Increased in vitro phenol-soluble modulin production is associated with soft tissue infection source in clinical isolates of methicillin-susceptible Staphylococcus aureus

Summary Background Phenol-soluble modulins (PSM) are amphipathic proteins produced by Staphylococcus aureus that promote virulence, inflammatory response, and biofilm formation. We previously showed that MRSA isolates from soft tissue infection (SSTI) produced significantly higher levels of PSM than MRSA isolates from hospital-acquired pneumonia (HAP) or infective endocarditis (IE). In this investigation, we sought to validate this finding in methicillin-susceptible S. aureus (MSSA) isolates. Methods MSSA isolates (n = 162) from patients with SSTI, HAP, and IE were matched 1:1:1 based on geographic origin of the infection to form 54 triplets (North America n = 27, Europe n = 25, Australia n = 2). All isolates underwent spa typing and were classified using eGenomics. In vitro PSM production was quantified by high-performance liquid chromatography/mass spectrometry. Fischer's Exact Test and the Kruskal–Wallis test were used for statistical analysis. Results Spa 1 was more common in SSTI (14.81% SSTI, 3.70% HAP, 1.85% IE) (p  Spa 2 was more common in HAP (0% SSTI, 12.96% HAP, 3.70% IE) (p  Spa 1 isolates produced significantly more delta-toxin (p  Spa 1 isolates. No associations between PSM levels and clinical outcome of SSTI, HAP, or IE were identified. Conclusion Production of PSMα1-4 is highest in SSTI MSSA isolates, supporting the hypothesis that these peptides are important for SSTI pathogenesis. These findings are similar to those described in MRSA, and demonstrate that associations between PSM levels and type of infection are independent of the methicillin-resistance status of the isolate.