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Identification of chromosomal location of mupA gene, encoding low-level mupirocin resistance in staphylococcal
M A Ramsey1, S F Bradley, C A Kauffman
1Division of Infectious Diseases, University of Michigan Medical School, Ann Arbor, USA.
Abstract:
Low- and high-level mupirocin resistance have been reported in Staphylococcus aureus. The expression of plasmid-encoded mupA is responsible for high-level mupirocin resistance. Low-level mupirocin-resistant strains do not contain plasmid-encoded mupA, and a chromosomal location for this gene has not previously been reported. We examined high- and low-level mupirocin-resistant S. aureus strains to determine if mupA was present on the chromosome of low-level-resistant isolates. Southern blot analysis of DNA from four mupirocin-resistant strains identified mupA in both high- and low-level mupirocin-resistant strains. Low-level mupirocin-resistant strains contained a copy of mupA on the chromosome, while the high-level mupirocin-resistant isolate contained a copy of the gene on the plasmid. PCR amplification of genomic DNA from each mupirocin-resistant strain resulted in a 1.65-kb fragment, the predicted product from the intragenic mupA primers. This is the first report of a chromosomal location for the mupA gene conferring low-level mupirocin resistance.
Insights
The mupA gene confers mupirocin resistance in Staphylococcus aureus. This study identifies a chromosomal location for the mupA gene in low-level resistant strains, distinct from the plasmid location in high-level resistant strains.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Mupirocin resistance in Staphylococcus aureus is a growing concern.
- High-level resistance is attributed to plasmid-encoded mupA, but the genetic basis of low-level resistance remains unclear.
- Previous studies have not identified a chromosomal location for the mupA gene in low-level resistant strains.
Purpose of the Study:
- To investigate the genetic basis of low-level mupirocin resistance in Staphylococcus aureus.
- To determine if the mupA gene is present in low-level resistant strains and identify its location.
- To differentiate the genetic mechanisms of high-level versus low-level mupirocin resistance.
Main Methods:
- Analysis of DNA from mupirocin-resistant Staphylococcus aureus strains.
- Southern blot analysis to detect the presence and location of the mupA gene.
- Polymerase Chain Reaction (PCR) amplification using specific primers for the mupA gene.
Main Results:
- The mupA gene was detected in both high- and low-level mupirocin-resistant strains.
- Low-level resistant strains harbored the mupA gene on the chromosome.
- High-level resistant strains possessed the mupA gene on a plasmid.
- PCR confirmed the presence of mupA in all tested resistant strains, yielding a 1.65-kb fragment.
Conclusions:
- This study reports the first identification of a chromosomal location for the mupA gene.
- The chromosomal mupA gene is associated with low-level mupirocin resistance in Staphylococcus aureus.
- Understanding the distinct genetic locations of mupA contributes to comprehending resistance mechanisms.