A clone of the emergent Streptococcus pyogenes emm89 clade responsible for a large outbreak in a post-surgery oncology unit in France
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An outbreak of nosocomial infections due to Streptococcus pyogenes (Group A Streptococcus; GAS) occurred in a post-surgery oncology unit and concerned more than 60 patients and lasted 20 months despite enhanced infection control and prophylaxis measures. All GAS strains were characterized (emm genotype, toxin gene profile and pulse-field gel electrophoresis subtype). Selected strains were sequenced and phylogenetic relationship established. Capacity to form biofilm and interaction with human pulmonary epithelial cells and macrophages were determined. Twenty-six GAS strains responsible for invasive infections (II) and 57 for non-II or colonization were isolated from patients (n = 66) or healthcare workers (n = 13). Seventy strains shared the same molecular markers and 69 the same PFGE pattern; 56 were sequenced. They all belonged to the emerging emm89 clade 3; all but 1 were clonal. Whole genome sequencing identified 43 genetic profiles with sporadic mutations in regulatory genes and acquired mutations in 2 structural genes. Except for two regulatory gene mutants, all strains tested had the same biofilm formation capacity and displayed similar adherence and invasion of pulmonary epithelial cells and phagocytosis and survival in human macrophages. This large outbreak of GAS infection in a post-surgery oncology unit, a setting that contains highly susceptible patients, arose from a strain of the emergent emm89 clade. No relationship between punctual or acquired mutations, invasive status, and strain phenotypic characteristics was found. Noteworthy, the phenotypic characteristics of this clone account for its emergence and its remarkable capacity to elicit outbreaks.
KeywordsGroup A Streptococcus emm89 Emerging clade Phylogeny Biofilm Bacterium–cell interaction Outbreak
This work was supported by Santé Publique France, INSERM, CNRS, Université Paris Descartes and by the High Council for Scientific and Technological Cooperation between France-Israel “Complexity in Biology” program.
Conceived and designed the study: Céline Plainvert, Agnès Fouet, and Claire Poyart. Provided clinical and epidemiological data Elise Seringe, Eric Hernandez, and Pascal Astagneau. Performed the bacteriological analyses Magalie Longo, Nicolas Dmytruk, and Gislaine Collobert. Performed biofilms and phagocytosis analyses Magalie Longo. Performed whole genome sequencing of bacterial strains Benjamin Saintpierre, Elisabeth Sauvage, Laurence Ma and Johann Beghain. Analyzed genomes data Philippe Glaser, Frédéric Ariey, and Agnès Fouet. Wrote the manuscript Claire Poyart, Céline Plainvert, and Agnès Fouet.
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Conflict of interest
The other authors declare no competing financial interests.
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