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Response of Staphylococcus aureus to subinhibitory concentrations of a sequence-selective, DNA minor groove cross-linking pyrrolobenzodiazepine dimer.

ABSTRACT: ELB-21 is a pyrrolo[2,1-c][1,4]benzodiazepine dimer with potent antistaphylococcal activity; it binds covalently to guanine residues on opposing strands of duplex DNA, interfering with regulatory proteins and transcription elongation in a sequence-selective manner. Transcriptional and proteomic alterations induced by exposure of Staphylococcus aureus clinical isolate EMRSA-16 to ELB-21 were determined in order to define more precisely the bactericidal mechanism of the drug.DNase I footprinting was used to identify high-affinity DNA binding sites. Microarrays and gel electrophoresis were used to assess the ELB-21-induced phenotype.High-affinity interstrand binding sites in which guanine residues were separated by 4 bp, and also some intrastrand cross-linking sites of variable length were identified. Exposure of EMRSA-16 to 0.015 mg/L ELB-21 elicited a 2-fold or greater up-regulation of 168 genes in logarithmic phase and 181 genes in stationary phase; the majority of genes affected were associated with resident prophages Sa2 and Sa3, pathogenicity island SaPI4 and DNA damage repair. ELB-21 induced a marked increase in the number of viable phage particles in culture supernatants. The expression of only a limited number of genes showed a >50% reduction. Sixteen extracellular and four intracellular proteins were differentially expressed during logarithmic and stationary phases, including RecA, proteins associated with staphylococcal pathogenesis (IsaA, CspA), cell division and wall synthesis.ELB-21 kills S. aureus by forming multiple interstrand and intrastrand DNA cross-links, resulting in induction of the DNA damage response, derepression of resident prophages and modulation of a limited number of genes involved with cell wall synthesis.

SUBMITTER: Doyle M

PROVIDER: S-EPMC2764867 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

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Response of Staphylococcus aureus to subinhibitory concentrations of a sequence-selective, DNA minor groove cross-linking pyrrolobenzodiazepine dimer.

Doyle Marie M Feuerbaum Eva-Anne EA Fox Keith R KR Hinds Jason J Thurston David E DE Taylor Peter W PW

The Journal of antimicrobial chemotherapy 20090910 5

<h4>Objectives</h4>ELB-21 is a pyrrolo[2,1-c][1,4]benzodiazepine dimer with potent antistaphylococcal activity; it binds covalently to guanine residues on opposing strands of duplex DNA, interfering with regulatory proteins and transcription elongation in a sequence-selective manner. Transcriptional and proteomic alterations induced by exposure of Staphylococcus aureus clinical isolate EMRSA-16 to ELB-21 were determined in order to define more precisely the bactericidal mechanism of the drug.<h4 ...[more]

PMID: 19744983

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Project description:Staphylococcus aureus (S. aureus) infections are notoriously complicated by the ability of the organism to grow in biofilms and are difficult to eradicate with antimicrobial therapy. The purpose of the current study was to clarify the influence of sub-inhibitory concentrations (sub-MICs) of daptomycin and tigecycline antibiotics on biofilm adhesion factors and exoproteins expressions by S. aureus clinical isolates. Six clinical isolates representing positive biofilm S. aureus clones (3 methicillin-sensitive S. aureus (MSSA) and 3 methicillin-resistant S. aureus (MRSA)) were grown with sub-MICs (0.5 MIC) of two antibiotics (daptomycin and tigecycline) for 12 h of incubation. RNA extracted from culture pellets was used via relative quantitative real-time-PCR (qRT-PCR) to determine expression of specific adhesion (fnbA, fnbB, clfA, clfB, fib, ebps, cna, eno) and biofilm (icaADBC) genes. To examine the effect of sub-MIC of these antibiotics on the expression of extracellular proteins, samples from the culture supernatants of six isolates were collected after 12 h of treatment with or without tigecycline in order to profile protein production via 2D gel sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D gel-SDS-PAGE). Sub-MIC treatment of all clinical MRSA and MSSA strains with daptomycin or tigecycline dramatically induced or suppressed fnbA, fnbB, clfA, clfB, fib, ebps, cna, eno, and icaADBC gene expression. Furthermore, sub-MIC use of tigecycline significantly reduced the total number of separated protein spots across all the isolates, as well as decreasing production of certain individual proteins. Collectively, this study showed very different responses in terms of both gene expression and protein secretion across the various isolates. In addition, our results suggest that sub-MIC usage of daptomycin and tigecycline could signal virulence induction by S. aureus via the regulation of biofilm adhesion factor genes and exoproteins. If translating findings to the clinical treatment of S. aureus, the therapeutic regimen should be adapted depending on antibiotic, the virulence factor and strain type.

Project description:BackgroundThe pathogenicity of staphylococcus aureus is dependent largely upon its ability to secrete a number of virulence factors, therefore, anti-virulence strategy to combat S. aureus-mediated infections is now gaining great interest. It is widely recognized that some plant essential oils could affect the production of staphylococcal exotoxins when used at subinhibitory concentrations. Perilla [Perilla frutescens (L.) Britton], a natural medicine found in eastern Asia, is primarily used as both a medicinal and culinary herb. Its essential oil (perilla oil) has been previously demonstrated to be active against S. aureus. However, there are no data on the influence of perilla oil on the production of S. aureus exotoxins.Methodology/principal findingsA broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) of perilla oil against S. aureus strains. Hemolysis, tumour necrosis factor (TNF) release, Western blot, and real-time RT-PCR assays were performed to evaluate the effects of subinhibitory concentrations of perilla oil on exotoxins production in S. aureus. The data presented here show that perilla oil dose-dependently decreased the production of α-toxin, enterotoxins A and B (the major staphylococcal enterotoxins), and toxic shock syndrome toxin 1 (TSST-1) in both methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA).Conclusions/significanceThe production of α-toxin, SEA, SEB, and TSST-1 in S. aureus was decreased by perilla oil. These data suggest that perilla oil may be useful for the treatment of S. aureus infections when used in combination with β-lactam antibiotics, which can increase exotoxins production by S. aureus at subinhibitory concentrations. Furthermore, perilla oil could be rationally applied in food systems as a novel food preservative both to inhibit the growth of S. aureus and to repress the production of exotoxins, particularly staphylococcal enterotoxins.

Dataset Information

Response of Staphylococcus aureus to subinhibitory concentrations of a sequence-selective, DNA minor groove cross-linking pyrrolobenzodiazepine dimer.

Publications

Response of Staphylococcus aureus to subinhibitory concentrations of a sequence-selective, DNA minor groove cross-linking pyrrolobenzodiazepine dimer.

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