Mupirocin-resistant, methicillin-resistant Staphylococcus aureus: does mupirocin remain effective?
OBJECTIVE
To determine the efficacy of mupirocin ointment in reducing nasal colonization with mupirocin-susceptible, methicillin-resistant Staphylococcus aureus (MS MRSA) as well as mupirocin-resistant MRSA (MR MRSA).


METHODS
Prospective evaluation in which patients colonized with MRSA were treated twice daily with 2% topical mupirocin ointment for 5 days.


METHODS
James H. Quillen Veterans' Affairs Medical Center.


METHODS
Forty hospitalized patients with two anterior nares cultures positive for MRSA within a 7-day period.


METHODS
Treated patients had post-treatment cultures at day 3 and weeks 1, 2, and 4. Isolates underwent mupirocin-susceptibility testing and DNA typing. MRSA clearance and type turnover were assessed for isolates that were mupirocin-susceptible, low-level (LL) MR MRSA and high-level (HL) MR MRSA.


RESULTS
Post-treatment nares cultures on day 3 were negative for 78.5%, 80%, and 27.7% of patients with MS MRSA, LL-MR MRSA, and HLMR MRSA, respectively. Sustained culture negativity at 1 to 4 weeks was more common in the MS MRSA group (91%) than in the LL-MR MRSA group (25%) or the HL-MR MRSA group (25%). Positive post-treatment cultures usually showed the same DNA pattern relative to baseline. Plasmid curing of 18 HL-MR MRSA resulted in 15 MS MRSA and 3 LL-MR MRSA.


CONCLUSIONS
Mupirocin was effective in eradicating MS MRSA, but strains of MR MRSA often persisted after treatment. This appeared to reflect treatment failure rather than exogenous recolonization. MR MRSA is now more prevalent and it is appropriate to sample MRSA populations for mupirocin susceptibility prior to incorporating mupirocin into infection control programs.
Walker
Elaine S
ES
James H Quillen Veterans' Affairs Hospital, James H. Quillen College of Medicine, East Tennessee State University, Johnson City 37614, USA.
Vasquez
Jose E
JE
Dula
Roy
R
Bullock
Hollie
H
Sarubbi
Felix A
FA
D000287:Administration, Topical; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000494:pharmacology; D004351:Drug Resistance; D006787:Hospitals, Veterans; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D016712:Mupirocin / Q000008:administration & dosage* / Q000494:pharmacology; D009296:Nasal Cavity / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000188:drug therapy*; D013211:Staphylococcus aureus / Q000187:drug effects*; D013714:Tennessee
D000900:Anti-Bacterial Agents; D016712:Mupirocin