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Resistance Phenotypes and Genotypes of Erythromycin-Resistant Streptococcus pneumoniae Isolates in Beijing and Shenyang, China. Zhao Tiemei, 2004.Of a total of 192 Streptococcus pneumoniae isolates, 149 (77.6%) were not susceptible to erythromycin . Of these 149 isolates, 117 (79.1%) contained the erm(B) gene, 16 (10.8%) contained the mef(A) gene, and 15 (10.1%) harbored both the erm(B) and mef(A) genes . Azithromycin Inhibits MUC5AC Production Induced by the Pseudomonas aeruginosa Autoinducer N-(3-Oxododecanoyl) Homoserine Lactone in NCI-H292 Cells. Yoshifumi Imamura, 2004.The features of chronic airway diseases, including chronic bronchitis, cystic fibrosis, bronchiectasis, and diffuse panbronchiolitis, include chronic bacterial infection and airway obstruction by mucus . Pseudomonas aeruginosa is one of the most common pathogens in chronic lung infection, and quorum-sensing systems contribute to the pathogenesis of this disease . The quorum-sensing signal molecule [N-(3-oxododecanoyl) homoserine lactone (3O-C12-HSL)] not only regulates bacterial virulence but also is associated with the immune response . In this study, we investigated whether 3O-C12-HSL could stimulate the production of a major mucin core protein, MUC5AC . The effect of a macrolide on MUC5AC production was also studied . 3O-C12-HSL induced NCI-H292 cells to express MUC5AC at both the mRNA and the protein levels in time- and dose-dependent manners . A 15-membered macrolide, azithromycin, inhibited MUC5AC production that was activated by 3O-C12-HSL . 3O-C12-HSL induced extracellular signal-regulated kinase (ERK) 1/2 and I-  B phosphorylation in cells, and this induction was suppressed by azithromycin . 3O-C12-HSL-induced MUC5AC production was blocked by the ERK pathway inhibitor PD98059 . Our findings suggest that the P . aeruginosa autoinducer 3O-C12-HSL contributes to excessive mucin production in chronic bacterial infection . Azithromycin seems to reduce this mucin production by interfering with intracellular signal transduction .
Identification of the cis-Acting Site Involved in Activation of Promoters Regulated by Activity of the Type III Secretion Apparatus in Shigella flexneri. Maria Mavris, 2002.Bacteria of Shigella spp . use a virulence plasmid-encoded type III secretion (TTS) system to invade the colonic epithelium in humans . The activity of the TTS apparatus is tightly regulated in the wild-type strain and is induced upon contact of bacteria with epithelial cells, whereas it is deregulated, i.e., constitutively active, in some mutants . Under conditions of deregulated secretion, approximately 20 proteins are secreted, including VirA, OspB to OspG, and at least three members of the IpaH family, all of which are encoded by the virulence plasmid . Conditions inducing or deregulating the activity of secretion also induce the transcription of virA and four ipaH genes . The transcription of virA and ipaH9.8 requires both MxiE, a transcriptional activator of the AraC family, and IpgC, the chaperone of IpaB and IpaC, acting as a coactivator . Using reporter plasmids containing lacZ transcriptional fusions, we showed that the ipaH7.8 . ipa4.5 . ospC1, and ospF promoters are activated under conditions of deregulated secretion and that both MxiE and IpgC are necessary and sufficient for their activation in both Shigella flexneri and Escherichia coli . Promoter mapping and deletion analysis of the ipaH9.8 . virA, and ospC1 promoters identified a 17-bp motif, the MxiE box, which overlaps the -35 region and is essential for the activation of these promoters . The presence of eight MxiE boxes on the virulence plasmid suggests that 11 genes encoding secreted proteins may be regulated by the activity of secretion . We also present evidence that at least one ipaH gene that is carried by the chromosome is controlled by MxiE and IpgC . Mycobacterium tuberculosis Chaperonin 10 Is Secreted in the Macrophage Phagosome: Is Secretion Due to Dissociation and Adoption of a Partially Helical Structure at the Membrane?. Gianluca Fossati, 2003.To confirm that Mycobacterium tuberculosis chaperonin 10 (Cpn10) is secreted outside the live bacillus, infected macrophages were examined by electron microscopy . This revealed that the mycobacterial protein accumulates both in the wall of the bacterium and in the matrix of the phagosomes in which ingested mycobacteria survive within infected macrophages . To understand the structural implications underlying this secretion, a structural study of M . tuberculosis Cpn10 was performed under conditions that are generally believed to mimic the membrane environment . It was found that in buffer-organic solvent mixtures, the mycobacterial protein forms two main species, namely, a partially helical monomer that prevails in dilute solutions at room temperature and a dimer that folds into a ß-sheet-dominated structure and prevails in either concentrated protein solutions at room temperature or in dilute solutions at low temperature . A partially helical monomer was also found and was completely associated with negatively charged detergents in a micelle-bound state . Remarkably, zwitterionic lipids had no effect on the protein structure . By using N- and C-truncated forms of the protein, the C- and N-terminal sequences were identified as possessing an amphiphilic helical character and as selectively associating with acidic detergent micelles . When the study was extended to other chaperonins, it was found that human Cpn10 is also monomeric and partially helical in dilute organic solvent-buffer mixtures . In contrast, Escherichia coli Cpn10 is mostly dimeric and predominately ß-sheet in both dilute and concentrated solutions . Interestingly, human Cpn10 also crosses biological membranes, whereas the E . coli homologue is strictly cytosolic . These results suggest that dissociation to partially helical monomers and interaction with acidic lipids may be two important steps in the mechanism of secretion of M . tuberculosis Cpn10 to the external environment .
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