In vivo transfer of high-level mupirocin resistance from Staphylococcus epidermidis to methicillin-resistant Staphylococcus aureus associated with failure of mupirocin prophylaxis.
OBJECTIVE
We examined the molecular basis of the emergence of mupirocin resistance in a methicillin-resistant Staphylococcus aureus (MRSA) strain colonizing a nursing home resident undergoing mupirocin prophylaxis.


METHODS
A persistent carrier of mupirocin-susceptible MRSA participated in a trial of mupirocin for nasal decolonization among nursing home residents. During prophylaxis a high-level mupirocin-resistant MRSA emerged in the nasal isolates from this patient. S. aureus and coagulase-negative staphylococci were isolated prior to, during and after 14 days of mupirocin treatment. The staphylococcal isolates and their plasmids were examined by molecular genetic methods.


RESULTS
All mupirocin-susceptible and -resistant MRSA isolates possessed the same genotype. The patient was also colonized by a single mupirocin-resistant Staphylococcus epidermidis strain. The mupirocin-resistant MRSA and S. epidermidis strains harboured identical plasmids that carried the mupA determinant and genes for conjugative DNA transfer in staphylococci. These plasmids could be transferred in vitro from both clinical isolates to S. aureus RN2677.


CONCLUSIONS
The MRSA strain contained a conjugative plasmid expressing mupA that was identical with that found in the S. epidermidis strain which colonized the patient. These findings suggest that transfer of mupA from S. epidermidis to MRSA probably occurred during mupirocin prophylaxis.
Hurdle
Julian G
JG
School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, UK.
O'Neill
Alex J
AJ
Mody
Lona
L
Chopra
Ian
I
Bradley
Suzanne F
SF
D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use; D019072:Antibiotic Prophylaxis; D001426:Bacterial Proteins / Q000235:genetics; D002353:Carrier State / Q000188:drug therapy / Q000382:microbiology; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial; D022761:Gene Transfer, Horizontal; D006801:Humans; D008297:Male; D016106:Methicillin Resistance; D016712:Mupirocin / Q000494:pharmacology / Q000627:therapeutic use*; D009687:Nuclear Proteins / Q000235:genetics; D009735:Nursing Homes; D011815:R Factors / Q000235:genetics / Q000302:isolation & purification; D013203:Staphylococcal Infections / Q000382:microbiology / Q000517:prevention & control*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D009687:Nuclear Proteins; C480380:mupA protein, Staphylococcus aureus; D016712:Mupirocin