A Potentially Misleading Name: Staphylococcus argenteus in an Urosepsis: A Case Report.

Staphylococcus argenteus, a recently recognized species within the Staphylococcus aureus complex, shares numerous virulence traits with S. aureus. While S. argenteus typically lacks pigmentation and exhibits greater antibiotic susceptibility compared to S. aureus, it can cause severe infections, including bacteremia. Clinicians can be misled by its name and may not give it the necessary attention. It may also be misidentified as a S. aureus by the microbiology lab. We present the case of a 56-year-old man with a complex medical history who developed a polymicrobial urosepsis involving S. argenteus. It was initially misinterpreted as a contaminant in urinary samples by an external laboratory. The patient subsequently developed septic shock and was admitted to intensive care unit. The blood cultures confirmed S. argenteus associated with E. coli and K. pneumoniae bacteremia. He was successfully treated with high-dose intravenous floxacillin and oral ciprofloxacin. Whole-genome sequencing confirmed the isolate as S. argenteus (ST2250). This case underscores the diagnostic and clinical challenges posed by S. argenteus, particularly in regions where its prevalence is low. S. argenteus harbors the majority of S. aureus virulence genes and causes a comparable spectrum of disease. Epidemiological data indicate regional differences in its prevalence and clinical impact. Some studies report lower virulence while others suggest worse outcomes. The case illustrates the importance of accurate identification using techniques like MALDI-TOF MS and whole-genome sequencing. Clinicians and microbiologists should remain vigilant and consider S. argenteus as a pathogen, warranting appropriate antimicrobial therapy and clinical attention. Differentiating it from S. aureus might be relevant for guiding therapy, surveillance, and infection control, particularly given emerging reports of methicillin-resistant S. argenteus strains.