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Update on mupirocin resistance
1SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA.
Abstract:
Mupirocin inhibits the activity of bacterial isoleucyl-tRNA synthetase resulting in a decrease or cessation of protein synthesis. Expression of resistance in staphylococci has been divided arbitrarily into two groups, low level (minimum inhibitory concentrations [MIC] of between 8 and 256 mg/L) and high level (MICs of > or = 512 mg/L). Low level resistance is associated with spontaneous mutational events, while high level resistance is mediated by a large transferable plasmid. The introduction of a nasal formulation of mupirocin raises many issues concerning staphylococcal breakpoints, since 20,000 mg/L is applied to the mucosal surface to eradicate nasal colonisation with staphylococci, as opposed to eliminating infection. For several years after its introduction reports of resistance in staphylococci were rare. However, the contemporary literature indicates reports of resistance in select populations, particularly associated with dermatology patients. The overall rate of resistance for organisms isolated from the nares is currently unknown. The recent introduction of the E test combined with the 5 microgram screening disk may assist in determining resistance rates in large populations.
Insights
Mupirocin resistance in staphylococci is increasing, particularly in dermatology patients. New testing methods may help track resistance rates in nasal bacteria.
Area of Science:
- Microbiology
- Pharmacology
Background:
- Mupirocin targets bacterial isoleucyl-tRNA synthetase, inhibiting protein synthesis.
- Staphylococcal resistance to mupirocin presents as low-level (mutational) or high-level (plasmid-mediated).
- Nasal mupirocin formulations for eradication raise concerns regarding established resistance breakpoints.
Purpose of the Study:
- To review the emergence and mechanisms of staphylococcal resistance to mupirocin.
- To discuss the implications of nasal mupirocin use on resistance development.
- To highlight the need for accurate resistance monitoring in staphylococci.
Main Methods:
- Literature review of mupirocin resistance in staphylococci.
- Analysis of resistance mechanisms (mutational vs. plasmid-mediated).
- Discussion of clinical implications and diagnostic advancements.
Main Results:
- Mupirocin resistance in staphylococci, initially rare, is increasingly reported, especially in dermatology patients.
- Low-level resistance arises from spontaneous mutations; high-level resistance is plasmid-mediated.
- The efficacy of current breakpoints is questioned due to high-concentration nasal applications.
Conclusions:
- Emerging mupirocin resistance in staphylococci necessitates careful monitoring.
- The E test and screening disks may improve the assessment of resistance rates in nasal isolates.
- Understanding resistance patterns is crucial for effective topical antibiotic use.