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Characterization of Streptococcus tigurinus small-colony variants causing prosthetic joint infection by comparative whole-genome analyses

Zbinden, Andrea
Quiblier, Chantal
Herzog, Kathrin
Bodler, Paul
Senn, Maria M
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Published in Journal of clinical microbiology. 2014, vol. 52, no. 2, p. 467-74
Abstract Small-colony variants (SCVs) of bacteria are associated with recurrent and persistent infections. We describe for the first time SCVs of Streptococcus tigurinus in a patient with a prosthetic joint infection. S. tigurinus is a novel pathogen of the Streptococcus mitis group and causes invasive infections. We sought to characterize S. tigurinus SCVs using experimental methods and find possible genetic explanations for their phenotypes. The S. tigurinus SCVs were compared with the wild-type (WT) isolate using phenotypic methods, including growth under different conditions, autolysis, and visualization of the cell ultrastructure by use of transmission electron microscopy (TEM). Furthermore, comparative genome analyses were performed. The S. tigurinus SCVs displayed reduced growth compared to the WT and showed either a very stable or a fluctuating SCV phenotype. TEM analyses revealed major alterations in cell separation and morphological abnormalities, which were partially explained by impaired autolytic behavior. Intriguingly, the SCVs were more resistant to induced autolysis. Whole-genome sequencing revealed mutations in the genes involved in general cell metabolism, cell division, stringent response, and virulence. Clinically, the patient recovered after a 2-stage exchange of the prosthesis. Comparative whole-genome sequencing in clinical strains is a useful tool for identifying novel genetic signatures leading to the most persistent bacterial forms. The detection of viridans streptococcal SCVs is challenging in a clinical laboratory due to the small colony size. Thus, it is of major clinical importance for microbiologists and clinicians to be aware of viridans streptococcal SCVs, such as those of S. tigurinus, which lead to difficult-to-treat infections.
Keywords Aged, 80 and overArthritis/microbiologyDNA Mutational AnalysisDNA, Bacterial/chemistry/geneticsFemaleGenome, BacterialHumansMicroscopy, Electron, TransmissionMolecular Sequence DataMutationProsthesis-Related Infections/microbiologySequence Analysis, DNAStreptococcal Infections/microbiologyStreptococcus/genetics/growth & development/isolation & purification/ultrastructure
PMID: 24478475
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Research group Analyse génomique et fonctionnelle du staphylocoque doré (604)
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ZBINDEN, Andrea et al. Characterization of Streptococcus tigurinus small-colony variants causing prosthetic joint infection by comparative whole-genome analyses. In: Journal of clinical microbiology, 2014, vol. 52, n° 2, p. 467-74. doi: 10.1128/JCM.02801-13 https://archive-ouverte.unige.ch/unige:74108

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Deposited on : 2015-07-14

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