| Summary: | <i>Staphylococcus epidermidis</i> has been recently recognized as an emerging nosocomial pathogen. There are concerns over the increasing virulence potential of this commensal due to the capabilities of transferring mobile genetic elements to <i>Staphylococcus aureus</i> through staphylococcal chromosomal cassette (SCC<i>mec</i>) and the closely related arginine catabolic mobile element (ACME) and the copper and mercury resistance island (COMER). The potential pathogenicity of <i>S. epidermidis</i>, particularly from blood stream infections, has been poorly investigated. In this study, 24 <i>S. epidermidis</i> isolated from blood stream infections from Oman were investigated using whole genome sequence analysis. Core genome phylogenetic trees revealed one third of the isolates belong to the multidrug resistance ST-2. Genomic analysis unraveled a common occurrence of SCC<i>mec</i> type IV and ACME element predominantly type I arranged in a composite island. The genetic composition of ACME was highly variable among isolates of same or different STs. The COMER-like island was absent in all of our isolates. Reduced copper susceptibility was observed among isolates of ST-2 and ACME type I, followed by ACME type V. In conclusion, in this work, we identify a prevalent occurrence of highly variable ACME elements in different hospital STs of <i>S. epidermidis</i> in Oman, thus strongly suggesting the hypothesis that ACME types evolved from closely related STs.
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