Enhanced resistance to erythromycin is conferred by the enterococcal msrC determinant in Staphylococcus aureus.
OBJECTIVE
The msrC gene, found on the chromosome of Enterococcus faecium, shares a high degree of similarity with the staphylococcal erythromycin resistance determinant msr(A). The enterococcal determinant was cloned into Staphylococcus aureus to determine whether msrC could confer antibiotic resistance in staphylococci.


METHODS
A shuttle vector comprising pBluescript and pSK265 was used to introduce multiple copies of msrC into S. aureus RN4220. The integration vector pCL84 was employed to insert a single copy of msrC into the S. aureus chromosome. MICs were determined by the broth microdilution method.


RESULTS
Expression of msrC from both chromosomal and plasmid loci in erythromycin-susceptible S. aureus RN4220 (MIC 0.25 mg/L) gave rise to enhanced protection against erythromycin, with an MIC of 32-64 mg/L for S. aureus RN4220 containing msrC in multiple copies and an MIC of 16-64 mg/L with msrC inserted as a single copy in the S. aureus chromosome.


CONCLUSIONS
MsrC mediates high-level resistance to erythromycin in S. aureus.
Reynolds
Elinor
E
School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, UK.
Cove
Jonathan H
JH
D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D024881:Drug Resistance, Bacterial / Q000187:drug effects / Q000235:genetics*; D016984:Enterococcus faecium / Q000187:drug effects* / Q000235:genetics; D004917:Erythromycin / Q000494:pharmacology*; D008969:Molecular Sequence Data; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics*
D001426:Bacterial Proteins; D004917:Erythromycin