Escherichia coli productora de toxina Shiga: el desafío de adherirse para sobrevivir / Shiga toxin producing Escherichia coli: the challenge of adherence to survive

Resumen Las cepas de Escherichia coli productoras de toxina Shiga (STEC) son reconocidas como responsables de un alto número de casos de enfermedades de transmisión alimentaria a nivel mundial. Su patogenicidad ha sido vinculada directamente con la actividad de las toxinas (Stx); sin embargo, la habilidad de estas bacterias para colonizar al huésped y otras superficies puede ser esencial para desarrollar su poder patogénico. La gran plasticidad genómica de cepas STEC se infiere de la variabilidad de perfiles de virulencia, con la frecuente emergencia de cepas con nuevos genes, codificados en nuevas islas de patogenicidad vinculadas al metabolismo y la adherencia. La formación de biofilm es un mecanismo espontáneo por el cual las cepas STEC resisten en un ambiente hostil, lo que les permite sobrevivir y, de esa forma, llegar al huésped, a través de los alimentos o de las superficies que están en contacto con ellos. Este mecanismo presenta una alta variabilidad intra e interserotipo y su desarrollo no depende solo de los microorganismos que lo conforman. Factores inherentes al ambiente (pH, temperatura) y la superficie (acero inoxidable, poliestireno) a la que pueden adherirse influyen en la expresión de biofilm. El concepto «una salud¼ implica la interrelación entre los actores de salud pública, animal y ambiental para lograr alimentos inocuos y evitar contaminación cruzada y resistencia a sanitizantes, lo cual pone de manifiesto la necesidad de identificar patógenos emergentes a través de nuevos marcadores moleculares, que detecten cepas STEC portadoras del denominado locus for enterocyte effacement (LEE) o del locus de adherencia y autoagregación (LAA).

Abstract Shiga Toxin-producing Escherichia coli (STEC) is recognized as being responsible for a large number of foodborne illnesses around the world. The pathogenicity of STEC has been related to Stx toxins. However, the ability of STEC to colonize the host and other surfaces can be essential for developing its pathogenicity. Different virulence profiles detected in STEC could cause the emergence of strains carrying new genes codified in new pathogenicity islands linked to metabolism and adherence. Biofilm formation is a spontaneous mechanism whereby STEC strains resist in a hostile environment being able to survive and consequently infect the host through contaminated food and food contact surfaces. Biofilm formation shows intra-and inter-serotype variability, and its formation does not depend only on the microorganisms involved. Other factors related to the environment (such as pH, temperature) and the surface (stainless steel and polystyrene) influence biofilm expression. The «One Health¼ concept implies the interrelation between public, animal, and environmental health actors to ensure food safety, prevent cross-contamination and resistance to sanitizers, highlighting the need to identify emerging pathogens through new molecular markers of rapid detection that involve STEC strains carrying the Locus of Enterocyte Effacement or Locus of Adhesion and Autoaggregation.

[Shiga toxin producing Escherichia coli: the challenge of adherence to survive]. / Escherichia coli productora de toxina Shiga: el desafío de adherirse para sobrevivir.

Shiga Toxin-producing Escherichia coli (STEC) is recognized as being responsible for a large number of foodborne illnesses around the world. The pathogenicity of STEC has been related to Stx toxins. However, the ability of STEC to colonize the host and other surfaces can be essential for developing its pathogenicity. Different virulence profiles detected in STEC could cause the emergence of strains carrying new genes codified in new pathogenicity islands linked to metabolism and adherence. Biofilm formation is a spontaneous mechanism whereby STEC strains resist in a hostile environment being able to survive and consequently infect the host through contaminated food and food contact surfaces. Biofilm formation shows intra-and inter-serotype variability, and its formation does not depend only on the microorganisms involved. Other factors related to the environment (such as pH, temperature) and the surface (stainless steel and polystyrene) influence biofilm expression. The «One Health¼ concept implies the interrelation between public, animal, and environmental health actors to ensure food safety, prevent cross-contamination and resistance to sanitizers, highlighting the need to identify emerging pathogens through new molecular markers of rapid detection that involve STEC strains carrying the Locus of Enterocyte Effacement or Locus of Adhesion and Autoaggregation.

Protective effect of Lactiplantibacillus plantarum LP5 in a murine model of colonisation by Campylobacter coli DSPV458.

Thermotolerant Campylobacter species are the leading cause of foodborne bacterial diarrheal disease worldwide. Campylobacter coli, abundant in pigs and pork products, have been identified as a source of human infection. In this study, we propose the use of Lactiplantibacillus plantarum LP5 as a probiotic to reduce colonisation of this intestinal pathogen in a murine colonisation model of C. coli DSPV458. Six-week-old adult female Balb/cCmedc mice were housed in groups: Control, Campy and Pro-Campy. Control and Pro-Campy groups received antibiotics for 5 days and the Campy group for 12 days. Pro-Campy group was inoculated for 7 days with 8.78 log10 cfu total of L. plantarum LP5 suspended in De Man, Rogosa and Sharpe broth. All groups were inoculated with 6.72 log10 cfu of C. coli DSPV458 suspended in brain heart infusion broth. L. plantarum LP5 was recovered only in the Pro- Campy group. C. coli DSPV458 was recovered at higher levels in the Control and Campy groups. The differences with the Pro-Campy group were significant. As regards faeces, Control and Campy groups reached 7.41 and 7.84 log10 cfu/g, respectively, and the Pro-Campy group only 4.62 log10 cfu/g. In the caecum, Control and Campy groups reached 8.01 and 9.26 log10cfu/g, respectively, and the Pro-Campy group only 4.51 log10 cfu/g. In the ileum, Control and Campy groups reached 3.43 and 3.26 log10 cfu/g, respectively, and the Pro-Campy group did not show detectable levels. The reduction of C. coli DSPV458 in the Pro-Campy group compared to the Control group in faeces, caecum and ileum was 99.55, 99.98 and 100%, respectively. Animals were maintained under normal health conditions, and haematological parameters were within the standard values for Balb/cCmedc. The incorporation of a probiotic generated a protective effect in the mice colonisation model. The protective effect would also apply to intestinal colonisation by indigenous enterobacteria. Therefore, the strategy used in this study is of great importance to understand the protection mechanisms in a murine model, as well as its application in food-producing animals.

Reduction of Adherence of E. coli O157:H7 to HEp-2 Cells and to Bovine Large Intestinal Mucosal Explants by Colicinogenic E. coli.

Enterohemorrhagic E. coli strains (EHEC) had emerged as foodborne pathogens and cause in human diarrhea and hemolytic-uremic syndrome. Because of the widespread distribution of EHEC serotypes and O157 and non-O157 in cattle population, its control will require interventions at the farm level such as the administration of probiotics that produce inhibitory metabolites. E. coli O157:H7 shows tissue tropisms for the gastrointestinal tract (GIT) of cattle. The aim of this study was to test the ability of a colicinogenic E. coli (isolated from bovine) to reduce the adherence of E. coli O157:H7 to HEp-2 cells and to GIT of cattle. We inoculated HEp-2 cells and bovine colon explants with both kinds of strains. Colicinogenic E. coli was able to reduce the adherence of E. coli O157:H7 to HEp-2 cells and to bovine tissues.

Occurrence of Shiga toxin-producing E. coli (STEC) on carcasses and retail beef cuts in the marketing chain of beef in Argentina.

Argentina has the highest incidence of HUS in the world. HUS is produced by STEC O157 and non-O157. Cattle's faeces and hides are sources of STEC contamination of carcasses during slaughter. We investigated the presence of STEC in carcasses and cuts of meat in the marketing chain in an agricultural city located in Buenos Aires Province (Argentina). In this study, the detection of the stx gene was used as an indicator of carriage of meat with STEC. In carcasses, we detected 12.34% and 18.64% of STEC at the slaughter and sanitary control cabin (place where carcasses arrive from slaughters located outside the city), respectively. These percentages increased at butcheries (24.52%). The 25% of retail beef cuts were STEC-positive with significant differences among the different cuts of meat (chuck: 12.12%, rump roast: 12.12% and minced beef: 40.74%). The stx2 gene was the predominant gene detected in all samples at different levels of the commercialization meat chain.

Escherichia coli with anti-O157:H7 activity isolated from bovine colon.

AIMS: To isolate bacteria from bovine gastrointestinal tract and investigate their inhibitory effect on Escherichia coli O157:H7 in vitro. METHODS AND RESULTS: A total of 2400 bacterial colonies were isolated from cattle colonic mucous membrane. Thirteen strains demonstrated the ability to inhibit the growth of E. coli O157:H7. From these, seven were screened for the presence of virulence factors as: stx(1), stx(2), ehxA, eae, st1a and lt1 by polymerase chain reaction. The selected bacteriocin-producing bacteria showed susceptibility to most of the antibiotics used. CONCLUSIONS: The strains of E. coli isolated, which exhibit inhibitory activity on E. coli O157:H7 growth by the production of inhibitory substances, may be useful in the control of this pathogen in reservoirs. An important characteristic of these strains was the absence of any of the virulence factors assayed and the susceptibility to most of the antibiotics used for Gram-negative bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: These microorganisms might be used as probiotic bacteria to reduce the carriage of E. coli O157:H7 in cattle, thus limiting the contamination of carcasses at slaughter and subsequently the contamination of foods and the transfer of this pathogen to man.

[Isolation and characterization of Shiga-toxin-producing Escherichia coli from frozen hamburgers and soft cheeses]. / Aislamiento y caracterización de Escherichia coli productor de toxina Shiga en hamburguesas supercongeladas y quesos de pasta blanda.

Shiga toxin producing-Escherichia coli (STEC), an important emerging foodborne pathogen, has been associated with bloody and non-bloody diarrhea, hemorrhagic colitis, hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura. The cattle have been shown to be a major reservoir of STEC and raw foods such as ground beef and milk are the most common vehicles of infection. In the present study, the prevalence of STEC in 95 samples of frozen hamburgers and in 114 samples of soft cheese was established in 8.4% and 0.9%, respectively. The genotypic and phenotypic characteristics of the strains were determined. The virulence genes stx1, stx2, eaeA and EHEC-hlyA were identified by PCR and by colony blot hybridization assays. Serotyping, antimicrobial susceptibility and production of Stx using specific cytotoxicity assays on Vero cells were also determined. All STEC strains were characterized as eaeA-/EHEC-hlyA+. The stx2 genotype was prevalent (77.8%), and four different O:H serotypes were found, comprising: O8:H19 (5 strains), O113:H21 (1), O8:H16 (1), and O39:H49 (1). One STEC strain was nontypable. Although soft cheese complimented the microbiological quality controls for the coliform counts, the detection of STEC in one sample raises doubts concerning the effectiveness of the current quality controls. These data contribute to the implementation of strategies for the prevention and control of HUS.

Aislamiento y caracterización de Escherichia coli productor de toxina Shiga en hamburguesas supercongeladas y quesos de pasta blanda. / [Isolation and characterization of Shiga-toxin-producing Escherichia coli from frozen hamburgers and soft cheeses]

Shiga toxin producing-Escherichia coli (STEC), an important emerging foodborne pathogen, has been associated with bloody and non-bloody diarrhea, hemorrhagic colitis, hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura. The cattle have been shown to be a major reservoir of STEC and raw foods such as ground beef and milk are the most common vehicles of infection. In the present study, the prevalence of STEC in 95 samples of frozen hamburgers and in 114 samples of soft cheese was established in 8.4

and 0.9

, respectively. The genotypic and phenotypic characteristics of the strains were determined. The virulence genes stx1, stx2, eaeA and EHEC-hlyA were identified by PCR and by colony blot hybridization assays. Serotyping, antimicrobial susceptibility and production of Stx using specific cytotoxicity assays on Vero cells were also determined. All STEC strains were characterized as eaeA-/EHEC-hlyA+. The stx2 genotype was prevalent (77.8

), and four different O:H serotypes were found, comprising: O8:H19 (5 strains), O113:H21 (1), O8:H16 (1), and O39:H49 (1). One STEC strain was nontypable. Although soft cheese complimented the microbiological quality controls for the coliform counts, the detection of STEC in one sample raises doubts concerning the effectiveness of the current quality controls. These data contribute to the implementation of strategies for the prevention and control of HUS.

Virulence genotypes and serotypes of verotoxigenic Escherichia coli isolated from cattle and foods in Argentina. Importance in public health.

Virulence factors of Verotoxin-producing Escherichia coli (VTEC) strains isolated from hamburgers and ground beef were studied in Argentina by PCR. Their virulence profiles were correlated with those corresponding to strains isolated from calves and adult cattle. Most virulent profiles (VTs+ eae+ Mp+) were present in E. coli from healthy and diarrheic calves corresponding to O5:H-, O5:H27, O20:H?, O26:H11, O38:H?, O103:H-, O103:H2, O111:H-, O118:H16, O165:H-serotypes. The presence of the eae gene was significantly more frequent among VTEC strains isolated from calves (20/26; 76%) than from adult cattle (1/39; 2.5%) (p < 0.005). VT2+ eae- E. coli was prevalent in foods and adult cattle at slaughterhouse. The prevalence of the eae gene was similar between VTEC strains isolated from meat (0/21) and adult cattle (1/39; 2.5%) which constitutes the main population processed at slaughterhouses in Argentina. Serotyping showed that VTEC strains were distributed among 31 serotypes, some of which (O20:H19, O91:H21, O113:H21, O116:H21, O117:H7, O171:H2, OX3:H21) were shared between bovine and food strains. These O serogroups have been isolated from cases of haemorrhagic colitis (HC) and haemolyticuraemic syndrome (HUS) in humans in several continental European countries. This study confirms the role of cattle as a reservoir of many VTEC serotypes other than O157:H7 and represents a base for future diagnostic, prevention and control strategies of EHEC in this country. In addition, this study affirms the advantages of PCR-based screening of E. coli isolates given the finding of so many verotoxin-producing strains.