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Nucleotide sequences specific for Tn1545-like conjugative transposons in pneumococci and staphylococci resistant to
C Poyart-Salmeron1, P Trieu-Cuot, C Carlier
1Unité des Agents Antibactériens, Institut Pasteur, Paris, France.
Abstract:
The distributions of tet(M) and conjugative transposons related to Tn1545 were studied by hybridization in 47 clinical isolates of Streptococcus pneumoniae resistant to tetracycline. Resistance to tetracycline was always associated with resistance to minocycline and was due to the presence of the tet(M) gene. Association of tet(M) with int-Tn, the gene encoding the protein required for the movements of Tn1545-like transposons, was found in all but one strain of S. pneumoniae. In contrast, int-Tn was detected in only 2 of 37 strains of Staphylococcus spp. harboring tet(M).
Insights
Tetracycline resistance in Streptococcus pneumoniae is linked to the tet(M) gene and often involves mobile genetic elements like Tn1545-like transposons. This genetic element, int-Tn, was frequently found in resistant S. pneumoniae but rarely in Staphylococcus species with tet(M).
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Tetracycline resistance is a growing public health concern.
- The tet(M) gene is a common determinant of tetracycline resistance.
- Conjugative transposons, such as Tn1545, facilitate the spread of antibiotic resistance genes.
Purpose of the Study:
- To investigate the distribution of the tet(M) gene and Tn1545-like conjugative transposons in tetracycline-resistant Streptococcus pneumoniae.
- To compare the genetic context of tet(M) in S. pneumoniae with that in Staphylococcus species.
Main Methods:
- Hybridization techniques were used to detect the presence of tet(M) and int-Tn.
- The study analyzed 47 clinical isolates of Streptococcus pneumoniae and 37 strains of Staphylococcus spp. resistant to tetracycline.
Main Results:
- All tetracycline-resistant S. pneumoniae isolates possessed the tet(M) gene, which was also associated with minocycline resistance.
- The int-Tn gene, essential for Tn1545-like transposon mobility, was found in all but one S. pneumoniae isolate.
- In contrast, int-Tn was detected in only 2 out of 37 tetracycline-resistant Staphylococcus isolates carrying tet(M).
Conclusions:
- The tet(M) gene is the primary cause of tetracycline and minocycline resistance in the studied S. pneumoniae.
- Tn1545-like transposons appear to be widely distributed and efficiently mobilized in S. pneumoniae clinical isolates.
- The genetic environment and mobility of tet(M) differ significantly between S. pneumoniae and Staphylococcus species.