Staphylococcus argenteus in Switzerland

Background Staphylococcus argenteus is a newly identified bacterial species belonging to the S. aureus complex. First characterized in Australia, it was later isolated all over the world. In our study we take a closer look at epidemiology, genetic background, resistance pattern and clinical presentation of S. argenteus in Switzerland. Methods We retrospectively re-typed 677 S. aureus isolates collected between August 2018 and Mai 2024 and stored in the biobank of the University Hospital of Zurich. Out of 677 isolates, six (0.89%) were identified as S. argenteus by MALDI-TOF. The sequence type (St) was determined by whole genome sequencing. Results Four isolates were St2250, the other two cases were identified as St1223. Resistance testing revealed that three isolates were pan-susceptible, two isolates were resistant against penicillin G and ampicillin, one isolate was resistant against penicillin G, ampicillin, and tetracycline. Five out of six isolates showed an invasive infection pattern and were the causative agent of the infection, while one strain was isolated from the nose of a patient suffering from a S. aureus invasive infection. Conclusion In conclusion, S. argenteus prevalence reflected the current situation found in Europe, Japan and South Korea and sequence types reflected the most prevalent ones found in the rest of the world. In line with the current guidelines, the antibiotic treatment mirrored the one used for S. aureus. It is however paramount to define prevalence, clinical presentations and pathogenicity of S. argenteus infections to be able to tailor specific treatment regimens in the