Native Shigella Flexneri

The Shigella species cause millions of cases of watery or bloody diarrhea each year, mostly in children in developing countries. While many aspects of Shigella colonic cell invasion are known, crucial gaps in knowledge regarding how the bacteria survive, transit, and regulate gene expression prior to infection remain. In this study, we define mechanisms of resistance to bile salts and build on previous research highlighting induced virulence in Shigella flexneri strain 2457T following exposure to bile salts. Typical growth patterns were observed within the physiological range of bile salts; however, growth was inhibited at higher concentrations. Interestingly, extended periods of exposure to bile salts led to biofilm formation, a conserved phenotype that we observed among members of the Enterobacteriaceae. Characterization of S. flexneri 2457T biofilms determined that both bile salts and glucose were required for formation, dispersion was dependent upon bile salts depletion, and recovered bacteria displayed induced adherence to HT-29 cells. RNAsequencing analysis verified an important bile salt transcriptional profile in S. flexneri 2457T, including induced drug resistance and virulence gene expression. Finally, functional mutagenesis identified the importance of the AcrAB efflux pump and lipopolysaccharide O-antigen synthesis for bile salt resistance. Our data demonstrate that S. flexneri 2457T employs multiple mechanisms to survive exposure to bile salts, which may have important implications for multidrug resistance. Furthermore, our work confirms that bile salts are important physiological signals to activate S. flexneri 2457T virulence. This work provides insights into how exposure to bile likely regulates Shigella survival and virulence during host transit and subsequent colonic infection.

Reactions of copper(II) acetate with 2-thiouracil (tucH(2)) and triphenyl phosphine (1:1:1 or 1:1:2 molar ratios) in methanol-acetonitrile/chloroform mixture yielded a light brown N,S-bridged dinuclear Cu-I complex, [Cu(PPh3)(2)(mu-N,S-tucH)Cu(PPh3)(2)Cl] 1, incorporating uninegative 2-thiouracilate. X-ray crystallography has shown that the crystals of complex 1 comprise a two component twin system and belong to the space group Ia. The major component 1a is about 77% and the minor component 1b is about 23%. One Cu is four-coordinate tetrahedral with center {CuP2SCl} and the other Cu is three-coordinate distorted trigonal planar with {CuP2N} center. Crystal data: 1, formula, C76H63ClCu2N2OP4S; space group: Ia; monoclinic, a, 22.2638(9); b, 11.8050(4); c, 27.4455(10) angstrom; beta, 113.358(5); R, 4.80%;173(2) K. The antimicrobial activities of dinuclear 1 as well as that of the previously reported 2-thiouracil, 2,4,6-trimercaptotriazine (tmtH(3)) and purine-6-thione (purSH(2)) complexes, [CuCl(kappa(1)-S-tucH(2))(PPh3)(2)] 2, [Cu2Br2(mu-S-tucH(2))(2)(PPh3)(2)] 3, [Cu(tmtH(2))(PPh3)(2)] 4, [Cu3Br2(k(1)-N,k(1)-S,mu-S-tmtH(2))(PPh3)(6)] 5 and [Cu(k(1)-N,k(1)-S-purSH)(PPh3)(2)] 6, have been screened against gram negative, Escherichia coli (MTCC 119) and Shigella flexneri (MTCC 1457), gram positive, Enterococcus faecalis (MTCC 439) and Staphylococcus aureus (MTCC 740) microorganism. High percentage of cell viability (96-97%) is observed in some cases. [GRAPHICS] .