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Molecular fingerprinting of mupirocin-resistant methicillin-resistant Staphylococcus aureus from a burn unit
E E Udo1, V S Farook, E M Mokadas
1Department of Microbiology, Faculty of Medicine, Kuwait University, Safat, Kuwait. EDET@hsc.kuniv.edu.kw
Objectives:
To characterize mupirocin-resistant methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients in a burn unit by pulsed-field gel electrophoresis and plasmid contents.
Methods:
A total of 53 methicillin-resistant S. aureus, consisting of 48 mupirocin-resistant and 5 mupirocin-susceptible MRSA were compared by plasmid content and pulsed-field gel electrophoresis of Sma I digested genomic DNA.
Results:
Of the 48 mupirocin-resistant isolates, 39 expressed high-level, and 9 expressed low-level mupirocin resistance. Plasmids were detected in all of the 53 isolates; however, only the high-level mupirocin-resistant isolates contained a 38 kb-conjugative plasmid that encoded high-level mupirocin resistance. Pulsed-field gel electrophoresis divided the isolates into four patterns designated types I to IV. Forty-three isolates consisting of 34 high-level, 5 low-level mupirocin-resistant and 4 mupirocin-susceptible isolates defined the type-I pattern. Eight isolates, five high-level and three low-level mupirocin-resistant isolates had the type-II pulsed-field pattern. The type-III and type-IV pulsed-field patterns consisted of a single isolate each. The type-I and type-II pulsed-field patterns were related and only differed by four Sma I bands.
Conclusions:
Results of typing the mupirocin-resistant MRSA from the burn unit with pulsed-field gel electrophoresis indicated that closely related MRSA clones previously circulating in the unit had acquired a high-level mupirocin-resistant plasmid, and spread aided by mupirocin use.
Insights
Mupirocin-resistant MRSA in burn units acquired a high-level resistance plasmid, spreading through related clones. This highlights the impact of mupirocin use on resistance development in MRSA.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat in healthcare settings.
- Mupirocin is a crucial topical antibiotic for treating S. aureus infections, including MRSA.
- The emergence of mupirocin resistance in MRSA necessitates understanding its genetic basis and epidemiology.
Purpose of the Study:
- To molecularly characterize mupirocin-resistant MRSA isolates from a burn unit.
- To investigate the role of plasmids and genetic relatedness in mupirocin resistance.
- To determine the epidemiology of mupirocin resistance in this specific patient population.
Main Methods:
- Pulsed-field gel electrophoresis (PFGE) was employed for strain typing of MRSA isolates.
- Plasmid content analysis was performed on both mupirocin-resistant and susceptible MRSA.
- Genomic DNA was digested with Sma I for PFGE analysis.
Main Results:
- All 53 MRSA isolates harbored plasmids; only high-level mupirocin-resistant strains contained a 38 kb conjugative plasmid.
- PFGE identified four distinct MRSA patterns (types I-IV), with types I and II being closely related.
- The majority of mupirocin-resistant isolates belonged to the prevalent type I or type II PFGE patterns.
Conclusions:
- Closely related MRSA clones in the burn unit acquired a high-level mupirocin resistance plasmid.
- The use of mupirocin likely facilitated the selection and spread of these resistant strains.
- Understanding resistance mechanisms and clonal spread is vital for infection control in burn units.