Structural changes induced by mupirocin in Staphylococcus aureus cells

Cells of mupirocin-sensitive, moderately-resistant and highly-resistant cul tures of Staphylococcus aureus (mupirocin MICs 0.13, 16 and > 512 mg/l, res pectively) were exposed to various concentrations of the antibiotic and exa mined by transmission electron microscopy. The most severe damage occurred in mupirocin-sensitive cells. Cells from moderately-resistant cultures trai ned in vitro to high-level mupirocin resistance were more hydrophobic than the parent cells. The antibiotic was slowly lethal to the mupirocin-sensiti ve strain and sub-inhibitory concentrations prevented or reduced growth of the other strains over a 6 h incubation period, irrespective of whether the drug was added at zero time or in the exponential growth phase. (C) 1999 E lsevier Science B.V. and International Society of Chemotherapy. All rights reserved.