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  • 1
    Online Resource
    Online Resource
    Serologic Evidence for Effective Production of Cytolysin A in Salmonella enterica Serovars Typhi and Paratyphi A during Human Infection
    American Society for Microbiology ; 2006
    In:  Infection and Immunity Vol. 74, No. 11 ( 2006-11), p. 6505-6508
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 74, No. 11 ( 2006-11), p. 6505-6508
    Abstract: ClyA STy and ClyA SPaA are closely related pore-forming cytolysins of Salmonella enterica serovars Typhi and Paratyphi A whose expression is strongly repressed under standard in vitro growth conditions. We show here that human infections by these pathogens cause a specific antibody response to ClyA, indicating effective toxin production during infection.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00779-06
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2006
    detail.hit.zdb_id: 1483247-1
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  • 2
    Online Resource
    Online Resource
    Differential Regulation of Multiple Proteins of Escherichia coli and Salmonella enterica Serovar Typhimurium by the Transcriptional Regulator SlyA
    American Society for Microbiology ; 2002
    In:  Journal of Bacteriology Vol. 184, No. 13 ( 2002-07), p. 3549-3559
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 184, No. 13 ( 2002-07), p. 3549-3559
    Abstract: SlyA is a transcriptional regulator of Escherichia coli , Salmonella enterica , and other bacteria belonging to the Enterobacteriaceae . The SlyA protein has been shown to be involved in the virulence of S. enterica serovar Typhimurium, but its role in E. coli is unclear. In this study, we employed the proteome technology to analyze the SlyA regulons of enteroinvasive E. coli (EIEC) and Salmonella serovar Typhimurium. In both cases, comparative analysis of the two-dimensional protein maps of a wild-type strain, a SlyA-overproducing derivative, and a corresponding slyA mutant revealed numerous proteins whose expression appeared to be either positively or negatively controlled by SlyA. Twenty of the putative SlyA-induced proteins and 13 of the putative SlyA-repressed proteins of the tested EIEC strain were identified by mass spectrometry. The former proteins included several molecular chaperones (GroEL, GroES, DnaK, GrpE, and CbpA), proteins involved in acid resistance (HdeA, HdeB, and GadA), the “starvation lipoprotein” (Slp), cytolysin ClyA (HlyE or SheA), and several enzymes involved in metabolic pathways, whereas most of the latter proteins proved to be biosynthetic enzymes. Consistently, the resistance of the EIEC slyA mutant to heat and acid stress was impaired compared to that of the wild-type strain. Furthermore, the implication of SlyA in the regulation of several of the identified E. coli proteins was confirmed at the level of transcription with lacZ fusions. Twenty-three of the Salmonella serovar Typhimurium proteins found to be affected by SlyA were also identified by mass spectrometry. With the exception of GroEL these differed from those identified in the EIEC strain and included proteins involved in various processes. The data suggest that gene regulation by SlyA might be crucial for intracellular survival and/or replication of both EIEC and Salmonella serovar Typhimurium in phagocytic host cells.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.184.13.3549-3559.2002
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2002
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Molecular Analysis of Cytolysin A (ClyA) in Pathogenic Escherichia coli Strains
    American Society for Microbiology ; 2004
    In:  Journal of Bacteriology Vol. 186, No. 16 ( 2004-08-15), p. 5311-5320
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 186, No. 16 ( 2004-08-15), p. 5311-5320
    Abstract: Cytolysin A (ClyA) of Escherichia coli is a pore-forming hemolytic protein encoded by the clyA ( hlyE , sheA ) gene that was first identified in E. coli K-12. In this study we examined various clinical E. coli isolates with regard to the presence and integrity of clyA . PCR and DNA sequence analyses demonstrated that 19 of 23 tested Shiga toxin-producing E. coli (STEC) strains, all 7 tested enteroinvasive E. coli (EIEC) strains, 6 of 8 enteroaggregative E. coli (EAEC) strains, and 4 of 7 tested enterotoxigenic E. coli (ETEC) strains possess a complete clyA gene. The remaining STEC, EAEC, and ETEC strains and 9 of the 17 tested enteropathogenic E. coli (EPEC) strains were shown to harbor mutant clyA derivatives containing 1-bp frameshift mutations that cause premature termination of the coding sequence. The other eight EPEC strains and all tested uropathogenic and new-born meningitis-associated E. coli strains ( n = 14 and 3, respectively) carried only nonfunctional clyA fragments due to the deletion of two sequences of 493 bp and 204 or 217 bp at the clyA locus. Expression of clyA from clinical E. coli isolates proved to be positively controlled by the transcriptional regulator SlyA. Several tested E. coli strains harboring a functional clyA gene produced basal amounts of ClyA when grown under standard laboratory conditions, but most of them showed a clyA -dependent hemolytic phenotype only when SlyA was overexpressed. The presented data indicate that cytolysin A can play a role only for some of the pathogenic E. coli strains.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.186.16.5311-5320.2004
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2004
    detail.hit.zdb_id: 1481988-0
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  • 4
    Online Resource
    Online Resource
    Characterization of Anti- Salmonella enterica Serotype Typhi Antibody Responses in Bacteremic Bangladeshi Patients by an Immunoaffinity Proteomics-Based Technology
    American Society for Microbiology ; 2010
    In:  Clinical and Vaccine Immunology Vol. 17, No. 8 ( 2010-08), p. 1188-1195
    Details
    In: Clinical and Vaccine Immunology, American Society for Microbiology, Vol. 17, No. 8 ( 2010-08), p. 1188-1195
    Abstract: Salmonella enterica serotype Typhi is the cause of typhoid fever and a human-restricted pathogen. Currently available typhoid vaccines provide 50 to 90% protection for 2 to 5 years, and available practical diagnostic assays to identify individuals with typhoid fever lack sensitivity and/or specificity. Identifying immunogenic S . Typhi antigens expressed during human infection could lead to improved diagnostic assays and vaccines. Here we describe a platform i mmunoaffinity p roteomics-based t echnology (IPT) that involves the use of columns charged with IgG, IgM, or IgA antibody fractions recovered from humans bacteremic with S . Typhi to capture S . Typhi proteins that were subsequently identified by mass spectrometry. This screening tool identifies immunogenic proteins recognized by antibodies from infected hosts. Using this technology and the plasma of patients with S . Typhi bacteremia in Bangladesh, we identified 57 proteins of S. Typhi, including proteins known to be immunogenic (PagC, HlyE, OmpA, and GroEL) and a number of proteins present in the human-restricted serotypes S . Typhi and S . Paratyphi A but rarely found in broader-host-range Salmonella spp. (HlyE, CdtB, PltA, and STY1364). We categorized identified proteins into a number of major groupings, including those involved in energy metabolism, protein synthesis, iron homeostasis, and biosynthetic and metabolic functions and those predicted to localize to the outer membrane. We assessed systemic and mucosal anti-HlyE responses in S . Typhi-infected patients and detected anti-HlyE responses at the time of clinical presentation in patients but not in controls. These findings could assist in the development of improved diagnostic assays.
    Type of Medium: Online Resource
    ISSN: 1556-6811 , 1556-679X
    URL: Article
    DOI: 10.1128/CVI.00104-10
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2010
    detail.hit.zdb_id: 1496863-0
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  • 5
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    Online Resource
    Biological Cost of Rifampin Resistance from the Perspective of Staphylococcus aureus
    American Society for Microbiology ; 2002
    In:  Antimicrobial Agents and Chemotherapy Vol. 46, No. 11 ( 2002-11), p. 3381-3385
    Details
    In: Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 46, No. 11 ( 2002-11), p. 3381-3385
    Abstract: Resistance determinants that interfere with normal physiological processes in the bacterial cell usually cause a reduction in biological fitness. Fitness assays revealed that 17 of 18 in vitro-selected chromosomal mutations within the rpoB gene accounting for rifampin resistance in Staphylococcus aureus were associated with a reduction in the level of fitness. There was no obvious correlation between the level of resistance to rifampin and the level of fitness loss caused by rpoB mutations. Among 23 clinical rifampin-resistant S. aureus isolates from six countries, only seven different rpoB genotypes could be identified, whereby the mutation 481His→Asn was present in 21 (91%) of these 23 isolates. The mutation 481His→Asn, in turn, which confers low-level rifampin resistance on its own, was not shown to be associated with a cost of resistance in vitro. The restriction to distinct mutations that confer rifampin resistance in vivo, as demonstrated here, appears to be determined by the Darwinian fitness of the organisms.
    Type of Medium: Online Resource
    ISSN: 0066-4804 , 1098-6596
    URL: Article
    DOI: 10.1128/AAC.46.11.3381-3385.2002
    RVK:
    XA 24552
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2002
    detail.hit.zdb_id: 1496156-8
    SSG: 12
    SSG: 15,3
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  • 6
    Online Resource
    Online Resource
    Linezolid Resistance in Staphylococcus aureus : Gene Dosage Effect, Stability, Fitness Costs, and Cross-Resistances
    American Society for Microbiology ; 2008
    In:  Antimicrobial Agents and Chemotherapy Vol. 52, No. 4 ( 2008-04), p. 1570-1572
    Details
    In: Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 52, No. 4 ( 2008-04), p. 1570-1572
    Abstract: Linezolid resistance in Staphylococcus aureus is typically associated with mutations in the 23S rRNA gene. Here we show that the accumulation of a single point mutation, G2576T, in the different copies of this gene causes stepwise increases in resistance, impairment of the biological fitness, and cross-resistance to quinupristin-dalfopristin and chloramphenicol.
    Type of Medium: Online Resource
    ISSN: 0066-4804 , 1098-6596
    URL: Article
    DOI: 10.1128/AAC.01098-07
    RVK:
    XA 24552
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2008
    detail.hit.zdb_id: 1496156-8
    SSG: 12
    SSG: 15,3
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  • 7
    Online Resource
    Online Resource
    Mutations Affecting Export and Activity of Cytolysin A from Escherichia coli
    American Society for Microbiology ; 2010
    In:  Journal of Bacteriology Vol. 192, No. 15 ( 2010-08), p. 4001-4011
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 192, No. 15 ( 2010-08), p. 4001-4011
    Abstract: Cytolysin A (known as ClyA, HlyE, and SheA) is a cytolytic pore-forming protein toxin found in several Escherichia coli and Salmonella enterica strains. The structure of its water-soluble monomeric form and that of dodecameric ClyA pores is known, but the mechanisms of ClyA export from bacterial cells and of pore assembly are only partially understood. Here we used site-directed mutagenesis to study the importance of different regions of the E. coli ClyA protein for export and activity. The data indicate that ClyA translocation to the periplasm requires several protein segments located closely adjacent to each other in the “tail” domain of the ClyA monomer, namely, the N- and C-terminal regions and the hydrophobic sequence ranging from residues 89 to 101. Deletion of most of the “head” domain of the monomer (residues 181 to 203), on the other hand, did not strongly affect ClyA secretion, suggesting that the tail domain plays a particular role in export. Furthermore, we found that the N-terminal amphipathic helix αA1 of ClyA is crucial for the formation and the properties of the transmembrane channel, and hence for hemolytic activity. Several mutations affecting the C-terminal helix αG, the “β-tongue” region in the head domain, or the hydrophobic region in the tail domain of the ClyA monomer strongly impaired the hemolytic activity and reduced the activity toward planar lipid bilayer membranes but did not totally prevent formation of wild-type-like channels in these artificial membranes. The latter regions thus apparently promote membrane interaction without being directly required for pore formation in a lipid bilayer.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.01283-09
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2010
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 8
    Online Resource
    Online Resource
    Immunoproteomic Analysis of Antibody in Lymphocyte Supernatant in Patients with Typhoid Fever in Bangladesh
    American Society for Microbiology ; 2014
    In:  Clinical and Vaccine Immunology Vol. 21, No. 3 ( 2014-03), p. 280-285
    Details
    In: Clinical and Vaccine Immunology, American Society for Microbiology, Vol. 21, No. 3 ( 2014-03), p. 280-285
    Abstract: We have previously shown that an assay based on detection of anti- Salmonella enterica serotype Typhi antibodies in supernatant of lymphocytes harvested from patients presenting with typhoid fever (antibody in lymphocyte supernatant [ALS] assay) can identify 100% of patients with blood culture-confirmed typhoid fever in Bangladesh. In order to define immunodominant proteins within the S . Typhi membrane preparation used as antigen in these prior studies and to identify potential biomarkers unique to S . Typhi bacteremic patients, we probed microarrays containing 2,724 S . Typhi proteins with ALS collected at the time of clinical presentation from 10 Bangladeshis with acute typhoid fever. We identified 62 immunoreactive antigens when evaluating both the IgG and IgA responses. Immune responses to 10 of these antigens discriminated between individuals with acute typhoid infection and healthy control individuals from areas where typhoid infection is endemic, as well as Bangladeshi patients presenting with fever who were subsequently confirmed to have a nontyphoid illness. Using an ALS enzyme-linked immunosorbent assay (ELISA) format and purified antigen, we then confirmed that immune responses against the antigen with the highest immunoreactivity (hemolysin E [HlyE]) correctly identified individuals with acute typhoid or paratyphoid fever in Dhaka, Bangladesh. These observations suggest that purified antigens could be used with ALS and corresponding acute-phase activated B lymphocytes in diagnostic platforms to identify acutely infected patients, even in areas where enteric fever is endemic.
    Type of Medium: Online Resource
    ISSN: 1556-6811 , 1556-679X
    URL: Article
    DOI: 10.1128/CVI.00661-13
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2014
    detail.hit.zdb_id: 1496863-0
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  • 9
    Online Resource
    Online Resource
    Compensatory Adaptation to the Loss of Biological Fitness Associated with Acquisition of Fusidic Acid Resistance in Staphylococcus aureus
    American Society for Microbiology ; 2005
    In:  Antimicrobial Agents and Chemotherapy Vol. 49, No. 4 ( 2005-04), p. 1426-1431
    Details
    In: Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 49, No. 4 ( 2005-04), p. 1426-1431
    Abstract: Recent studies have shown that individual amino acid exchanges within elongation factor G (EF-G) cause fusidic acid resistance in Staphylococcus aureus . The data from the present study illustrate that the fusidic acid resistance-mediating amino acid substitutions P406L and H457Y are associated with a marked impairment of the biological fitness of S. aureus . In particular, strains producing EF-G derivatives with these mutations showed reduced growth, decreased plasma coagulase activity, and an impaired capability to compete with the isogenic wild-type strain. Second-site mutations within EF-G, such as A67T and S416F, that have been encountered in clinical fusidic acid-resistant isolates containing the amino acid exchanges P406L and H457Y, respectively, were shown not to contribute to resistance. Furthermore, the substitution A67T had no impact on the biological fitness in vitro. The exchange S416F, however, was found to function as a fitness-compensating mutation in S. aureus carrying the substitution H457Y in EF-G. In conclusion, the data presented in this report provide evidence at the molecular level that the deleterious effects of fusidic acid resistance-mediating exchanges within EF-G of S. aureus can be reduced considerably by specific compensating mutations in this target protein. This compensatory adaptation most likely plays a significant role in the stabilization of resistant bacteria within a given population.
    Type of Medium: Online Resource
    ISSN: 0066-4804 , 1098-6596
    URL: Article
    DOI: 10.1128/AAC.49.4.1426-1431.2005
    RVK:
    XA 24552
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2005
    detail.hit.zdb_id: 1496156-8
    SSG: 12
    SSG: 15,3
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