Genomic analysis of food-borne staphylococcus aureuscc30 strains in the russian federation

Staphylococcus aureus clonal complex (СС) 30 are associated with hospital-acquired and community-associated invasive infections and may cause outbreaks of staphylococcal food-borne infections (SFI). In recent years, severe SFI outbreaks caused by S. aureus CC30 in cohorts not linked to high-risk groups have been detected in Russia. Aim: The aim of the study is to conduct a comparative genomic analysis of S. aureus strains B-7778 and B-7779 isolated during widespread SFI outbreak at the International Youth Forum Seliger in 2014, and S. aureus strains B-7738 and B-7739 isolated during widespread SFI outbreak among construction personnel in Saint Petersburg in 2013. Methods: Seliger-2014 S. aureus cultures were screened by PCR and sequence typing. S. aureus strains B-7778 and B-7779 were isolated from clinic material and from food handlers, respectively. Draft genome sequencing and phylogenetic analysis of S. aureus strains B-7778 and B-7779 were carried out. The production of enterotoxin A was determined by the enzyme immunoassay. Results: S. aureus strain B-7778 isolated from 38 patients and S. aureus strain B-7779 isolated from two food handlers at the Forum Seliger-2014 have identical nucleotide sequences, belong to spa-type t122 and sequence-type 30, and carry a set of toxin genes being responsible for SFI manifestations. The core-genome SNP typing has shown that S. aureus B-7738/ B-7739 (St. Petersburg, 2013) and S. aureus B-7778/ B-7779 (Seliger, 2014) belong to different clusters of S. aureus СС30 clade 3. S. aureus B-7778/ B-7779 not closely related with major clusters of S. aureus СС30. The production of enterotoxin A, SFI etiological factor, by S. aureus strains B-7738, B-7739, B-7778, and B-7779 has been confirmed. Conclusion: The genomic analysis of SFI-associated S. aureus strains isolated in Russia has been conducted for the first time. Two different genetic clones of S. aureus СС30 which are able to cause severe SFI outbreaks in cohorts not linked to high-risk groups have been identified and characterized. SNP typing of Seliger-2014 S. aureus genomes has revealed their genetic specificity among known strains of S. aureus CC30. Identified genome sequences of SFI-associated strains will be used for further studies S. aureus clones circulating through the food chain in Russia.