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A plasmid that encodes three genes for resistance to macrolide antibiotics in Staphylococcus aureus
M Matsuoka1, K Endou, H Kobayashi
1Division of Microbiology, Hokkaido College of Pharmacy, Japan.
Abstract:
In previous letters, FEMS Microbiol. Lett. 148 (1997) 91-96, it was demonstrated that plasmid pMS97-obtained from a in 1971 clinically isolated Staphylococcus aureus strain MS8968 resistant to macrolide (Mac) antibiotics--carried an msrA gene and uncharacterized erm gene, respectively. msrA encodes a cytoplasmic membrane protein that mediates the so-called 'active Mac-efflux' (designated hereafter as msrSA') and erm encodes a methyltransferase by which a specific adenine residue of 23S rRNA is modified: methylation prevents Mac antibiotics from binding to the 50S ribosomal subunit. Interestingly, we found, in addition, an mph-like gene (hereafter referred to as mphBM) present together with msrSA' and erm on pMS97. By a BLASTP analysis, the gene mphBM product has 49% identity and 67% similarity to the amino acid sequence of MPH(2')II encoded by mphB from Escherichia coli. The order of genes was 5'-msrSA'-mphBM-3', with a 342-base-pair spacer sequence. Although we have not yet determined where erm gene is located on pMS97, the gene seems to be downstream from mphBM. This finding suggests a warning to us concerning the imprudent use of antibiotics.
Insights
A Staphylococcus aureus plasmid carries macrolide resistance genes, including a novel mph-like gene (mphBM). This discovery highlights the need for caution in antibiotic use to prevent further resistance development.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Macrolide antibiotics are crucial for treating bacterial infections.
- Antibiotic resistance, particularly to macrolides, is a growing global health concern.
- Plasmids are key vectors for the spread of antibiotic resistance genes.
Purpose of the Study:
- To characterize antibiotic resistance genes on plasmid pMS97.
- To identify novel genes contributing to macrolide resistance in Staphylococcus aureus.
- To investigate the genetic organization of resistance determinants on pMS97.
Main Methods:
- Plasmid isolation from Staphylococcus aureus strain MS8968.
- Gene identification and characterization (msrA, erm, mphBM).
- Bioinformatic analysis, including BLASTP for sequence homology.
Main Results:
- Plasmid pMS97 harbors msrA, an uncharacterized erm gene, and a novel mph-like gene, mphBM.
- mphBM shows significant sequence similarity to MPH(2')II from Escherichia coli.
- The identified genes are arranged in the order 5'-msrSA'-mphBM-3' on the plasmid.
Conclusions:
- The presence of multiple macrolide resistance genes on pMS97 contributes to Staphylococcus aureus resistance.
- The discovery of mphBM expands the known repertoire of macrolide resistance mechanisms.
- This finding underscores the importance of judicious antibiotic use to mitigate the spread of antibiotic resistance.