High mortality impact of Staphylococcus argenteus on patients with community-onset staphylococcal bacteraemia

Staphylococcus argenteus is increasingly reported. Evaluating the impact of S. argenteus infection on patient outcomes for future therapeutic and infection control decision-making is imperative. A retrospective study was conducted to investigate the prevalence of S. argenteus bacteraemia at a Taiwanese medical centre between 2010-2012. Staphylococcus argenteus was identified based on absence of the crtM gene and multilocus sequence typing (MLST) analysis. Clinical characteristics between S. argenteus and Staphylococcus aureus bacteraemia were compared. The independent effect of S. argenteus on bacteraemia mortality was evaluated. A total of 47 S. argenteus isolates were re-identified from 394 S. aureus bacteraemia isolates. All S. argenteus isolates were susceptible to methicillin and multiple other antibiotics. Most of the S. argenteus isolates (36/47; 76.6%) were sequence type 2550 (ST2550). Comparing the 47 S. argenteus bacteraemia cases with 232 methicillin-susceptible S. aureus (MSSA) bacteraemia cases, S. argenteus bacteraemia patients had significantly higher percentages of polymicrobial infection, recent hospitalisation in the past 3 months, thrombocytopenia, lower respiratory tract infection and short-term mortality. Compared with MSSA bacteraemia, S. argenteus bacteraemia was independently associated with an increased risk of mortality [adjusted hazard ratio (aHR) = 1.845, 95% confidence interval (CI) 1.033-3.294] using multivariate Cox regression analysis. In a stratified analysis, S. argenteus bacteraemia was associated with a higher mortality risk than MSSA bacteraemia among patients with prior healthcare-associated exposure (aHR = 2.769, 95% CI 1.489-5.149). Although more susceptible to multiple antibiotics, S. argenteus bacteraemia cases were independently associated with higher mortality than MSSA bacteraemia cases.