Which methods are appropriate for the detection of Staphylococcus argenteus and is it worthwhile to distinguish S. argenteus from S. aureus?

Which methods are appropriate for the detection of Staphylococcus argenteus and is it worth to distinguish S. argenteus from S. aureus? René Kaden,1 Lars Engstrand,2 Hilpi Rautelin,1 Cecilia Johansson1 1Department of Medical Sciences, Clinical Microbiology, Uppsala University, Uppsala, Sweden; 2Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Solna, Sweden Purpose: To further analyze a clinical isolate originally identified as methicillin-resistant Staphylococcus aureus (MRSA) using whole-genome sequencing and comparative genomics.Materials and methods: Classical diagnostic methods such as cultivation, biochemical tests, and PCR were supplemented with whole-genome sequencing and comparative genomics, to identify the isolate.Results: The isolate was phenotypically similar to MRSA. However, the presence of the nuc gene could not be confirmed using PCR, while it was positive for the mecA gene. Whole-genome sequencing correctly identified the isolate as Staphylococcus argenteus. The isolate possessed several resistance genes, such as mecA, blaZ (β-lactam antibiotics) and dfrG (trimethoprim). The nuc gene differed from that of MRSA. Six phylogenetic distinct clusters were identified by average nucleotide identity (ANI) analysis of all available S. argenteus whole-genome sequences. Our isolate, RK308, clustered with those isolated in Europe and Asia.Conclusion: Due to the invasive potential, the multi-drug resistance and the similarity to MRSA, S. argenteus should be included in the MRSA screening. Due to the divergent genome compared to MRSA, new PCR approaches have to be developed to avoid an unnoticed spreading of S. argenteus. Keywords: Staphylococcus argenteus, Staphylococcus aureus, MRSA, whole-genome sequencing, clinical diagnostics