Metabolome of three Vancomycin-intermediate Staphylococcus aureus (VISA) mutants compared with the parent strain MM66
Ontology highlight
ABSTRACT:
ORGANISM(S): S. Aureus Staphylococcus Aureus
TISSUE(S): Bacterial Cells
DISEASE(S): Antibiotic Resistance
SUBMITTER: 
John Gustafson
PROVIDER: ST000309 | MetabolomicsWorkbench | Tue Jan 12 00:00:00 GMT 2016
REPOSITORIES: MetabolomicsWorkbench
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Project description:The phenotype “intermediate vancomycin resistance” in Staphylococcus aureus (CLSI: MIC = 4-8 mg/L) has been assigned to changes that lead to alterations in cell wall synthesis and morphology. Most vancomycin intermediately resistant S. aureus (VISA) strains are characterised by an increased cell wall thickness as a consequence of an activated cell wall biosynthesis and decreased autolysis. The purpose of this study was to analyse the genetic basis of the vancomycin resistance mechanism of the clinical VISA isolate SA137/93A and its spontaneous mutant strain SA137/93G. The methicillin-resistant S. aureus (MRSA) SA137/93A was isolated from a tracheal secretion and displays heterogeneous intermediate vancomycin resistance (hVISA strain, MIC: 8 mg/L in BHI). Subculturing in presence of 6 mg/L vancomycin generated a mutant with homogeneous intermediate vancomycin resistance, that showed an MIC value of 16 mg/L in BHI and was designated SA137/93G. PFGE profiles and phage typing of the strains showed that they were members of the Iberian clone (ST247), which was prevalent in Germany in the early nineties under the designation “Northern German epidemic strain”. Both strains possess a thickened cell wall. However, the vancomycin resistance of strain SA137/93A is most probably enhanced by an increased amount of free D-Ala-D-Ala termini in the cell wall, which is due to decreased crosslinking, whereas the mutant strain SA137/93G shows normal crosslinking. Moreover, strain SA137/93A displays an increased expression of the essential two-component system yycFGHI as a consequence of an IS256 insertion in the promoter region, while strain SA137/93G is characterised by an insertion of IS256 into the gene tcaA. Although both insertions were shown to correlate with a decrease in susceptibility to vancomycin, the difference in the vancomycin resistance level of the strain pair could be mainly attributed to the disruption of tcaA in the mutant.This study was conducted to identify resistance mechanisms that both strains might have in common. To this end we compared the transcriptomes of both strains with that of the closely related vancomycin susceptible MRSA/VSSA strain SA1450/94 (MIC: 2 mg/L). We found that the genes of the capsule biosynthesis were the only genes with higher expression in both VISA strains. Keywords: strain comparison
2013-03-12 | GSE10529 | GEO
Project description:Complete reconstitution of the vancomycin-intermediate Staphylococcus aureus (VISA) phenotype of Mu50 was achieved by sequentially introducing mutations into five genes of a vancomycin-susceptible S. aureus (VSSA) strain ∆IP. Introduction of mutation Ser329Leu into vraS encoding the sensor histidine kinase of vraSR two-component regulatory (TCR) system and another mutation Glu146Lys into msrR, encoding putative methionine sulfoxide reductase regulator, raised vancomycin resistance to the level of heterogeneously vancomycin-intermediate S. aureus (hVISA) strain Mu3. Introduction of two more mutations, graR (Asn197Ser) of graSR TCR system and rpoB(His481Tyr) encoding ß subunit of RNA polymerase, converted the hVISA strain into a VISA strain having the level of vancomycin resistance of Mu50. Surprisingly, however, the constructed quadruple mutant strain did not have thickened cell wall, a cardinal feature of VISA phenotype. Subsequent study showed that cell-wall thickening was an inducible phenotype with the mutant strain as opposed to that of Mu50, which is a constitutive one. Finally, introduction of mutation Ala297Val into the orf SAV2309 of the mutant strain converted the inducible cell-wall thickening into a constitutive one. SAV2309 encodes a putative formate dehydrogenase (designated Fdh2). Though not a transcription regulator, the mutation of the fdh2 caused a significant change in transcriptome. Thus, all of the five mutated genes required for VISA phenotype acquisition were directly or indirectly involved in the regulation of cell physiology. VISA seemed to be achieved through multiple genetic events accompanying drastic changes in cell physiology.
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Project description:Staphylococcus aureus is a notorious bacterial pathogen that causes a broad range of human diseases, and isolates that are resistant to several antibiotic classes including last resort antibiotics like vancomycin and daptomycin complicate the situation. We characterized S. aureus VC40, a strain that shows full resistance to vancomycin (MIC of 64 M-BM-5g/ml) and daptomycin (MIC of 4 M-BM-5g/ml) as well as a decreased susceptibility to further cell wall active agents. Genome sequencing revealed mutations in genes encoding the histidine kinases WalK and VraS that control cell envelope related processes and gene expression profiling indicated the induction of the respective regulons in strain VC40. Reconstitution of the mutations in walK or vraS into the susceptible S. aureus NCTC 8325 background resulted in a considerably increased resistance to vancomycin and daptomycin with MICs surpassing the clinical breakpoints for these antibiotics, thereby generating vancomycin-intermediate S. aureus (VISA) strains. As observed for S. aureus VC40, the walKwalk and vraS mutations also led to an increased expression of the respective regulons in the NCTC 8325 background. Phenotypic studies showed that S. aureus VC40 as well as the walKwalk and vraS mutants of strain NCTC 8325 were characterized by a significantly thickened cell wall, a decreased growth rate, a reduced autolytic activity and an increased resistance to lysostaphin-induced lysis. These results demonstrate that the WalK and VraS histidine kinases act as major switches which allow S. aureus to rapidly develop vancomycin resistance up to the VISA level via mutation of one single gene locus and concomitantly contribute to cross-resistance to other antibiotics including the last resort antibiotic daptomycin. Microarray was used to evaluate alteration in the transcriptome of mutS mutant and compared to the parental strain VC40
2014-08-18 | E-GEOD-46887 | biostudies-arrayexpress
Project description:Staphylococcus aureus is a notorious bacterial pathogen that causes a broad range of human diseases, and isolates that are resistant to several antibiotic classes including last resort antibiotics like vancomycin and daptomycin complicate the situation. We characterized S. aureus VC40, a strain that shows full resistance to vancomycin (MIC of 64 µg/ml) and daptomycin (MIC of 4 µg/ml) as well as a decreased susceptibility to further cell wall active agents. Genome sequencing revealed mutations in genes encoding the histidine kinases WalK and VraS that control cell envelope related processes and gene expression profiling indicated the induction of the respective regulons in strain VC40. Reconstitution of the mutations in walK or vraS into the susceptible S. aureus NCTC 8325 background resulted in a considerably increased resistance to vancomycin and daptomycin with MICs surpassing the clinical breakpoints for these antibiotics, thereby generating vancomycin-intermediate S. aureus (VISA) strains. As observed for S. aureus VC40, the walKwalk and vraS mutations also led to an increased expression of the respective regulons in the NCTC 8325 background. Phenotypic studies showed that S. aureus VC40 as well as the walKwalk and vraS mutants of strain NCTC 8325 were characterized by a significantly thickened cell wall, a decreased growth rate, a reduced autolytic activity and an increased resistance to lysostaphin-induced lysis. These results demonstrate that the WalK and VraS histidine kinases act as major switches which allow S. aureus to rapidly develop vancomycin resistance up to the VISA level via mutation of one single gene locus and concomitantly contribute to cross-resistance to other antibiotics including the last resort antibiotic daptomycin.
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Project description:WalKR is an essential two component regulatory system in S. aureus, thought to control cell wall metabolism. Using genome sequencing of 5 paired clinical isolates of vancomycin-susceptible and vancomycin-intermediate S. aureus we found frequent, but unique, mutations in this locus. To investigate the contribution of these mutations to vancomycin resistance allelic replacement WalK (G223D) and WalR (K208R) mutants were generated and compared to the parent strains. Mutations in walk and walR led to increased vancomycin resistance, reduced biofilms formation and attenuation of virulence, demonstrating that minor genetic changes in this locus can lead to significant changes in bacterial resistance and virulence. Microarray transcriptional comparisons were performed to investigate the regulatory effects of the WalK (G223D) and WalR (K208R) mutations, and demonstrated that while changes in genes affecting cell wall metabolism were detected, more dramatic changes were found in regulation of cellular metabolism. Transcriptional profiling of laboratory derived S. aureus walKR mutants compared to the parent isolates. TPS3130 has a single point mutation in walK, and TPS3190 has a single point mutation in walR. Two condition experiment TPS3130 vs JKD6009 and TPS3190 vs JKD6004. 3 biological replicates per isolate pair, one replicate per slide.
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Project description:The mechanisms leading to the vancomycin-intermediate Staphylococcus aureus (VISA) phenotype are incompletely understood. In an effort to identify VISA determinants, clinical hVISA strain MM66 and its 1st-step VISA mutants were compared. S. aureus microarrays, array data analysis protocols (NIAID's Pathogen Functional Genomics Resource Center), as well as comparative genomic sequencing (CGS) were utilized to determine VISA transcriptome alterations and mutations that define the MM66 VISA mechanism. In addition, whole cell autolysis, antimicrobial susceptibility tests, growth in the presence of salt, coagulase and hemolysis assays were performed to confirm VISA transcriptional alterations. Overall, 2 MM66 VISA demonstrated 85 up-regulated and 8 down-regulated genes in common. SAMMD (Staphylococcus aureus Microarray Metadatabase) analysis identified a significant differential gene expression overlap between the global stress response regulator sigB-controlled genes in MM66-3 and MM66-4. CGS analysis on a MM66 VISA revealed two mutations in: a sensory box histidine kinase (yycG) and a putative adenine phosphoribosyltransferase (apt). The yycFG two-component system has been reported to regulate whole cell autolysis and MM66 VISA demonstrated reduced whole cell autolysis. Five ssaA homologues (putative amidases) and a gene that expresses a bifunctional autolysin (atlA) controlled by YycFG were downregulated in MM66 VISA. One MM66 VISA mutant demonstrated drastic downregulation of a gene cluster (betA, gbsA, betB, and cudT) required for the osmoprotective response of S. aureus and MM66 VISA mutants demonstrated reduced growth in high salt media compared to MM66. Virulence genes were also downregulated (coa, hla, hlb, hlgA, hlgB, and hlgC) in 2 MM66 VISA mutants which also demonstrated reduced coagulase and hemolytic activities compared to MM66. pur operon genes were also upregulated in MM66 VISA and it is interesting that we have also found an apt mutation, since Apt activity can be inhibited by high AMP levels and reduces the conversion of AMP into adenine. Conclusion: Mutations in yycG and apt allow hVISA to acquire the VISA phenotype and yycFG is involved with altered autolytic activity in MM66 VISA.
2010-03-25 | GSE16479 | GEO
Project description:To determine if significant genomic changes are associated with the development of vancomycin intermediate Staphylococcus aureus, genomic DNA microarrays were performed to compare the initial vancomycin susceptible Staphylococcus aureus (VSSA) and a related vancomycin intermediate Staphylococcus aureus (VISA) isolate from five unique patients (five isolate pairs). Keywords: comparative genomic hybridization
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