We have characterized a natural isolate of Staphylococcus epidermidis resistant to heavy metals that carries a small 2391-bp plasmid, pSepCH, encoding the qacC gene. The S. epidermidis qacC gene confers resistance to a number of β-lactam antibiotics and to ethidium bromide in its natural host and in Escherichia coli K12 and Salmonella enterica sv. Typhimurium. This is the first communication of a small multidrug resistance (SMR) pump involved in resistance to β-lactam antibiotics. Experiments using tolC, ompW and ompD mutant strains of S. Typhimurium demonstrated that the β-lactam antibiotic resistance conferred by this pump does not depend on these outer membrane proteins.
Bibliographical noteFunding Information:
The authors thank Le Phung and Simon Silver (University of Chicago) for helping with 16S rDNA sequencing. D.E.F. and J.M.P. received fellowships from MECESUP and C.A.N. and I.L.C. received fellowships from Conicyt. This work was supported by FONDECYT grants 1030234 to C.C.V. and 1020485 to G.C.M., and by NIH Fogarty Center Senior International Fellowship TW05645 to P.Y.
- Ethidium bromide
- Multidrug resistance
- Staphylococcus epidermidis
- β-Lactam resistance