Summary: Curli are adhesive fimbriae of Escherichia coli and Salmonella enterica . Expression of curli ( csgA ) and cellulose ( bcsA ) is co‐activated by the transcriptional activator CsgD. In this study, we investigated the contribution of curli and cellulose to the adhesive properties of enterohaemorragic (EHEC) O157:H7 and enteropathogenic E. coli (EPEC) O127:H6. While single mutations in csgA , csgD or bcsA in EPEC and EHEC had no dramatic effect on cell adherence, double csgAbcsA mutants were significantly less adherent than the single mutants or wild‐type strains to human colonic HT‐29 epithelial cells or to cow colon tissue in vitro . Overexpression of csgD (carried on plasmid pCP994) in a csgD mutant, but not in the single csgA or bscA mutants, led to significant increase in adherence and biofilm formation in EPEC and EHEC, suggesting that synchronized over‐production of curli and cellulose enhances bacterial adherence. In line with this finding, csgD transcription was activated significantly in the presence of cultured epithelial cells as compared with growth in tissue culture medium. Analysis of the influence of virulence and global regulators in the production of curli in EPEC identified Fis (factor for inversion stimulation) as a, heretofore unrecognized, negative transcriptional regulator of csgA expression. An EPEC E2348/69Δ fis produced abundant amounts of curli whereas a double fis/csgD mutant yielded no detectable curli production. Our data suggest that curli and cellulose act in concert to favour host colonization, biofilm formation and survival in different environments.

Stenotrophomonas maltophilia is an emerging nosocomial bacterial pathogen associated with several infectious diseases and opportunistic infections, especially in immunocompromised patients. These ba...

The basis for the interaction of Brucella species with the surface of epithelial cells before migration in the host within polymorphonuclear leucocytes is largely unknown. Here, we studied the ability of Brucella abortus and Brucella melitensis to adhere to cultured epithelial (HeLa and HEp-2) cells and THP-1-derived macrophages, and to bind extracellular matrix proteins (ECM). The brucellae adhered to epithelial cells forming localized bacterial microcolonies on the cell surface, and this process was inhibited significantly by pretreatment of epithelial cells with neuraminidase and sodium periodate and by preincubation of the bacteria with heparan sulphate and N-acetylneuraminic acid. Trypsinization of epithelial cells yielded increased adherence, suggesting unmasking of target sites on host cells. Notably, the brucellae also adhered to cultured THP-1 cells, and this event was greatly reduced upon removal of sialic acid residues from these cells with neuraminidase. B. abortus bound in a dose-dependent manner to immobilized fibronectin and vitronectin and, to a lesser extent, to chondroitin sulphate, collagen and laminin. In sum, our data strongly suggest that the adherence mechanism of brucellae to epithelial cells and macrophages is mediated by cellular receptors containing sialic acid and sulphated residues. The recognition of ECM (fibronectin and vitronectin) by the brucellae may represent a mechanism for spread within the host tissues. These are novel findings that offer new insights into understanding the interplay between Brucella and host cells.

In the last ten years, Stenotrophomonas maltophilia has gained increasing interest as an important agent of infection, which is why it has come to be recognized as a serious cause of nosocomial infections related to bloodstream infections, pneumonia, and cancer, mainly in patients with intensive care, and is associated with high mortality rates in immunocompromised patients, with prolonged hospital stays and extensive use of antimicrobials. The importance of this microorganism lies in its low pathogenicity, high multiresistance to various antibiotics, and frequent and persistent isolation in predisposed patients. In addition, few studies have evaluated its epidemiology and clinical relevance. The pathogenesis of biofilms lies mainly in the fact that they can generate persistent chronic infections that are difficult to eradicate. To this extent, it is important to make the characteristics of the biofilm formation behavior of Stenotrophomonas maltophilia known and generate more knowledge about its colonization or infection in humans through this review, which discusses more recent information.

The Escherichia coli common pilus (ECP) is produced by commensal and pathogenic E. coli strains. This pilus is unrelated to any of the known colonization factors (CFs) of enterotoxigenic E. coli (ETEC). In this study, we investigated the distribution and production of ECP among a collection of 136 human CF-positive and CF-negative ETEC strains of different geographic origins. The major pilus subunit gene, ecpA , was found in 109 (80%) of these strains, suggesting that it is widely distributed among ETEC strains. Phenotypic analysis of a subset of 43 strains chosen randomly showed that 58% of them produced ECP independently of the presence or absence of CFs, a percentage even higher than that of the most prevalent CFs. These data suggest an important role for ECP in the biology of ETEC, particularly in CF-negative strains, and in human infection.