Table 1.
Insights into β-lactam resistance development provided by WGS.
| mecA evolution |
| • mecA homologs are ubiquitous in S. fleurettii and S. vitulinus |
| •mecA homologue is present in the native location In S. fleurettii and S. vitulinus |
| • mecA and mecA2 in S. vitulinus do not provide resistance to β-lactams |
| •mecA homologs diversification begun with the use of antibiotics (1940s) |
| •rnecB and mecC were Identified |
| SCCmec evolution |
| •mec complex and SCC elements evolved in parallel in different chromosomal locations |
| • mecA homologs native location in S. sciuri species group is 200 Kb from orfX |
| •mecA and mecR2 originated from S. sciuri homologs |
| • mecRl/mecl were added to mecA to form the mec complex in S. fleurettii or S. vitulinus |
| • The last donors of J1 region and ccr to SCCmec were S. sciuri |
| • The last donors of mec complex, J2 and J3 regions to SCCmec were S. vitulinus/S. fleurettii |
| • Origin of SCC and SCCrnec is probably S. sciuri |
| •mecA was probably integrated into a SCC in 5. sciuri |
| • SCCmec III was probably the most ancient SCCmec type |
| Expression of β-lactam resistance |
| • Genetic basis of hetero-to-homo resistance conversion |
| – Tandem amplification of SCCmec |
| – Mutations in relA and rpoB |
| • Mechanisms of β-lactam resistance development in S. sciuri and S. vitulinus |
| – Alterations in mecAl/mecA2 promoter |
| – Alterations in PbpD structure |
| – SCCmec acquisition |