SGPL1 and bacterial infectious disease: The spl operon is encoded on the νSaβ pathogenicity island alongside with other known S. aureus virulence factors, suggesting an important role during bacterial infection.[6,7] The operon is composed of six genes encoding the proteases SplA to SplF.[8,9] The spl genes are found in the majority of S. aureus strains, but the composition of the spl operon varies.