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| Status |
Public on Mar 12, 2013 |
| Title |
Comparison of the transcriptional profiles of intermediately vancomycin resistant and susceptible S. aureus strains |
| Platform organism |
Staphylococcus aureus subsp. aureus N315 |
| Sample organism |
Staphylococcus aureus |
| Experiment type |
Expression profiling by array
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| Summary |
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
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| Overall design |
For transcriptional profiling, the strains compared were grown in BHI to an optical density (600 nm) of 0.8-1.0. To guarantee statistical significance of the data, each experiment was replicated 4 times including a dye swap. RNA was isolated from two independent cultures of each strain. Each RNA preparation was used twice to synthesize cDNA resulting in four chips per competitive comparison.
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| Contributor(s) |
Jansen A, Sass P |
| Citation(s) |
23522028 |
| |
| Submission date |
Feb 14, 2008 |
| Last update date |
Jun 13, 2013 |
| Contact name |
Peter Sass |
| E-mail(s) |
[email protected]
|
| Organization name |
University of Bonn
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| Department |
Institute for Microbiology (IMMIP)
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| Street address |
Sigmund-Freud-Straße 25
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| City |
Bonn |
| State/province |
NRW |
| ZIP/Postal code |
53115 |
| Country |
Germany |
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| Platforms (2) |
| GPL5421 |
sciTracer Staphylococcus aureus N315 Scienion2005 |
| GPL5431 |
sciTracer_Staphylococcus_aureus_N315_Scienion2002 |
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| Samples (8)
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| Relations |
| BioProject |
PRJNA107881 |
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