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Molecular evolution of tetracycline-resistance plasmids carrying TetM found in Neisseria gonorrhoeae from different
D M Gascoyne1, J Heritage, P M Hawkey
1Department of Microbiology, University of Leeds, UK.
Abstract:
High level tetracycline resistant strains of Neisseria gonorrhoeae (TRNG) have been shown to carry a 40.6 kb (25.2 MDa) conjugative plasmid with a Class M tetracycline resistance determinant. Restriction endonuclease analysis mapping showed that there were at least two different TRNG plasmid types which were found in geographically distinct locations. The physical maps of these two plasmids were compared to a gonococcal conjugative plasmid which did not encode tetracycline resistance. The plasmid type which is endemic in the Netherlands was found to be closely related to the gonococcal conjugative plasmid, which supports the established hypothesis that the 40.6 kb plasmid has evolved by transposition of the TetM determinant into the conjugative plasmid. The plasmid found in the United States has either evolved by substantial divergent evolution or it results from a different transposition event. In the UK there have been isolations of TRNGs carrying either of the two plasmid types reflecting a flow of people both across the Atlantic and in Europe. It is possible that further TetM-containing plasmids will be found in N. gonorrhoeae paralleling the family of TEM beta-lactamase encoding plasmids already described.
Insights
High-level tetracycline-resistant Neisseria gonorrhoeae strains harbor a conjugative plasmid with a TetM determinant. Two distinct plasmid types exist, suggesting evolution via transposition events and international spread.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- High-level tetracycline resistance in Neisseria gonorrhoeae (TRNG) is often mediated by a 40.6 kb conjugative plasmid.
- This plasmid carries a Class M tetracycline resistance determinant (TetM).
Purpose of the Study:
- To compare the physical maps of different TRNG plasmid types.
- To investigate the evolutionary origins of these plasmids.
- To understand the geographical distribution and spread of TRNG.
Main Methods:
- Restriction endonuclease analysis and physical mapping of TRNG plasmids.
- Comparison of TRNG plasmid maps with a non-tetracycline-resistant gonococcal conjugative plasmid.
Main Results:
- At least two distinct TRNG plasmid types were identified in geographically separate locations.
- The plasmid type prevalent in the Netherlands is closely related to the non-resistant gonococcal conjugative plasmid, supporting evolution by TetM determinant transposition.
- The plasmid type found in the United States suggests either significant divergent evolution or a separate transposition event.
- Isolations of both plasmid types in the UK indicate international and European population movement.
Conclusions:
- The 40.6 kb plasmid in Neisseria gonorrhoeae likely evolved through transposition of the TetM determinant into a conjugative plasmid.
- Distinct evolutionary pathways or multiple transposition events may explain observed plasmid diversity.
- The findings highlight the global spread of antibiotic resistance and suggest potential for further discovery of similar plasmids.