Komplexní analýza genomů jedinečných bakteriofágů a plazmidů nesoucích geny pro exfoliativní toxiny A a B u Staphylococcus aureus
| Title in English | Complex genome analysis of unique bacteriophages and plasmids carrying genes for exfoliative toxins A and B in Staphylococcus aureus |
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| Authors | |
| Year of publication | 2017 |
| Type | Article in Periodical |
| Magazine / Source | Informační listy |
| MU Faculty or unit | |
| Citation | |
| web | http://www.gsgm.cz/files/il_gsgm_50_2017.pdf |
| Keywords | exfoliative toxins; ETA phages; ETB plasmids; Staphylococcus aureus |
| Description | Staphylococcus aureus is an important opportunistic pathogen and common cause of bacterial nosocomial infections. A horizontal gene transfer of virulence factors, promoted by tempered bacteriophages and plasmids, plays a crucial role in mechanism of pathogenic strains origin. Exfoliative toxins A (ETA) and B (ETB), transferred by this way, are the cause of epidermolytic diseases mostly of newborns and young children. The mild localized form is called bullous impetigo, while the generalized life-threatening condition is known as staphylococcal scalded skin syndrome (SSSS). This dissertation is focused on molecular characterization and comparative genomic analysis of previously undescribed staphylococcal eta-positive bacteriophages of the family Siphoviridae (ETA phages) and etb-positive plasmids (ETB plasmids) isolated from S. aureus strains implicated in epidermolytic diseases in Czech Republic. The strains containing studied ETA phages and ETB plasmids were chosen on the base of etiology, clinical source and genotyping. The DNA of isolated phages and plasmids was sequenced and annotated. Analysis of the ETA phage genomes revealed numerous differences that manifested, for example, in virion structural proteins. Several parts gained probably by recombination were identified. So, both the phages represent novel and up to now undescribed types of phages belonging to Siphoviridae family. Using them, we accomplished positive lysogenic conversion of non-toxigenic S. aureus strain to highly effective producer of ETA. This confirmed an important impact of ETA phages on the host strain pathogenicity. The analysis of ETB plasmids showed, that plasmids isolated from S. aureus strains of clonal complex CC121 share a large part of DNA sequence including typical virulence genes, i.e. genes for ETB and EDIN C. However, plasmids of this lineage contain also variable regions facilitating their differentiation. Although ETB plasmids have been assumed to be relatively uniform, we unexpectedly isolated and described a novel yet unknown type showing minimal sequence homology with other ETB plasmids. Moreover, it carries genes for conjugation and novel variants of virulence genes including etb. Therefore, it represents a novel lineage of ETB plasmids. A valuable multiplex PCR assay has been designed to distinguish all the types of ETB plasmids. The last part of this thesis is focused on gene typing of S. aureus strains isolated from 92 Czech patients suffered for cystic fibrosis. While more than half of isolates was enterotoxin genes-positive, only two of them contain eta gene. No etb gene-positive isolate was detected. These results correspond to previously published low prevalence of exfoliative toxin-producing strains. |
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