2024-03-29T09:30:47Zhttp://repository.helmholtz-hzi.de/oai/requestoai:repository.helmholtz-hzi.de:10033/2756122019-08-30T11:32:41Zcom_10033_306379com_10033_620636col_10033_306382col_10033_620637
00925njm 22002777a 4500
dc
Bruchmann, Sebastian
author
Dötsch, Andreas
author
Nouri, Bianka
author
Chaberny, Iris F
author
Häussler, Susanne
author
2013-03
Quinolone antibiotics constitute a clinically successful and widely used class of broad-spectrum antibiotics; however, the emergence and spread of resistance increasingly limits the use of fluoroquinolones in the treatment and management of microbial disease. In this study, we evaluated the quantitative contributions of quinolone target alteration and efflux pump expression to fluoroquinolone resistance in Pseudomonas aeruginosa. We generated isogenic mutations in hot spots of the quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, and parC and inactivated the efflux regulator genes so as to overexpress the corresponding multidrug resistance (MDR) efflux pumps. We then introduced the respective mutations into the reference strain PA14 singly and in various combinations. Whereas the combined inactivation of two efflux regulator-encoding genes did not lead to resistance levels higher than those obtained by inactivation of only one efflux regulator-encoding gene, the combination of mutations leading to increased efflux and target alteration clearly exhibited an additive effect. This combination of target alteration and overexpression of efflux pumps was commonly observed in clinical P. aeruginosa isolates; however, these two mechanisms were frequently found not to be sufficient to explain the level of fluoroquinolone resistance. Our results suggest that there are additional mechanisms, independent of the expression of the MexAB-OprM, MexCD-OprJ, MexEF-OprN, and/or MexXY-OprM efflux pump, that increase ciprofloxacin resistance in isolates with mutations in the QRDRs.
Quantitative Contributions of Target Alteration and Decreased Drug Accumulation to Pseudomonas aeruginosa Fluoroquinolone Resistance. 2013, 57 (3):1361-8 Antimicrob. Agents Chemother.
1098-6596
23274661
10.1128/AAC.01581-12
http://hdl.handle.net/10033/275612
Antimicrobial agents and chemotherapy
Quantitative Contributions of Target Alteration and Decreased Drug Accumulation to Pseudomonas aeruginosa Fluoroquinolone Resistance.
oai:repository.helmholtz-hzi.de:10033/3384912019-08-30T11:26:42Zcom_10033_306379com_10033_620636col_10033_306382col_10033_620637
00925njm 22002777a 4500
dc
Blanka, Andrea
author
Schulz, Sebastian
author
Eckweiler, Denitsa
author
Franke, Raimo
author
Bielecka, Agata
author
Nicolai, Tanja
author
Casilag, Fiordiligie
author
Düvel, Juliane
author
Abraham, Wolf-Rainer
author
Kaever, Volkhard
author
Häussler, Susanne
author
2014-01
Pseudomonas aeruginosa is distinguished by its broad metabolic diversity and its remarkable capability for adaptation, which relies on a large collection of transcriptional regulators and alternative sigma (σ) factors. The largest group of alternative σ factors is that of the extracytoplasmic function (ECF) σ factors, which control key transduction pathways for maintenance of envelope homeostasis in response to external stress and cell growth. In addition, there are specific roles of alternative σ factors in regulating the expression of virulence and virulence-associated genes. Here, we analyzed a deletion mutant of the ECF σ factor SigX and applied mRNA profiling to define the SigX-dependent regulon in P. aeruginosa in response to low-osmolarity-medium conditions. Furthermore, the combination of transcriptional data with chromatin immunoprecipitation (ChIP) followed by high-throughput sequencing (ChIP-seq) led to the identification of the DNA binding motif of SigX. Genome-wide mapping of SigX-binding regions revealed enrichment of downstream genes involved in fatty acid biosynthesis, type III secretion, swarming and cyclic di-GMP (c-di-GMP) signaling. In accordance, a sigX deletion mutant exhibited altered fatty acid composition of the cell membrane, reduced cytotoxicity, impaired swarming activity, elevated c-di-GMP levels, and increased biofilm formation. In conclusion, a combination of ChIP-seq with transcriptional profiling and bioinformatic approaches to define consensus DNA binding sequences proved to be effective for the elucidation of the regulon of the alternative σ factor SigX, revealing its role in complex virulence-associated phenotypes in P. aeruginosa.
Identification of the alternative sigma factor SigX regulon and its implications for Pseudomonas aeruginosa pathogenicity. 2014, 196 (2):345-56 J. Bacteriol.
1098-5530
24187091
10.1128/JB.01034-13
http://hdl.handle.net/10033/338491
Journal of bacteriology
Identification of the alternative sigma factor SigX regulon and its implications for Pseudomonas aeruginosa pathogenicity.
oai:repository.helmholtz-hzi.de:10033/3441212021-07-05T15:12:59Zcom_10033_306379com_10033_622921col_10033_622922col_10033_306382
00925njm 22002777a 4500
dc
Marandu, Thomas F
author
Finsterbusch, Katja
author
Kröger, Andrea
author
Čičin-Šain, Luka
author
2014-06
Poor immune protection upon vaccination is a critical determinant of immunosenescence. Latent Cytomegalovirus (CMV) infection has been associated with poor antibody responses to vaccination, but a causative role for CMV in the poor immune response requires experimental evidence and thus could not be confirmed in clinical studies. To test the hypothesis that latent CMV infection causes poor antibody responses, we infected young or adult mice with mouse CMV and challenged them with Vesicular stomatitis virus (VSV) at 15 or 18months of age. Latent, but not primary infection with mouse CMV resulted in diminished neutralizing titers of the serum IgG fraction at day 7 post challenge, which recovered by day 14 post challenge. This phenomenon was specific for mice infected with mouse CMV, but not mice infected with other herpesviruses, like murine herpesvirus-68 or herpes simplex virus type 1, or mice infected with non-persistent viruses, such as influenza or Vaccinia virus. Hence, our data indicate a delay in IgG class-switch that was specific for the CMV infection. Herpesviral infections did not change the B-cell memory compartment, and increased the size of the effector-memory subset of blood CD4 T-cells only when administered in combination. Furthermore, CD4 T-cell response to VSV infection was maintained in latently infected mice. Therefore, our results argue that latent CMV infection impairs B-cell, but not T-cell responses to a challenge with VSV and delays antibody class-switch by a mechanism which may be independent of T-cell help.
Mouse CMV infection delays antibody class switch upon an unrelated virus challenge. 2014, 54:101-8 Exp. Gerontol.
1873-6815
24462805
10.1016/j.exger.2014.01.017
http://hdl.handle.net/10033/344121
Experimental gerontology
Mouse CMV infection delays antibody class switch upon an unrelated virus challenge.