Unknown,Transcriptomics,Genomics,Proteomics

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Metabolic and transcriptional activities of Staphylococcus aureus challenged with high-doses of daptomycin

ABSTRACT: Treatment of stationary growth phase Staphylococcus aureus SA113 with 100-fold of the MIC of the lipopeptide antibiotic daptomycin leaves alive a small fraction of drug tolerant albeit genetically susceptible bacteria. This study shows that cells of this subpopulation exhibit active metabolism even hours after the onset of the drug challenge. Isotopologue profiling using fully 13C-labeled glucose revealed de novo biosynthesis of the amino acids Ala, Asp, Glu, Ser, Gly and His. The isotopologue composition in Asp and Glu suggested an increased activity of the TCA cycle under daptomycin treatment compared to unaffected stationary growth phase cells. Microarray analysis showed differential expression of specific genes 10 minutes and 3 hours after addition of the drug. Besides factors involved in drug response, a number of metabolic genes appear to shape the signature of daptomycin-tolerant S. aureus cells. These observations will be useful towards the development of new strategies against persisters and related forms of bacterial cells with downshifted physiology. Altogether 12 samples were analysed. Bacteria were treated with Daptomycin and samples were taken 10 minutes (3 replicates) and 3 hours later (3 replicates). For each time-point untreated cultures were sampled as controls (3 replicates for each time-point).

ORGANISM(S): Staphylococcus aureus

SUBMITTER: Alexander Herbig

PROVIDER: E-GEOD-57908 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Objectives: Development of daptomycin resistance (DAPR) in Staphylococcus aureus is associated with clinical treatment failures. Mechanism(s) of such resistance has not been clearly defined. Methods: We studied an isogenic daptomycin-susceptible (DAPS) and daptomycin-resistant (DAPR) S. aureus strain pair (616; 701) from a patient with relapsing endocarditis during daptomycin treatment, using comparative transcriptomic and proteomic techniques. Results. Minor differences in genome content were found between strains by DNA hybridization. Transcriptomic analyses identified a number of genes differentially expressed in important functional categories: cell division, metabolism of bacterial envelopes and global regulation. Of note, the DAPR isolate exhibited reduced expression of the major cell wall autolysis gene coincident with upregulation of genes involved in wall teichoic acid production. Using quantitative (q)RT-PCR on gene cadre putatively involved in cationic peptide resistance, we formulated a putative regulatory network compatible with microarray data-sets, mainly implicating bacterial envelopes. Of interest, qRT-PCR of this same gene cadre from two distinct isogenic DAPS/DAPR clinical strain pairs revealed evidence of other strain dependent networks operative in the DAPR phenotype. Comparative proteomics of 616 vs 701 revealed differential abundance of proteins in various functional categories including: cell-wall associated targets and biofilm-formation proteins. Phenotypically, strains 616 and 701 showed major differences in ability to develop bacterial biofilms in presence of the antibacterial lipid, oleic acid. Conclusions: Compatible with previous in vitro observations, in vivo acquired DAPR in S. aureus is a complex, multistep phenomenon allowing for: i) strain dependent phenotypes; ii) transcriptome adaptation; and iii) modification of lipid and protein content of cellular envelopes. Daptomycin suceptible strain vs daptomycin non suceptible strain after daptomycin treatment

Project description:Several groups have shown that through evolution experiments, tolerance evolved rapidly under cyclic antibiotic treatment which then promote the emergence of resistance. In other words, intermittent antibiotic exposure will “train” the bacteria to become tolerant to the drug, and then boost the chances for them to become fully resistant. This evolutionary trajectory of evolving tolerance and resistance not only occurs in vitro, but also in clinical patients with MRSA blood infections. Despite the fact that repetitive antibiotic treatment will lead to tolerance and resistance development in bacterial populations, the difference on the evolutionary path between those treated with a single drug and drug combination remains unaddressed. In this study, we monitored the development of tolerance in MRSA by treating them with either daptomycin alone for 2 weeks (Scheme 1), or daptomycin combined with rifampin for two weeks (Scheme 2), in a cyclic manner. In addition, we also investigate another scenario where we treat MRSA cells with daptomycin alone for one week, and subsequently treat them with daptomycin and rifampin combination in the second week (Scheme 3). At the end of the evolution experiment, we observed that the population from Scheme 1 developed tolerance towards daptomycin, the population from Scheme 2 developed both tolerance and resistance towards daptomycin, while the population from Scheme 3 developed tolerance after a week of treatment, but then the tolerance phenotype diminished at the end of the second week due to the drug combination treatment. We subjected them to whole genome sequencing and identified single point mutations that are responsible for the observed phenotype. Through proteomics, we compared the proteome profile of the population evolved from scheme 1 (S1D14), scheme 2 (S2D14) and scheme 3 (S3D14), and we observed that these three populations employ distinct mechanisms to survive antibiotic treatment, suggesting that the treatment strategy for these populations should be tailored depending on the treatment conditions.

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Metabolic and transcriptional activities of Staphylococcus aureus challenged with high-doses of daptomycin

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