ABSTRACT
Clostridium perfringens type E is considered a rare toxinotype and an infrequent cause of enterotoxemia of lambs, calves, and rabbits. Until now, only cases of young animal of C. perfringens type E bovine enterotoxemia, characterized by hemorrhagic enteritis and sudden death, have been reported. The present report details the genotypic characterization of C. perfringens type E isolates obtained from intestinal samples of adult cattle during an outbreak of enterotoxemia in Argentina. The sequences of several housekeeping genes of these isolates were analyzed and compared with those obtained from calves in North America showing a clonal unique lineage.
Subject(s)
Cattle Diseases/epidemiology , Clostridium Infections/veterinary , Clostridium perfringens/genetics , Clostridium perfringens/isolation & purification , Death, Sudden/veterinary , Disease Outbreaks/veterinary , Enterotoxemia/epidemiology , Animals , Argentina/epidemiology , Bacterial Proteins/genetics , Cattle , Cattle Diseases/microbiology , Clostridium Infections/epidemiology , Clostridium Infections/microbiology , Clostridium perfringens/classification , Clostridium perfringens/pathogenicity , Death, Sudden/epidemiology , Death, Sudden/etiology , Enterotoxemia/microbiology , Genotype , Molecular Sequence Data , Multilocus Sequence Typing/methods , Polymerase Chain Reaction , Sequence Analysis, DNA , Syndrome , Virulence Factors/geneticsABSTRACT
Enterohemorrhagic Escherichia coli (EHEC), a subset of Shiga toxin producing E. coli (STEC) is associated with a spectrum of diseases that includes diarrhea, hemorrhagic colitis and a life-threatening hemolytic-uremic syndrome (HUS). Regardless of serotype, Shiga toxins (Stx1 and/or Stx2) are uniformly expressed by all EHEC, and so exploitable targets for laboratory diagnosis of these pathogens. In this study, a sandwich ELISA for determination of Shiga toxin (Stx) was developed using anti-Stx2B subunit antibodies and its performance was compared with that of the Vero cell assay and a commercial immunoassay kit. Chicken IgY was used as capture antibody and a HRP-conjugated rabbit IgG as the detection antibody. The anti-Stx2B IgY was harvested from eggs laid by hens immunized with a recombinant protein fragment. Several parameters were tested in order to optimize the sandwich ELISA assay, including concentration of antibodies, type and concentration of blocking agent, and incubation temperatures. Supernatants from 42 STEC strains of different serotypes and stx variants, including stx(2EDL933), stx(2vha), stx(2vhb), stx(2g), stx(1EDL933), and stx(1d) were tested. All Stx variants were detected by the sandwich ELISA, with a detection limit of 115 ng/ml Stx2. Twenty three strains negative for stx genes, including different bacteria species, showed no activity in Vero cell assay and produced negative results in ELISA, except for two strains. Our results show that anti-Stx2B IgY sandwich ELISA could be used in routine diagnosis as a rapid, specific and economic method for detection of Shiga toxin-producing E. coli.
Subject(s)
Antibodies, Bacterial , Bacteriological Techniques/methods , Immunoglobulins , Shiga-Toxigenic Escherichia coli/isolation & purification , Animals , Antibodies, Bacterial/isolation & purification , Cell Survival/drug effects , Chickens , Chlorocebus aethiops , Egg Yolk/chemistry , Enzyme-Linked Immunosorbent Assay/methods , Escherichia coli Infections/diagnosis , Escherichia coli Infections/microbiology , Humans , Immunoglobulins/isolation & purification , Sensitivity and Specificity , Vero CellsABSTRACT
Shiga toxins (Stx1 and Stx2) are the main virulence factors of enterohemorrhagic Escherichia coli (EHEC), a foodborne pathogen associated with diarrhea, hemorrhagic colitis and hemolytic uremic syndrome. The aim of this study was to evaluate the antibodies against Stx2 obtained from egg yolks of laying hens immunized with a recombinant Stx2B subunit. A high specific response in serum was observed 25 days after the first immunization and IgY antibodies were extracted from day 47th and purified from egg yolk. A concentration of 0.84 mg of total IgY/ml of egg yolk was obtained, of which 8% were antigen specific. The ability of anti-Stx2B IgY to recognize Stx2B and Stx2 either in solid-phase or in solution were evaluated and compared with anti-Stx2B rabbit antibodies by Western blotting and ELISA. The protective efficacy of IgY against Stx2 was determined by in vitro and in vivo experiments. The results show that IgY was able to recognize Stx2B and Stx2 in denatured conditions, attached to a solid-phase and free in solution. The anti-Stx2B IgY could effectively block the biological activity of Stx2 on Vero cells and protect mice from Stx2 challenge. The data suggest that immunization of hens with Stx2B could be a strategy to obtain at low cost a relatively high concentration of anti-Stx2 egg yolk IgY, able to neutralize Stx2 lethal activity. IgY technology could be an useful tool for research, diagnosis and therapy of EHEC infection.
