented bilious vomiting and two episodes of intestinal bleeding. Laboratory findings included: hematocrit, 35%; blood urea nitrogen, 0.22 g/L. The urinary output was normal. The following day physical examination showed an alert mildly hydrated child, without fever but with distended and painful abdomen. The patient was again submitted to surgery with a diagnosis of intestinal occlusion. Bleeding and multiple adhesions in jejunum and ileum were found. The patient still had tense and painful abdomen and presented two bowel movements with blood; hematocrit fell to 29% and blood urea nitrogen rose to 0.32 g/L. STEC O127:H21 eae(-)/Stx2/Stx2vh-b(+)/E-Hly(+) was isolated from a stool sample. He was discharged after 10 days of hospitalization and no long-term complications such as HUS or TTP were observed. This is the first report, to our knowledge, on the isolation of E. coli O127:H21, carrying the virulence factors that characterize STEC strains, associated to an enterohemorrhagic colitis case. This serotype was previously characterized as a non-classic enteropathogenic E. coli (EPEC). STEC infections can mimic infectious or noninfectious pathologies. Therefore an important aspect of clinical management is making the diagnosis using different criteria thereby avoiding misdiagnoses which have occasionally led to invasive diagnostic and therapeutic procedures or the inappropriate use of antibiotics.Se presenta el caso de un niño de 9 años, eutrófico, perteneciente a una familia de bajo nivel socioeconómico en Mendoza, que ingresó al hospital con vómitos, fiebre y dolor abdominal y al cual se le practicó apendectomía, aislándose Escherichia coli O127:H21, productor de toxina Shiga (STEC) en el coprocultivo. A las 48 horas post-cirugía, el paciente presentó vómitos biliosos y dos episodios de hemorragia intestinal. El hematocrito fue de 35% y la uremia de 0.22 g/L. La diuresis fue normal. Al día siguiente estaba afebril, alerta, hidratado, pero con el abdomen distendido y doloroso. Fue enviado nuevamente a cirugía con diagnóstico de oclusión intestinal, observándose durante la misma, sangrado intestinal y múltiples adherencias en yeyuno e íleo, que fueron manualmente removidas. El paciente continuó con distensión abdominal y presentó dos deposiciones sanguinolentas, el hematocrito disminuyó a 29% y la urea en sangre se elevó a 0.32 g/L. STEC O127:H21 eae(-)/Stx2/Stx2vh-b(+)/ E-Hly(+) fue aislado de la materia fecal. El niño fue dado de alta después de 10 días de hospitalización sin presentar complicaciones como SUH o PTT. Esta es la primera comunicación sobre el aislamiento de E. coli O127:H21 de un caso de enterocolitis hemorrágica, con los factores de virulencia que caracterizan a STEC. Este serotipo era reconocido como perteneciente a la categoría de E. coli enteropatógeno no clásico. Teniendo en cuenta que las infecciones por STEC pueden mimetizar otras patologías infecciosas o no infecciosas, es importante utilizar distintos criterios diagnósticos, para evitar prácticas médicas o tratamientos innecesarios.Fil: Rivas, Marta. ANLIS Dr.C.G.Malbrán, Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Miliwebsky, Elizabeth. ANLIS Dr.C.G.Malbrán, Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Balbi, Laura. Hospital Pediátrico Dr. Humberto Notti; Argentina.Fil: García, Beatriz. Hospital Pediátrico Dr. Humberto Notti; Argentina.Fil: Leardini, Nelida. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Microbiología; Argentina.Fil: Tous, Monica. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Microbiología; Argentina.Fil: Chillemi, German. ANLIS Dr.C.G.Malbrán, Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Baschkier, Ariela. ANLIS Dr.C.G.Malbrán, Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Strugo, Liliana. Hospital Pediátrico Dr. Humberto Notti; Argentina

Hemorragia y oclusión intestinal asociadas a escherichia coli O127:H21 productor de toxina shiga

We report a case of a nine-year old boy with vomiting, abdominal pain and fever, who underwent surgery with a diagnosis of appendicitis in Mendoza and from whom a Shiga toxin-producing Escherichia coli (STEC) O127:H21 strain was recovered. Forty-eight hours after surgery he presented bilious vomiting and two episodes of intestinal bleeding. Laboratory findings included: hematocrit, 35%; blood urea nitrogen, 0.22 g/L. The urinary output was normal. The following day physical examination showed an alert mildly hydrated child, without fever but with distended and painful abdomen. The patient was again submitted to surgery with a diagnosis of intestinal occlusion. Bleeding and multiple adhesions in jejunum and ileum were found. The patient still had tense and painful abdomen and presented two bowel movements with blood; hematocrit fell to 29% and blood urea nitrogen rose to 0.32 g/L. STEC O127:H21 eae(-)/Stx2/Stx2vh-b(+)/E-Hly(+) was isolated from a stool sample. He was discharged after 10 days of hospitalization and no long-term complications such as HUS or TTP were observed. This is the first report, to our knowledge, on the isolation of E. coli O127:H21, carrying the virulence factors that characterize STEC strains, associated to an enterohemorrhagic colitis case. This serotype was previously characterized as a non-classic enteropathogenic E. coli (EPEC). STEC infections can mimic infectious or noninfectious pathologies. Therefore an important aspect of clinical management is making the diagnosis using different criteria thereby avoiding misdiagnoses which have occasionally led to invasive diagnostic and therapeutic procedures or the inappropriate use of antibiotics.Se presenta el caso de un niño de 9 años, eutrófico, perteneciente a una familia de bajo nivel socioeconómico en Mendoza, que ingresó al hospital con vómitos, fiebre y dolor abdominal y al cual se le practicó apendectomía, aislándose Escherichia coli O127:H21, productor de toxina Shiga (STEC) en el coprocultivo. A las 48 horas post-cirugía, el paciente presentó vómitos biliosos y dos episodios de hemorragia intestinal. El hematocrito fue de 35% y la uremia de 0.22 g/L. La diuresis fue normal. Al día siguiente estaba afebril, alerta, hidratado, pero con el abdomen distendido y doloroso. Fue enviado nuevamente a cirugía con diagnóstico de oclusión intestinal, observándose durante la misma, sangrado intestinal y múltiples adherencias en yeyuno e íleo, que fueron manualmente removidas. El paciente continuó con distensión abdominal y presentó dos deposiciones sanguinolentas, el hematocrito disminuyó a 29% y la urea en sangre se elevó a 0.32 g/L. STEC O127:H21 eae(-)/Stx2/Stx2vh-b(+)/ E-Hly(+) fue aislado de la materia fecal. El niño fue dado de alta después de 10 días de hospitalización sin presentar complicaciones como SUH o PTT. Esta es la primera comunicación sobre el aislamiento de E. coli O127:H21 de un caso de enterocolitis hemorrágica, con los factores de virulencia que caracterizan a STEC. Este serotipo era reconocido como perteneciente a la categoría de E. coli enteropatógeno no clásico. Teniendo en cuenta que las infecciones por STEC pueden mimetizar otras patologías infecciosas o no infecciosas, es importante utilizar distintos criterios diagnósticos, para evitar prácticas médicas o tratamientos innecesarios.Fil: Rivas, Marta. ANLIS Dr.C.G.Malbrán, Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Miliwebsky, Elizabeth. ANLIS Dr.C.G.Malbrán, Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Balbi, Laura. Hospital Pediátrico Dr. Humberto Notti; Argentina.Fil: García, Beatriz. Hospital Pediátrico Dr. Humberto Notti; Argentina.Fil: Leardini, Nelida. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Microbiología; Argentina.Fil: Tous, Monica. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Microbiología; Argentina.Fil: Chillemi, German. ANLIS Dr.C.G.Malbrán, Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Baschkier, Ariela. ANLIS Dr.C.G.Malbrán, Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Strugo, Liliana. Hospital Pediátrico Dr. Humberto Notti; Argentina

Immunization with a chimera between the B subunit of Shiga toxin type 2 and Brucella Lumazine Synthase confers total protection against Shiga toxins in mice

The striking feature of Enterohemorrhagic Escherichia coli (EHEC) infections is the production of Shiga toxins (Stx) implicated in the development of the life-threatening hemolytic uremic syndrome (HUS). Despite the magnitude of the social impact of EHEC infections, no licensed vaccine or effective therapy is presently available for human use. One of the biggest challenges is to develop an effective and safe immunogen to ensure non toxicity but also a strong input to the immune system to induce long-lasting, high affinity antibodies with anti-Stx neutralizing capacity. The enzyme lumazine synthase from Brucella spp. (BLS) is a highly stable dimer of pentamers and a scaffold with enormous plasticity for displaying foreign antigens on it. Taking into account BLS advantages and the potential capacity of the B subunit of Stx2 (Stx2B) to induce antibodies that prevent Stx2 toxicity by blocking its entrance to the host cells, we engineered a new immunogen inserting Stx2B at the amino termini of BLS. The resulting chimera demonstrated a strong capacity to induce long-lasting humoral immune response in mice. The chimera induced antibodies with high neutralizing capacity for Stx2 and its variants. Moreover, immunized mice were completely protected against i.v. Stx2-challenge and weaned mice receiving an oral challenge with EHEC were completely protected by the transference of immune sera. We conclude that this novel immunogen represents a promising candidate for vaccine or antibody development with preventive or therapeutic ends, for use in HUS endemic areas or during future outbreaks caused by pathogenic strains of Stx-producing E. coli.Fil: Mejias, María Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Ghersi, Giselle. Inmunova S.A; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Craig, Patricio Oliver. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Panek, Cecilia Analía. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Bentancor, Leticia Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Baschkier, Ariela. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud; ArgentinaFil: Goldbaum, Fernando Alberto. Inmunova S.A; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Zylberman, Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina. Inmunova S.A; ArgentinaFil: Palermo, Marina Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentin

Immunization with a Chimera Consisting of the B Subunit of Shiga Toxin Type 2 and Brucella Lumazine Synthase Confers Total Protection against Shiga Toxins in Mice.

The striking feature of enterohemorrhagic Escherichia coli (EHEC) infections is the production of Shiga toxins (Stx) implicated in the development of the life-threatening hemolytic uremic syndrome. Despite the magnitude of the social impact of EHEC infections, no licensed vaccine or effective therapy is available for human use. One of the biggest challenges is to develop an effective and safe immunogen to ensure nontoxicity, as well as a strong input to the immune system to induce long-lasting, high-affinity Abs with anti-Stx–neutralizing capacity. The enzyme lumazine synthase from Brucella spp. (BLS) is a highly stable dimer of pentamers and a scaffold with enormous plasticity on which to display foreign Ags. Taking into account the advantages of BLS and the potential capacity of the B subunit of Stx2 to induce Abs that prevent Stx2 toxicity by blocking its entrance into the host cells, we engineered a new immunogen by inserting the B subunit of Stx2 at the amino termini of BLS. The resulting chimera demonstrated a strong capacity to induce a long-lasting humoral immune response in mice. The chimera induced Abs with high neutralizing capacity for Stx2 and its variants. Moreover, immunized mice were completely protected against i.v. Stx2 challenge, and weaned mice receiving an oral challenge with EHEC were completely protected by the transference of immune sera. We conclude that this novel immunogen represents a promising candidate for vaccine or Ab development with preventive or therapeutic ends, for use in hemolytic uremic syndrome–endemic areas or during future outbreaks caused by pathogenic strains of Stx-producing E. coli.Fil: Mejias, Maria Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental; ArgentinaFil: Ghersi, Giselle. Inmunova S.a; ArgentinaFil: Craig, Patricio Oliver. Fundación Instituto Leloir; ArgentinaFil: Panek, Cecilia Analia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental; ArgentinaFil: Bentancor, Leticia Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental; ArgentinaFil: Baschkier, Ariela. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Goldbaum, Fernando Alberto. Inmunova S.a; Argentina. Fundación Instituto Leloir; ArgentinaFil: Zylberman, Vanesa. Inmunova S.a; Argentina. Fundación Instituto Leloir; ArgentinaFil: Palermo, Marina Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental; Argentin

Shiga toxin-producing Escherichia coli O157 in beef and chicken burgers, and chicken carcasses in Buenos Aires, Argentina

Fil: Chinen, Isabel. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología. Servicio Fisiopatogenia; Argentina.Fil: Epszteyn, Sergio. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología. Servicio Fisiopatogenia; Argentina.Fil: Melamed, Celia L. Departamento Laboratorio Investigación y Monitoreo, Dirección General de Higiene y Seguridad Alimentaria, Gobierno de la Ciudad de Buenos Aires, Patricias Argentinas 277, (1405) Buenos Aires; Argentina.Fil: Aguerre, Lorena. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología. Servicio Fisiopatogenia; Argentina.Fil: Martínez Espinosa, Estela. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología. Servicio Fisiopatogenia; Argentina.Fil: Motter, Mariana M. Departamento Laboratorio Investigación y Monitoreo, Dirección General de Higiene y Seguridad Alimentaria, Gobierno de la Ciudad de Buenos Aires, Patricias Argentinas 277, (1405) Buenos Aires; Argentina.Fil: Baschkier, Ariela. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología. Servicio Fisiopatogenia; Argentina.Fil: Manfredi, Eduardo. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología. Servicio Fisiopatogenia; Argentina.Fil: Miliwebsky, Elizabeth. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología. Servicio Fisiopatogenia; Argentina.Fil: Rivas, Marta. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriología. Servicio Fisiopatogenia; Argentina.We describe the isolation and characterization of Shiga toxin (Stx)-producing Escherichia coli (STEC) O157:H7 from cooked and uncooked beef and chicken burgers and from chicken carcasses collected during sampling procedures in 2001 and 2002 in Buenos Aires City, Argentina. Of the 24 STEC O157:H7 strains isolated, 20 were recovered from 19 (6.8%) out of 279 samples of beef and chicken burgers, and 4 strains from 4 (10.3%) out of 39 chicken carcasses. The samples were analyzed following the USDA/FSIS 2002 method. The prevalent stx genotype was stx(2) and stx(2c) (12 strains, 50%). All strains were characterized as eae and ehxA-positive. By XbaI-PFGE, the strains yielded 10 different patterns. Eighteen out of 24 strains were grouped in four clusters: #1 (4 strains, AREXHX01.0043), #2 (4 strains, AREXHX01.0022), #3 (8 strains, AREXHX01.0139), and #4 (2 strains, AREXHX01.0200). Identical strains by phage typing, stx genotyping and PFGE were detected in uncooked and cooked beef and chicken burgers in different restaurants, which had been collected on the same or different sampling dates. These findings help to underline the importance of STEC O157 detection in meat products, to improve active surveillance, and to define control strategies in order to prevent new cases of STEC infection

The Importance of Shiga Toxin-Producing <i>Escherichia coli</i> O145:NM[H28]/H28 Infections in Argentina, 1998–2020

Shiga toxin-producing Escherichia coli (STEC) is known as a pathogen associated with food-borne diseases. The STEC O145 serogroup has been related with acute watery diarrhea, bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). Argentina has the highest rate of HUS worldwide with 70% of the cases associated with STEC infections. We aimed to describe the epidemiology and genetic diversity of STEC O145 strains isolated across Argentina between 1998–2020. The strains isolated from 543 cases of human disease and four cattle, were pheno-genotipically characterized. Sequencing of five strains was performed. The strains were serotyped as O145:NM[H28]/H28, O145:H25, and O145:HNT, and mainly characterized as O145:NM[H28]/stx2a/eae/ehxA (98.1%). The results obtained by sequencing were consistent with those obtained by traditional methods and additional genes involved in different mechanisms of the pathogen were observed. In this study, we confirmed that STEC O145 strains are the second serogroup after O157 and represent 20.3% of HUS cases in Argentina. The frequency of STEC O145 and other significant serogroups is of utmost importance for public health in the country. This study encourages the improvement of the surveillance system to prevent severe cases of human disease

Retinoid levels influence enterohemorrhagic Escherichia coli infection and shiga toxin susceptibility in mice

Enterohemorrhagic Escherichia coli (EHEC) is a food-borne pathogen that produces Shiga toxin (Stx) and causes hemorrhagic colitis. Under some circumstances, Stx produced within the intestinal tract enters the bloodstream, leading to systemic complications that may cause the potentially fatal hemolytic-uremic syndrome. Although retinoids like vitamin A (VA) and retinoic acid (RA) are beneficial to gut integrity and the immune system, the effect of VA supplementation on gastrointestinal infections of different etiologies has been controversial. Thus, the aim of this work was to study the influence of different VA status on the outcome of an EHEC intestinal infection in mice. We report that VA deficiency worsened the intestinal damage during EHEC infection but simultaneously improved survival. Since death is associated mainly with Stx toxicity, Stx was intravenously inoculated to analyze whether retinoid levels affect Stx susceptibility. Interestingly, while VA-deficient (VA-D) mice were resistant to a lethal dose of Stx2, RA-supplemented mice were more susceptible to it. Given that peripheral blood polymorphonuclear cells (PMNs) are known to potentiate Stx2 toxicity, we studied the influence of retinoid levels on the absolute number and function of PMNs. We found that VA-D mice had decreased PMN numbers and a diminished capacity to produce reactive oxygen species, while RA supplementation had the opposite effect. These results are in line with the well-known function of retinoids in maintaining the homeostasis of the gut but support the idea that they have a proinflammatory effect by acting, in part, on the PMN population.Fil: Cabrera, Gabriel Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental; Argentina. Academia Nacional de Medicina de Buenos Aires; ArgentinaFil: Fernández Brando, Romina Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental; Argentina. Academia Nacional de Medicina de Buenos Aires; ArgentinaFil: Abrey Recalde, Maria Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental; Argentina. Academia Nacional de Medicina de Buenos Aires; ArgentinaFil: Baschkier, Ariela. Direccion Nacional de Instituto de Investigacion. Adm.nacional de Laboratorio E Instituto de Salud "dr.c.g.malbran". Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriologia; ArgentinaFil: Vasconcelos Esteves Pinto, Alipio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Laboratorio de Neurofisiología; ArgentinaFil: Goldstein Raij, Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas. Laboratorio de Neurofisiología; ArgentinaFil: Zotta, Elsa. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Ciencias Fisiológicas; ArgentinaFil: Meiss, Roberto. Academia Nacional de Medicina de Buenos Aires; ArgentinaFil: Rivas, Marta. Direccion Nacional de Instituto de Investigacion. Adm.nacional de Laboratorio E Instituto de Salud "dr.c.g.malbran". Instituto Nacional de Enfermedades Infecciosas. Departamento de Bacteriologia; ArgentinaFil: Palermo, Marina Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental; Argentina. Academia Nacional de Medicina de Buenos Aires; Argentin

Oral administration of Shiga toxin-producing Eschericcia coli induces intestinal and systemic specific immune response in mice

Hemolytic uremic syndrome (HUS) is the major complication of gastrointestinal infections with enterohemorrhagic Escherichia coli (EHEC) and is mediated by the production of Shiga toxins (Stx). Although it has been previously reported that not only HUS patients but healthy children have anti-Stx antibodies, very little is known about how these infections impact on mucosal immune system to generate a specific immune response. This work aimed to evaluate the immune responses elicited after a single oral dose of EHEC in a mouse model of HUS at weaning. We found sequential activation of T and B lymphocytes together with an increased percentage of IgA-bearing B cells in Peyer´s patches and mesenteric lymph nodes. We also found fecal anti-EHEC IgA and serum anti-Stx2 IgG in EHEC-inoculated mice. Besides, these mice were partially protected against an intravenous challenge with Stx2. These data demonstrate that one episode of EHEC infection is enough to induce activation in the gut-associated lymphoid tissue, especially the B cell compartment, and lead to the production of specific IgA in mucosal tissue and the generation of systemic protection against Stx2 in a percentage of intragastrically inoculated mice. These data also support the epidemiologic observation that a second episode of HUS is very rare.Fil: Fernández Brando, Romina Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Cabrera, Gabriel Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Baschkier, Ariela. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Mejias, María Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Panek, Cecilia Analía. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Miliwebsky, Elizabeth. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Abrey Recalde, Maria Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Bentancor, Leticia Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Ramos, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Rivas, Marta. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas; ArgentinaFil: Palermo, Marina Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentin