The antimicrobial activity of mupirocin--an update on resistance.

Mupirocin (pseudomonic acid A) has a novel chemical structure that is unrelated to any other known class of antibiotic, and possesses a unique mode of action. As a consequence, mupirocin lacks cross-resistance with other antibacterial agents and exhibits activity against strains of bacteria that are multiresistant. The selection in vitro of resistant variants of Staphylococcus aureus is slow, which is reflected in the low incidence of mupirocin resistance encountered in clinical practice. Pulse field gel electrophoresis studies on S. aureus highly resistant to mupirocin, have confirmed the presence of a large plasmid in the majority, but not all, of the isolates. Restriction endonuclease digests of the large plasmid DNA, and DNA hybridization studies with a non-radiolabelled probe constructed from total plasmid DNA, have shown that there were marked differences in plasmid types between isolates from different locations, but general similarities between plasmid types isolated from the same location.