Comparative Genomic Analysis of Staphylococcal Cassette Chromosome Type V Strains and Estimation of the Emergence of SCC V Clinical Isolates in Korea.

BACKGROUND

Staphylococcal cassette chromosome type V (SCC V) methicillin-resistant (MRSA) has been recovered from patients and livestock. Using comparative genomic analyses, we evaluated the phylogenetic emergence of SCC V after transmission from overseas donor strains to Korean recipient strains.

METHODS

Sixty-three complete MRSA SCC V genomes (including six Korean clinical isolates) were used to construct a phylogenetic tree. Single-nucleotide polymorphisms were identified using Snippy, and a maximum-likelihood-based phylogenetic tree was constructed using RAxML. The possible emergence of the most common ancestor was estimated using BactDating. To estimate horizontal gene transfer (HGT) events, Ranger-dtl was applied to 818 SCC V strains using publicly available whole-genome data.

RESULTS

The phylogenetic tree showed five major clades. German strains formed a major clade; their possible origin was traced to the 1980s. The emergence of Korean SCC V clinical isolates was traced to 2000-2010. HGT events in spp. were identified in seven strains. P7 (Hong Kong outbreak strain) served as the donor strain for two Korean sequence type (ST) 59 strains, whereas the other five recipient strains emerged from different SCC V donors.

CONCLUSIONS

Most Korean SCC V strains may have emerged during 2000-2010. A unique MRSA SCC V strain, ST72 (a Korean common type of community-associated MRSA), was also identified. The genomic dynamics of this clone with a zoonotic background should be monitored to accurately understand MRSA evolution.