SummaryThe Rhs family comprises a set of composite elements found in the chromosomes of many natural Escherichia coii strains.

Certain Escherichia coli strains bind the Fc fragment of immunoglobulin G (IgG) at the bacterial cell surface. Previous work established that this nonimmune Ig binding depends on several large proteins with apparent molecular masses that can exceed 200 kDa. For E. coli strain ECOR-9, four distinct genes (designated eibA, eibC, eibD, and eibE) are responsible for Ig binding. Two eib genes are linked to eaa genes, which are homologous to genes for the autotransporter family of secreted proteins. With reference to the E. coli K-12 chromosome, the eibA-eaaA cluster is adjacent to trpA (min 28.3) while the eibC-eaaC cluster is adjacent to aspS (min 42.0). Sequence adjacent to the eibA-eaaA cluster converges with that of strain K-12 precisely as observed for the Atlas family of prophages, suggesting that eibA is part of one of these. All four eib genes, when cloned into plasmid vectors, impart IgG binding to E. coli K-12 strains, and three impart IgA binding also. The IgG binding occurs at the bacterial cell surface, and its expression increases survival in serum by up to 3 orders of magnitude. The eib sequences predict a C-terminal peptide motif that is characteristic of outer membrane proteins, and the protein sequences show significant similarity near the C terminus to both the YadA virulence factor of Yersinia species and the universal surface protein A II of Moraxella catarrhalis. The sizes predicted for Eib proteins from DNA sequence are much smaller than their apparent sizes on sodium dodecyl sulfatepolyacrylamide gel electrophoresis, possibly reflecting stable oligomerization.Proteins which bind immunoglobulins (Ig) in a nonimmune manner have been identified in numerous bacteria, and some are thought to play a role in virulence (summarized in reference 32). We previously found that six Escherichia coli strains from the ECOR (E. coli reference) collection exhibit Ig-binding activity (32). The responsible proteins are located on the surface of the cells, where they can be destroyed by limited proteolysis. The nonimmune nature is emphasized by the fact that the binding requires only the Fc fragment of IgG. The binding activity takes the form of several large proteins, some with apparent molecular masses exceeding 200 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In immunoblots, these proteins are seen as multiple bands, with no two strains having the same banding pattern. Expression of these proteins in ECOR-9, the E. coli strain selected for this study, is favored by growth at 37°C and by entry into stationary phase. Interestingly, the material will bind Ig both as native protein on the cell surface and after being subjected to the denaturing conditions that accompany SDS-PAGE. The goal of the present work was to determine the genetic basis of the Ig binding and the complexity of the observed banding patterns. We report the characterization of a family of eib genes (for "E. coli Ig binding") from ECOR-9, a strain of E. coli isolated from the feces of a healthy Swedish schoolchild (...

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Dry dog and cat foods manufactured at plant X were linked to human illness for a 3-year period. This outbreak highlights the importance of proper handling and storage of pet foods in the home to prevent human illness, especially among young children.