Altered growth, pigmentation, and antimicrobial susceptibility properties of Staphylococcus aureus due to loss of the major cold shock gene cspB.

An insertional mutation made in the major cold shock gene cspB in Staphylococcus aureus strain COL, a methicillin-resistant clinical isolate, yielded a mutant that displayed a reduced capacity to respond to cold shock and many phenotypic characteristics of S. aureus small-colony variants: a growth defect at 37 degrees C, a reduction in pigmentation, and altered levels of susceptibility to many antimicrobials. In particular, a cspB null mutant displayed increased resistance to aminoglycosides, trimethoprim-sulfamethoxazole, and paraquat and increased susceptibility to daptomycin, teicoplanin, and methicillin. With the exception of the increased susceptibility to methicillin, which was due to a complete loss of the type I staphylococcal cassette chromosome mec element, these properties were restored to wild-type levels by complementation when cspB was expressed in trans. Taken together, our results link a stress response protein (CspB) of S. aureus to important phenotypic properties that include resistance to certain antimicrobials.