Natural human isolates of Staphylococcus aureus selected for high production of proteases and alpha-hemolysin are sigmaB deficient.

It has been reported that high production of proteases and alpha-hemolysin in the prototype Staphylococcus aureus strain 8325-4 was associated with its sigmaB deficiency. Here we analyzed one fresh clinical isolate (KS26) and two ancient human isolates (Wood46 and V8) selected for high production of proteases and alpha-hemolysin. All three strains lacked yellow pigment and showed a low level of expression of sigB-dependent promoters, indicating sigmaB deficiency.