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Decrease in the incidence of mupirocin resistance among methicillin-resistant Staphylococcus aureus in carriers from
Juliana Caierão1, Laura Berquó, Cícero Dias
1Fundação Faculdade Federal de Ciências Médicas de Porto Alegre.
Background:
Methicillin-resistant Staphylococcus aureus (MRSA) is a serious nosocomial problem, globally distributed. Decolonization with mupirocin can be used to control its dissemination.
Objective:
To determine the incidence of mupirocin resistance among MRSA carriers from an intensive care unit.
Methods:
We obtained 2723 nasal swabs during 3 years. Resistance to methicillin and mupirocin were verified (agar diffusion and the E test) and confirmed by polymerase chain reaction (PCR) (mecA for methicillin; ileS-2 and mupA for mupirocin). Plasmid-curing procedure and pulsed-field gel electrophoresis (PFGE) were employed in isolates exhibiting high resistance to mupirocin (HR-Mup) and in other selected organisms.
Results:
The overall incidence of HR-Mup among MRSA carriers during the studied period was 4.84% (8/165); however, the incidence decreased from 13.04% (6/46) in the first year to 3.5% (2/57) in the second year and was 0% in the last year (P = .02). LR-Mup, in contrast, increased significantly (P = .01).
Conclusion:
Plasmid-curing procedure showed the plasmid location of genes responsible for HR-Mup. PFGE demonstrated that most MRSA, including the isolates with HR-Mup, were genetically related. The decline in HR-Mup may be attributable to the plasmid location of genes (ileS-2/mupA) and to the fact that all patients colonized with HR-Mup MRSA died or were discharged in a relatively short period of time.
Insights
High-level mupirocin resistance in Methicillin-resistant Staphylococcus aureus (MRSA) carriers decreased significantly over three years in an ICU. This decline in mupirocin resistance may be linked to plasmid-located resistance genes and patient outcomes.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Hospital Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant global healthcare challenge.
- Mupirocin is a key agent for MRSA decolonization and infection control.
Purpose of the Study:
- To investigate the incidence of mupirocin resistance among MRSA carriers within an intensive care unit (ICU).
Main Methods:
- Analysis of 2723 nasal swabs collected over three years.
- Verification of methicillin and mupirocin resistance using agar diffusion, E test, and PCR (mecA, ileS-2, mupA).
- Plasmid-curing and pulsed-field gel electrophoresis (PFGE) were performed on high-resistance isolates.
Main Results:
- Overall high-level mupirocin resistance (HR-Mup) incidence was 4.84% among MRSA carriers.
- HR-Mup incidence significantly decreased from 13.04% in year 1 to 0% in year 3 (P = .02).
- Low-level mupirocin resistance (LR-Mup) showed a significant increase (P = .01).
Conclusions:
- Genes conferring HR-Mup (ileS-2/mupA) are located on plasmids.
- Most MRSA isolates, including HR-Mup strains, were genetically related.
- The observed decline in HR-Mup is likely due to plasmid-mediated resistance and rapid patient turnover.
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